One of the three pillars of photography that can dramatically affect the look of your images is camera ISO (the other two being shutter speed and aperture). Like those two settings, ISO controls the brightness of your photos, and it is a crucial setting to use properly if you want to take the best possible images. In this chapter of Photography Basics article, we will explain ISO using simple language and examples so that you can make the most of it for your own photography.
What is ISO?
In very basic terms, ISO is simply a camera setting that will brighten or darken a photo. As you increase your ISO number, your photos will grow progressively brighter. For that reason, ISO is a good tool to help you capture images in dark environments or be more flexible about your aperture and shutter speed settings.
However, raising your ISO has consequences. A photo taken at too high of an ISO will show a lot of grain, also known as noise, and might not be usable. So, brightening a photo via ISO is always a trade-off. You should only raise your ISO when you are unable to brighten the photo via shutter speed or aperture instead (for example, if using a longer shutter speed would cause your subject to be blurry).
Common ISO Values
Every camera has a different range of ISO values (sometimes called ISO speeds) that you can use. A common set is as follows:
- ISO 100 (low ISO)
- ISO 200
- ISO 400
- ISO 800
- ISO 1600
- ISO 3200
- ISO 6400 (high ISO)
Quite simply, when you double your ISO speed, you are doubling the brightness of the photo. So, a photo at ISO 400 will be twice brighter than ISO 200, which will be twice brighter than ISO 100.
What is Base ISO?
The lowest native ISO on your camera is your “base ISO”. This is a very important setting, because it gives you the potential to produce the highest image quality, minimizing the visibility of noise as much as possible. Some older DSLRs and a number of modern cameras, such as the Fuji X-T2 have a base ISO of 200, whereas most modern digital cameras have a base ISO of 100. Optimally, you should always try to stick to the base ISO to get the highest image quality. However, it is not always possible to do so, especially when working in low-light conditions.
Side note:
Some cameras have extended “HI” and “LO” values for ISO that might stretch beyond their native range. However, these are completely simulated and lower your image quality. We recommend avoiding them.
Low vs High ISO Noise Visibility
To give an example of two photos taken at different ISO values, take a look at the comparison below. Pay attention to the level of noise (graininess and blotchy colors) in the images:
The difference is clear – the image at ISO 3200 has much more noise than the one at ISO 200 (which I brightened with a long shutter speed instead). This is why you should avoid high ISOs whenever possible, unless conditions require you to use them.
How to Change ISO
Changing your ISO varies from camera to camera. Here are some common ways to change ISO:
- To start, enter a mode that lets you select the ISO yourself. Get out of Auto mode, and go to Manual, Shutter Priority, Aperture Priority, or Program (we tend to prefer Aperture Priority or Manual).
- For entry-level DSLRs and mirrorless cameras, you probably need to open a menu (possibly the “quick menu”) and find the section for ISO. Select the value you want, or set it to Auto.
- For higher-end cameras, there may be a dedicated “ISO” button on the camera. Press it while spinning one of the wheels to change your ISO setting. If you don’t see a button labeled “ISO”, it is still possible that your camera will let you program one to perform this task.
- Other cameras may have a dedicated wheel that already has various ISO settings marked. This makes things even easier.
Check your camera manual if you still aren’t sure. However, it is worth being very familiar with how to change your ISO setting quickly, since it’s something you will likely be adjusting quite often, especially if you shoot in low light conditions without a tripod or flash.
What ISO Should You Use?
Many photographers understand the basics of ISO, but they aren’t sure which ISO value to actually pick in the field. In practice, there’s a reason why your camera allows such a wide range of ISO settings: Different situations call for different ISOs. Below, we will cover some of the common scenarios you may come across.
When to Use Low ISO
As discussed above, you should always try to stick to the lowest ISO (base ISO) of your camera, which is typically ISO 100 or 200, whenever you can. If there is plenty of light, you are free to use a low ISO and minimize the appearance of noise as much as possible.
Even in dim or dark environments, you still might be able to use a low ISO. For example, if you have your camera mounted on a tripod or sitting completely still on a table. In that case, you can safely use a low ISO and brighten your photo via a long shutter speed instead, since you won’t introduce camera shake. However, keep in mind that if your camera does use a long shutter speed, anything that is moving will look like a ghost:
Just kidding, of course! That’s my lovely nephew being the subject of my long exposure test. I set the camera to the lowest ISO to retain the detail, which required a long shutter speed of five seconds in order to capture a bright enough photo. My nephew sat still, while my friend stepped in for a brief moment to introduce the ghost :)
When to Use High ISO
Even though it is ideal to use low ISOs, there will be plenty of times when a high ISO is necessary in order to take a good photo in the first place. The simple reason is that you are often fighting against motion blur, and you will need to pick between a sharp photo at a high ISO, or a blurry photo at a low ISO. Take a look at the image below:
I captured these Black Skimmers at 1/2000th of a second and ISO 800. Here, my camera needed 1/2000th of a second to fully freeze the birds while they were in flight. What would have happened if I had set ISO 100 on my camera instead? I would have needed a shutter speed of 1/250th of a second to capture a bright photo. At that setting, there would have been a lot of unwanted motion blur in the picture, since the birds were moving so fast. In short, I would have ruined the picture.
The bottom line is that you should increase the ISO when there is not enough light for the camera to capture a sharp, bright photo any other way. When I shoot handheld photos indoors without a flash, I always set my ISO to a higher number to capture the moment without introducing blur. Or, when photographing ultra-fast action like in the bird picture above, raising your ISO is often necessary.
On most cameras, there is a setting for Auto ISO, which works great in low-light environments. The beauty of this setting is that you input the maximum ISO you are willing to use, so that the camera does not cross that limit. Personally, if I want to limit the amount of noise in a photo, I will set my maximum ISO to something like ISO 800, 1600, or 3200. The downside is that the camera will start using progressively longer shutter speeds if it reaches these ISO limits, which leads to more motion blur. Everything is a trade-off!
Minimizing Noise and Maximizing Image Quality
Some photographers think that the best way to capture high-quality images is to use Base ISO 100% of the time. However, as demonstrated above, that simply is not true. Sometimes, you’ll be in dark environments when you have no choice but to use a higher ISO.
You should only use base ISO when there is enough light to do so. Don’t try to force ISO 100 in a dark environment, or your photos will come out way too dark. Similarly, if you’re using a fast shutter speed to capture action, it’s essentially the same as taking pictures in a dark environment (since you strictly limit the amount of time your camera sensor is able to capture light). So, for certain types of sports and action photography, a high ISO might be your only option.
To maximize your image quality, here are the four steps you need to follow:
- Select the aperture setting that will provide your desired depth of field.
- Set your ISO to its base value, and put your shutter speed to whatever setting provides a proper exposure.
- If your subject is blurry, progressively raise your ISO and use a faster shutter speed until motion blur disappears.
- If your ISO is getting too high and you still have the ability to use a wider aperture, open it up until the ISO gets to a more manageable level, even if it means sacrificing some of your desired depth of field.
That’s all it takes! If you follow these steps, you’ll capture the maximum image quality each time. You’ll find the ideal balance between noise, motion blur, and depth of field.
Common ISO Myths and Misconceptions
ISO has a lot of myths surrounding it, including some that are quite common to hear. In this section, we will quickly address some of those concerns so that you are not misled about this topic in the future.
Is ISO “Sensor Sensitivity”?
This is the most common myth related to ISO. It is something you will see all over the web (and in print). However, although it may help you to think of ISO as “acting like” camera sensor sensitivity, that’s not what it actually does. Instead, digital sensors only have a single sensitivity, regardless of your ISO. It is more accurate to say that ISO is like a mapping to tell your camera how bright the output photo should be, given a particular input exposure.
Is ISO Part of Exposure?
No, ISO is not part of exposure. Shutter Speed and Aperture brighten your photo by physically capturing more light. ISO doesn’t do that; instead, it essentially brightens the photo you already captured. So, photographers don’t consider it to be a component of exposure.
Is Raising ISO Just Like Brightening Your Photo on a Computer?
This is a clever question, but, again, it is simply a misconception. Brightening a photo on your computer can act in many ways like raising your ISO, since it does make noise more visible (and it leads to a brighter image). But the simple difference is that raising your ISO in the camera nearly always provides better image quality than brightening a photo on your computer. In other words, it is better to use ISO 800 when necessary, rather than brightening an ISO 100 photo to a huge degree in post-processing software like Lightroom!
Conclusion
If you have any questions, comments or feedback, please post them in the comments section below.
If you have enjoyed this article, please check out our in-depth Level 1 Photography Basics Course, where we explore all the basics of photography in much more detail. It is an intensive, 5+ hour course with enough material to not only get you started today, but also to serve as a reference material in the future.
on a d700 would you go up to 6400 iso in dark conditions, or would that be to grainy? Specifically on the auto iso feature, should I do 200-3200 or 200-6400. The reason I ask is because I had it on 200-6400 and I was taking some pictures in my house without the flash in a room lit by lamps and the auto iso was going all the way up to 6400. I was thinking going up to 6400 would be in almost pitch black conditions.
Monty, it really depends on what noise levels are “acceptable” to you. I personally set my Auto ISO to 200-1600, but in some situations increase it to 3200 (if my shutter speed is too low). I rarely increase it to 6400, because the noise starts affecting the sharpness of the image and I do not like it.
Hope this helps :)
Nasin – Your website on DSLRs is, by far, the easiest to understand and most informative! Thanks for sharing your jewels of wisdom!
Refering to the “Black Skimmers” photo above, do you have any rule of thumb for using a tripod when shooting wildlife scenes at different times of the day or, is it a matter of preference? Will a tripod help eliminate any unwanted motion blur or, will my camera’s shutter speed be fast enough to make this a non-issue?
Thanks in advance!
Tom, thank you for your valuable feedback, I appreciate it!
The image of black skimmers was taken hand-held. If you use fast enough of a shutter speed (preferably above 1/1000th for birds), you do not need to use a tripod to freeze action.
Hi Nasim,
You really did incredible work for beginners like me. I have one question, I am trying to take my nephews pictures. he is 3 moths old. i tried all your tips for shutter speed, aperture and ISO also. it works well but pictures are not sharp enough. shows some blur when he move is hand. and My problem is i cant keep him stable. I am using Nikon D3000 18-55 VR lens. i have 70-300 lens and tripod also. all pictures taken inside.
Let me know if you have any solution for it
Thanks
Pankaj, if you are seeing blur while the child moves, it means that your shutter speed is still too slow. The only option is to either increase the light in the room (by opening doors/windows) or using flash.
Oh, this particular exchange reminds me so much of why we bought a DSLR in the first place: My wife got tired of pointing the camera at kids and pressing the button; while the camera decided on its own good time when to expose the image, the kids moved off somewhere else, and we got a nice picture of our carpet. A Nikon D50 fixed that… :D
Back to the thread: Nasim, I really like your articles – they do an excellent job of abstracting these sometimes daunting topics to a level digestible by folks more interested in making good images than in how the underlying stuff does its thing. For those with a modicum of electrical knowledge, I think pointing out that ISO-setting is equivalent to turning a volume knob on an audio amplifier – it controls the amount of amplification AFTER the signal is detected. That’s the realization that got me past most of the misconceptions.
Just curious…By raising the ISO, Why would anyone want noise in their photos to begin with? is there a way of getting rid of that grain? How were you able to capture that image of that bird at a higher ISo and not see the grain?
Thank you
Seher, I apologize for such a late response – I somehow missed your comment. It is not that one would “want” noise in their images. Everybody obviously prefers to have noise-free images. I would not mind being able to shoot in the dark and have grain-free images :)
However, even the most advanced sensor technology cannot yet reach noise-free levels. We have gotten very far with today’s technology, which has already surpassed film by a huge margin, but there are limits to everything, including sensor’s ability to collect light quickly without any artifacts.
As for the bird image, there are many programs you can find online that can “clean up” noise from digital cameras. Adobe Lightroom, for example, has a built-in capability to do this.
Did you clean up noise in you black skimmer capture?
I wasn’t paying attention to dates! I am just shy of a decade late and a dollar short! Sorry,
Nope! It doesn’t look very good at 100% zoom, but for web output, it looks perfectly fine. If I were to print it, I would definitely clean up noise though…
And no worries about the dates – this article has been rewritten and we kept some of the useful comments for other readers.
I am wondering what calculation is used to determine Shutter Speed?
Assuming is a fantastic day and you have PLENTY of light, and you are in Av mode,
does it simply pick the lowest possible ISO and then calculate the Shutter Speed based Metering of Neutral Grey and assuming 18% Reflectance..
I am not sure if that question is more technical than it should be or if i am just exposing my ignorance.. Sorry!
Wesley, I apologize for a late response. The calculation of Shutter Speed depends on many variables, such as exposure mode (Auto, Aperture Priority, Shutter Priority, etc), metering mode (Evaluative, Spot, Area) and aperture + ISO values. If your camera is equipped with an “Auto ISO” feature, the camera will change the shutter speed based on pre-defined values in the camera menu. If you do not have such a feature, then the ISO value will be whatever is set on the camera (normally base ISO such as 100) and the shutter speed will be automatically determined by the exposure meter on the camera.
Hi Nasim,
I have a Nikon D3100 and started photographing a lot lately. I did some potrait photography of my son outdoor suring noon time and partly shady.
I used the A priority mode and set it in Auto like suggested and the Max ISO= 800, Min Shutter speed = 1/500.
The photos cmae out good, but i found a lot of noise which i had to remove in Lightroom following your “removing noise in lightroom” article.
1) Would there be lot of post proessing involved if we shoot in higer ISO? or does it depend on the Camera model and sensor?
2) Your above images seem to be exceptionally sharp considering being shot @ ISO 800. Was the post processing involved?
3) Is it a bad idea to keep the ISO @ 100 0r ISO 200 for getting low noise and good images.
JP,
1) It depends on how comfortable you are with noise. If it bothers you, then yes, there would be plenty of work involved.
2) When you resize images for the web, they tend to show much less noise. If I showed you images at 100%, you will definitely see more noise. In addition, the image you are referring to was shot on a full-frame camera, which handles noise much better than a DX camera.
3) No, that’s actually what you want to do – try to keep ISO low all the time, to get the best images. However, in some low-light situations you have to increase ISO or your images will be blurry.
Love your article on ISO Nasim! I am going to experiment the ghost shot today ;)
i need to practice that shot too
Hi, I’ve been photographing for a good many years, but have always used Auto settings and find that too often I have too much grain in my shots, I’ve got to be honest and say I’ve been too ”lay back” about learning the technique’s about good photography, or should i say really trying to understand it. I have been told many times that I have a special eye for photo’s but I know deep in my heart that I could do much better ,and then get out and try to become a professional. But that needs work and dedication and I have decided to do that. The first step was to google my question what is ISo in photography. I found you… and I appreciate what you have put up here, now to get going. Thanks for your care to be willing to put time and effort into sites such as yours. I appreciate it.
Kind regards, Karen.
OK, pay attention closely. You need to think of ISO as building a picture using bricks. At ISO 100 it may take 1000 bricks to make an image. At ISO 200 you halve the number of bricks to 500. At ISO 400 you halve the number of bricks again to 125 bricks to make that image. etc. etc. By the time you get to 3200 you have very few bricks to work with so there is no possible way you can get the detail or saturation even with “interpolation”.
There is no free lunch here! You are just trading resolution, detail, contrast, and saturation for shutter speeds or fstops.
Set your camera to ISO 100 or 200 and leave it there if you want maximum resolution, detail, contrast, and saturation. Don’t be lazy. Use stabilization where necessary!
I take people walking in the woods all the time as a guide. Many have expensive SLRs. They may look down their nose at my Canon G12 (how wrong they are). Many figure that their pics will be better if they have a more expensive camera. WRONG! It’s dark in the woods. I see them set to auto everything. When their walk is over my pics are always better than theirs. How does that work? I know photography and I know my camera.
Learn the basics. Even with the magic cameras we have now, a camera is still just a box with a lens, an aperture, and a door that opens and closes. These relationships are necessary to understand if you want to become truly good. Cameras don’t take pictures! People do!
David,
I appreciate the response and the excellent tutorial on ISO and the importance of basics. Actually I have been shooting for many years (too many, I’m 58) but not with a camera with Auto ISO. I’ve shot MF, range finders and digital SLR’s, most recently a Canon 1Ds Mark II. The reason for my post is that I have a new Nikon D800 and that there are a million settings and so far I haven’t figured out how they all work. That’s especially true with Auto ISO, which seems very convenient but perhaps too unpredictable. I’m really trying to decide whether to turn the thing off and handle ISO manually like I’ve always done.
Thanks again.
Mike
Sensor science—Each pixel is an electrical switch. At the “native” ISO setting, when a photon hits a pixel, that pixel registers “yes, light!” And it is very accurate. At native ISO, all works well, the sensor differentiates black and white, red and purple, etc. When that sensor is pushed past it’s native (most accurate) signaling, each pixel has to decide “thumbs up or thumbs down?” IE “Was that a photon….or not….” in effect, each pixel is struggling to make the right decision. So, with perhaps thousands upon thousands of the wrong decisions, you get NOISE!
I’ve been searching all day for explanations on ISO, Aperture and Shutter Speeds and your 3 articles have been the easiest to understand! Thank you!!!!!
Excellent explanation, easy to understand and very informative for a beginner like me. Keep up the great work on your site. I’m loving it!
Thanks for this guide – I enjoy photography, but low level, more hobbyist. I live in Scotland however and am blessed with stunning scenery all around. Currently on holiday in Appin, in the North West Highlands, and have my trusty camera Nikon Coolpix S6100 (low budget, but good pics) to hand! Also picked up Sony Xperia Z1 Compact that comes with a very decent 20MP camera onboard. Will enjoy loading up on some good shots and now I understand what the heck ISO is all about, I’ll be sure to mess around a little more. Plan is to get a slightly better camera in the next year or so, but for now, it’s fun.
this doesn’t apply to shooting in RAW, true? There is no noise, even with a super-high iso, especially on a camera like the 6d, 5d, etc..
Incorrect- There is always going to be noise if you set your ISO to extremely high values (say around 3200-6400 and above) even in the highest ends of cameras. However, typically, the more expensive the camera, the better it’s ISO performance. This is one of the most expensive features of your camera, and what a lot of your money is going into when buying a camera.
I have browsed through articles on the Internet regarding the above subject however none of them was able to explain it like you did. Thank you so much.
So when you have a setting with a lot of light such as your beautiful bird image, it is less likely that there will be a lot of noise? So generally in settings with a lot of light it is ok to increase the ISO? What about when you’re shooting a close up image in a setting with a lot of light what should the ISO be?
If there isn’t much motion, set it to the base ISO (100-200)
I have been confused of this for a long time…. I want to use a low iso, but it makes my pictures very dark and my shutter speed slows. If I turn it up it increases the noise and lowers the quality. Am I missing something? I use a Canon Rebel t3
Your either not getting enough light or your Aperture (F-stop) setting it set too high. You can always use flash to overcome any low-light situation but that can unnatural glow to your photographs, that you may not like.
Not many cameras can shoot in low light at very low ISO. The ISO there setting is there to help you get pictures that you normally could not get in low light. The only thing you can do if your pictures turn out dark is to make sure your Aperture setting is as low as it goes(this is usually done automatically unless you are in a manual mode). After that use the slowest possible Shutter speed until your pictures get bright enough to satisfy you. With practice you will be able to find what settings you need for most situations.
Here are what ISO is about:
_Base ISO (lowest ISO) produces best image qualify with default amount of light, which also means it takes time. It is best for outdoor photos.
_Higher ISO produces poorer image quality with a great of amount of light results in noise.
_However, if you want to take a steady shot of a moving object like birds or cars, you need to set ISO higher to help the speed of image production.
Please correct me if I’m wrong.
Thank you so much for that explanation. I recently took a photography course and I was still unclear on ISO. You explanation was perfect, I feel much more confident with this information.
I am totally a beginner about cameras. The only thing I know about cameras is that Optical zooming is better than digital zooming in terms of capturing far-away views like landscapes, an aircraft or other objects at far distance. This conclusion is based on how phone cameras being digital unable to capture distanced objects as they get faded. but with optical zooming, one can capture a distanced object with maximum clarity. Even in optical zoom cameras, there are two types if i am not wrong. one is like auto zooming and the other is manual zooming where one has to spine the lens. I have to learn more about that. I have to learn more about bridge cameras and mirror less cameras like Sony alpha a6000. I like to photograph so i will like to go with manual photography where I can adjust the lens according to the distance and the object. You may guide me better assisting me on all above features that I am trying to learn before I buy a good camera. Thanks
This was very helpful! the first I fully understand ISO (and learn how to do the calculation between ISO, Shutter Speed). Thank you very much!
regards
Raber
I come from a period in time when everything was film. I have used sheet film (b & w) in 4×5 Crown Grafic and roll film ( 35mm and 21/4 x 2/14) in Pentax K1000 etc. When digital came along it was like learning photography all over again. ISO vs ASA and the newer digital lenses as well.
Your various explanations have been most helpful and I thank you very much.
I googled “what does aperture mean” and got the link to your explanation of that. I am now reading all your tutorials as you are great at explaining this stuff! I have wanted to get into armature photography forever, and just got a stunning new camera for my birthday, but no idea how to use it properly. Your website is so helpful!!!
Why would you ever need something like this :
ISO 100–32000 (expandable to 50–102400)
What would you ever use such a high ISO for?
Robert, such extremely high ISOs are often useless, since there is too much noise. However, when an image is resized and made much smaller say for the web viewing (a process often referred to as “downsampling”), the amount of noise can look acceptable even at very high ISOs such as ISO 25,600.
Hi I’m lost, why do photographers say 1/100th or 1/2000th? What’s that mean?
This is a reference to the shutter speed of the camera. It is how fast the shutter opens and closes when you take the picture. Imagine you are taking a picture of a helicopter flying overhead. The rotor on the helicopter is spinning at 6000 rpm (if you do the math that is 100 times per second). If you were to take a picture of this helicopter at say 1/8 shutter speed, the shutter will remain open for 125 ms (milliseconds) or 1/8th of a second in which time the rotors on the helicopter would have moved around approx. 12-1/2 revolutions, giving you a blurred picture of the rotors. Now if you were to take that same photo at 1/2000 shutter speed, you would practically stop the motion of the rotors altogether. So the helicopter would appear to be just suspended there in the air with no motion showing via the rotors. In essence, you can stop motion by going with a higher shutter speed. To stop the speed of a basketball being shot towards the hoop might require a shutter speed of 1/250, whereas to stop the wings of a hummingbird in flight might require a speed of 1/4000. But this is the basic concept of shutter speed.
In technical terms, ISO is really gain. It gets dialled in and then guides us what aperture and shutter speed we use. But it has no direct effect on the RAW file. The gain is applied when we process the RAW file later. Shutter speed and aperture is what controls the light that is recorded. The gain or ISO (which requires an amplifier that has noise and amplifies noise), whether applied before or after, should be as little as possible. Rule is simple, capture as much light as possible and use as little gain as possible. The ISO is a tool to deal with that.
I stopped reading at some points where I found that the idea of simplifying the ISO explanation is leading to wrong conclusions. Usually I agree on many of your articles, Nasim, but this time we have a different conception.
But then, people reading the “basics” here, ask question like the one about 1/100 or 1/2000 not knowing the relation to shutter speed, so I wonder on which base we are discussing.
First you say “In very basic terms, ISO is simply a camera setting that will brighten or darken a photo”. Later you say “Shutter Speed and Aperture brighten your photo by physically capturing more light. ISO doesn’t do that; instead, it essentially brightens the photo you already captured.”
ISO is afaik not a post capture treatment, it is essentially already part of the capture. As there are also sensors with more than one base ISO (like the one of the D850), the ISO setting leads to two different circuits and only one is activated to catch a high or low ISO frame.
Your question “Is ISO “Sensor Sensitivity”?” (No, and I agree with your answer) should be followed up by the question “Is ISO amplifying the information coming out of the sensor?”. I don’t see ISO as a kind of mapping where you can shift a dark to a bright picture without loosing anything. I see it as an amplification process of what shutter and aperture captured.
That makes sense because by raising the amplification the sensitivity does not change. Brightness increses and because of amplification effects also the noise.
Your statement “No, that’s actually what you want to do – try to keep ISO low all the time, to get the best images” is something I disagree with very much. Noise is highly overrated in this general statement. It IS important to keep the noise down if you want to show as much details as possible – but a “best image” is absolutely not depending on the success in getting very low noise. The lowest possible ISO can easily be 6400. It doens’t make sense to raise ISO for a “just in case scenario” – but it also doesn’t make sense to get motion-blurred pictures and becoming proud of “yes, you can’t recognize the animal but the noise was very low, and that’s what makes a great picture, ask Nasim” :))
And what to say about Auto-ISO? I’m always hesitating to rely too much on automatic, but these days ISO automatic can consider focal length to not slow down shutter speed very effectively. Most of the time I use Auto ISO except I’m sure I need something different or I know the camera is on a tripod.
Joachim, thank you for your feedback, we really appreciate it. The original article on ISO talked about ISO being “sensitivity”, similar to what you see on many other resources. I found that ISO sensitivity was very easy to explain for a beginner, especially those who have shot with film before, but always struggled with the fact that it was wrong to explain it that way. As Spencer and I looked at the ISO article again, we decided to take a different approach this time and see how easy it would be to try to explain it the right way. We had to exclude a number of things from the beginner ISO article, including ISO gain, invariance, dynamic range and other relevant topics. The idea was to keep everything simple enough for anyone to understand, especially those who have no idea about camera basics.
You have to agree that we cannot talk about certain one-offs in the industry, such as the Nikon D850 or the GFX 50S (which exhibits similar behavior at higher ISOs) when talking about ISO overall. As for amplification, that’s the word I did not even want to have in the first place, because it means so many different things to people who are not familiar with cameras. How can we keep this topic basic and simple without introducing the difficult jargon? That’s the tough part – if you have any ideas about how to make it easy and yet accurate, we would love to welcome it – I am very open to changing the article. In fact, at this time we are still working on the language, so we can revise the article as needed.
As for keeping ISO low to get the best out of images, please read the whole article. We list specific reasons when ISO needs to be increased, such as when motion blur needs to be removed from images. Unless you are dealing with a moving subject, or moving camera, it is best to keep ISO as close to its base ISO as possible.
Auto ISO is great and we have a separate article that covers it in detail :)
Once again, thank you for your valuable feedback and I am looking forward to your reply.
Hello Nasim, thanks a lot for taking the time to reply.
Keep it simple is a nice idea, but is simple not more complicated? I just think on keep ISO as low as possible – yes, agreed, but with that a lot of inconveniences destroying the simple concept. Amplifying the output of a sensor to me is like an anlogy of amplifying the output of a microphone which has the (sort of) same downsides. If you push it too much, noise increases – int he picture or recording? In both, of course.
I think the analogy microphone / sensor is not worse than my information overdose with two layer sensors or whatever. A more simple recipe – as I see it – will just lead to more half-knowledge and misleading ideas. The sensitivity (the given base ISO) is not touched by the fact that before the camera writes the received information to the memory card, something happens in between the process of catching the given amount of light. Which is a cooperation of aperture and shutter speed. And that amount is only the “right” amount at base ISO, but in some cases we need different settings of shutter speed and aperture – and ISO is the adjustment know to move in that moment.
The simplest could be: Use Auto-ISO and don’t bother much about as a beginner. Auto-ISO will avoid some problems and rarely lead to bad image quallity.
Hi Nasim,
“if you have any ideas about how to make it easy and yet accurate, we would love to welcome it”
If you want to introduce a notion of amplification, their is one analogy you can use maybe. The one of the car radio:
Iso is exactly like the volume button on your radio. You can make the sound louder (=> picture brighter) but if the reception is bad (=> low light) increasing the volume will not do any good, it will increase also the noise, the shuuuuuuu, (=> picture noise) on top of your music.
Dear Joachim,
Here is actual measured noise data for a modern Sony sensor in a recent camera. As you can see electronic noise is reduced with ISO going up:
ISO Shadow Noise, e-
50 4.84
64 4.45
80 4.27
100 4.98
125 4.56
160 4.19
200 3.94
250 3.23
320 2.62
400 2.18
500 1.82
640 1.51
800 1.29
1000 1.26
1250 1.24
1600 1.22
2000 1.21
2500 1.20
3200 1.19
4000 1.15
5000 1.12
6400 1.09
8000 1.06
10000 1.04
12800 1.02
16000 1.02
20000 1.02
25600 1.02
32000 0.71
40000 0.70
51200 0.69
64000 0.68
80000 0.67
102400 0.68
“e-” is not a measure of the noise, but the number of photons collected per raw level: the bigger the better. For a treatise see: theory.uchicago.edu/~ejm/…se-p3.html
i for one dun think ISO is about “how bright or dark” the photo is. if it was solely a matter of pushing up or down the brightness, then transposing the entire data would work without introducing noise.
I’ve always thought ISO is akin to setting the threshold in which a sensor pixel will register signal as positive and write it onto the file
(all number used are for illustration purposes only)
for example, at ISO 100, the sensor pixel requires 1000 photons to register a reading. this means that adjacent sensor pixel which is supposed to be black would not register a reading if only 500 stray photons hits those adjacent sensor.
in dark conditions where the maximum photons my sensor pixel can expect to get is 600, then none of the sensor would fire at ISO 100 thus picture is dark. so I turn up my as ISO and the threshold becomes lower, say 500. this would allow it to register a reading with 600 photons but the side effect is that the stray 500 photons that we talked about earlier has a greater probability of registering a false positive reading which we refer to as noise.
Alvin, I don’t think we said that ISO was just about how bright or dark the photo was – that was part of what ISO does. If you look further, it is explained in detail that ISO also impacts things like noise and potentially makes images unusable. There is always a trade-off.
Please keep in mind that this article is for beginners. We specifically wanted to avoid such words as “amplification”, “photons”, “signal”, etc, because they are difficult to understand for someone who has no idea what ISO even is.
Interesting explanation, very good for those that are too young to have ever worked with actually film camera. I am from that era and I just equate ISO to film speeds. The faster film had a grainier image quality because of the larger silver halide crystals needed to capture low level light. I experimented once with 15600 speed film – wow, very grainy. In digital cameras your pixel count is sort of equivalent to the silver halide crystals, as you increase your ISO you are grouping pixels together to capture more light in essence resulting in a lower pixel count thus graininess (or pixelation). This is a simplistic view and does not mean that a sensor with less megapixels is more sensitive. You really have to under science to be able to comprehend this hint: look down at the molecular level).
Romas, thank you for your feedback. We have changed this article quite a bit – went from ISO being sensitivity similar to film, to defining it a bit more accurately, but hopefully still in an accessible manner to beginners. But you are right about the very basics – the higher the ISO, the more noise / grain you will see in images. There are also other damages (such as dynamic range), but we decided to exclude more advanced terms from these basics articles for now. We will certainly add them to more advanced articles / material.
It’s important to note that when ISO goes up, dynamic range goes down.
sure, because beginners know what dynamic range is and care about every single bit of EV ;)
Stephen, I asked Spencer to remove references to dynamic range, specifically because beginners have no idea what it is. But you are right, increasing ISO decreases dynamic range dramatically…
Excellent article Nasim. This is one topic that has been beaten to death out on the inter-webs. I’m no expert so I ready/study as much as I can and do my best to try and understand the technical aspects. Below is another article I’ve found that dives deep into the subject. I’m not sure if the link with work on this board. For those that need more to chew on this a bit more just copy and paste or highlight and go!
www.lonelyspeck.com/how-t…and-noise/
Thank you for the link Stephen. It is a great article that goes into a lot more detail about ISO and things like invariance (which we talked about in a separate article before), which are way out of the league for someone who is starting out. We are planning to write a more detailed article on ISO for intermediate / advanced photographers in the future though, because we feel like there is a lot more to talk about, such as sensor size, pixel size, dynamic range, etc.
Think of your sensor as being an array of buckets: An empty bucket is considered a black pixel, a full bucket is considered a white pixel. Changing your ISO means shrinking (higher ISO)/growing (lower ISO) each of these buckets. The “water” filling these buckets is light (think: photons, i.e. light particles). Now it’s easy to understand why upping your ISO will brighten the image: The buckets fill faster and less light is required to top them off, at which point the “water” will overflow (aka “white clipping”). Conversely, with a very low ISO you get large buckets that take a while to fill (“take a while” is referring to shutter speed, of course). So with fast shutter speeds there may be so little water inside some of the buckets that it’s hard to tell them from empty buckets – the pixels related to these buckets are still considered black (“black clipping”). How is that related to noise? Imagine that at the same time you are filling your buckets it is raining. You don’t mind with large buckets, they won’t make a huge difference. Not so at higher ISO with small buckets, now the rain will actually become a problem and it gets worse the smaller the buckets become: The rain starts affecting your image because some buckets randomly fill up faster than others, you begin to see the rain in your pictures. That rain is the noise.
Perfect explanation, hat off! You could add that in the world where a sensor lives, unhappily it always rains! :-)
… and using your paradigm it will be easier to introduce more advanced concepts, such as DR.
Unfortunately, this is an incorrect analogy, albeit a commonly repeated one.
See the article above, under heading: Common ISO Myths and Misconceptions – Is ISO “Sensor Sensitivity”?
ISO has nothing to do with “sensitivity” of the sensor – and it’s misleading to think of ISO as somehow affecting the “size of the buckets in which light is collected”.
In order to better understand the impact of ISO, try this experiment;
– Choose a location where the light is good and of *consistent brightness* – eg. NOT outside beneath clouds on a sunny, windy day.
– Set your camera to P(rogram) mode … in which the camera will automatically select a shutter-speed & aperture to suit the light in the scene.
– Set ISO to 100
– Press the shutter to capture an exposure – and note the shutter-speed and aperture assigned by the camera
– Set ISO to 200
– Press the shutter to capture an exposure – and note the shutter-speed and aperture assigned by the camera
– Set ISO to 400
– Press the shutter to capture an exposure – and note the shutter-speed and aperture assigned by the camera
What you’ll find is that for each doubling of ISO (100 to 200, 200 to 400, etc) there will be a *corresponding reduction* in shutter-speed #. For example, if for ISO=100 the camera assigned a shutter-speed of 1/15 sec – then, at ISO=200 the camera will assign shutter-speed of 1/30 sec – and, at at ISO=400 the camera will assign shutter-speed of 1/60 sec.
This demonstrates the purpose of ISO: At shutter-speed 1/15 seconds we may not be able to hold the camera steady-enough to get a clearly-focused shot – – but we will have a much better chance at 1/60 second. Why? – because 1/60 second is a much shorter time than 1/15 second – and, so, there’s less time for our subject (or the camera) to move and blur the shot.
Hang-on; what? Increasing ISO causes the camera to capture less light ?!! … YES, that’s exactly what happens (due to the shutter being held opened for less time).
So, how does that work for us? – – Because (as the article above explains) “ISO is like a mapping to tell your camera how bright the output photo should be, given a particular input exposure” … How this mapping is actually applied depends on the camera manufacturer’s implementation of ISO: but one way might be to amplify the signal captured by the exposure back to the level determined by the ISO setting – – eg. Changing ISO from 100 to 200 might require amplification of the signal captured by the exposure by a factor of 2, to compensate for the halving of exposure (related to halving of shutter-speed, as determined by doubling of ISO).
Without going into more technical detail, it’s straightforward to say that this is what causes the increase in “photographic noise” as ISO is increased – because, as ISO is increased the camera will *reduce* the exposure time – and so, related to there being less light captured, there is also a higher proportion of random signal (which is a key cause of “noise) – and this is ALL then amplified (or otherwise “mapped”) to the level of brightness determined by the ISO setting.
In other words: The higher the ISO setting the less light is captured (along with a higher proportion of random signal/noise) and therefore the greater the degree of signal “amplification” required to maintain the expected level of brightness … resulting in more visible noise in the image.
Isn’t it just simpler to think of ISO as affecting “bucket sizes”? Why does this matter?
Because;
i) It takes just as much careful thinking to understand the true nature of ISO as it does the myth that it affects the “bucket size of the sensor” … so, why not understand it properly ?!
ii) Depending on your camera, you can take significant advantage of this knowledge … I am happy to elaborate on this potential if anyone cares to ask.
Regards, John – TKA
# Note: For the sake of simplicity I have assumed that only shutter-speed is changed as ISO is increased with the camera in P(rogram) mode – – This may not be true in all cases.
“# Note: For the sake of simplicity I have assumed that only shutter-speed is changed as ISO is increased with the camera in P(rogram) mode – – This may not be true in all cases.”
For the sake of simplicity, why didn’t you set the exposure mode to aperture priority (A) instead of programmed (P)?
” For the sake of simplicity, why didn’t you set the exposure mode to aperture priority (A) instead of programmed (P)? ”
Yes, I did consider that, Pete – but, given the main article is pitched at “beginner level”, I decided to keep my comments as basic as possible.
The same overall logic applies, tho.
Logic? What type of logic is “eg. Changing ISO from 100 to 200 might require amplification of the signal captured by the exposure by a factor of 2, to compensate for the halving of exposure (related to halving of shutter-speed, as determined by doubling of ISO).”?
It is circular reasoning, which is a logical fallacy.
en.m.wikipedia.org/wiki/…_reasoning
Setting a camera to programmed exposure mode (P), then faffing around with its ISO setting in order to obtain the desired shutter speed, is absurd. Teaching this to beginners is way beyond absurd.
A desired shutter speed can be set using either manual exposure mode or shutter-priority automatic exposure mode. Once set, a suitable ISO speed can be set either manually or automatically (auto ISO).
Whenever you use the ISO setting to change the exposure — as per your description — then ISO becomes an inescapable element of the exposure triangle, which is the very thing that you’ve been arguing against via your comments on various articles.
FYI “shutter speed” is a non-hyphenated noun.
I believe you’ve misunderstood my purpose, Pete – I wasn’t attempting to teach beginners anything about actually using their camera.
The experiment I suggested (above) is intended to explain the *impact* of increasing ISO – which, if it’s left to the camera (in one of the auto/semi-auto modes), is actually to *decrease* exposure – – and NOT to make the sensor “more sensitive” (which is a commonly held myth).
John, All you have demonstrated is that increasing the ISO speed setting decreases the exposure when using an automatic exposure mode. NB: Automatic exposure modes simply automate the manual process.
You have failed to explain why the exposure needs to reduce as ISO increases. The photographic image brightness will not change as ISO is changed, in your example, therefore the sensitivity of something to light must be increasing as ISO increases. What is that something?
{{ … increasing the ISO speed setting decreases the exposure when using an automatic exposure mode. }}
Yes, that’s correct – and, as “exposure” is the process of gathering light from the scene, that’s an essential understanding to have.
{{ … the sensitivity of something to light must be increasing as ISO increases. }}
No – that’s a commonly believed, but incorrect, assertion … nothing becomes “more sensitive to light” as ISO increases. As Nasim explains in the main article, above: “ISO is like a mapping to tell your camera how bright the output photo should be, given a particular input exposure.” (See under the heading: Common ISO Myths and Misconceptions … Is ISO “Sensor Sensitivity”?)
In response to your other questions, Pete, I refer you to this excellent article by Spencer Cox: photographylife.com/what-is-exposure … and, in particular, to part 3) ISO (Not Part of Exposure) – wherein Spencer explains; “ISO … isn’t part of your exposure, since it doesn’t actually affect the amount of light that reaches your camera sensor (the definition of exposure). Instead, it merely brightens a photo while [i.e. during the time that] the camera processes whatever image you captured.”
Regards, John-TKA
John,
You told Thorsten Westheider that his analogy was incorrect and you used a logical fallacy in your absurd explanation. An explanation using changes in ISO setting to change the exposure — see comment 36.1 to gain some insight into your error.
1. Changing the ISO setting does change the sensitivity of the sensor because, currently, there are no sensors which are truly ISO invariant.
2. The sensors in the Nikon D3 series, D4 series, and the D5 do indeed increase their sensitivity as ISO is increased above their base ISO. These sensors are far from being ISO invariant.
3. You do not understand the meaning of the technical term “sensitivity”. It has more than one meaning and you’ve failed to specify which of its meanings you have been using.
You have made it obvious that you do not adequately understand the things you write about. I’m simply highlighting your ongoing BS. You are providing a wonderful example of the mess that results when someone uses opinion-based rhetoric instead of the relevant fields of evidence-based science.
Sorry, Pete – but I cannot help you any further … other than by suggesting you actually read the aforementioned articles;
– the one above: photographylife.com/what-…hotography
– and this one: photographylife.com/what-is-exposure
Meanwhile, I’ll leave it to you to have the last word …
Regards, John – TKA
Hi Pete and John,
I think this discussion stems from a misunderstanding. Both of you definitely understand that ISO is not itself a part of exposure, even if the analogy John provided in his earlier comment gave a flawed impression. Meanwhile, there is confusion that stems from using the term “sensitivity” differently, as Pete mentioned. In this article and others on Photography Life, it’s used in the sense that a camera sensor only has one sensitivity, based on the quantum efficiency of the sensor – something that doesn’t change at different ISOs, since it is the ratio of photons hitting a pixel to the number of electrons released.
Hi Spencer,
Thorsten Westheider did not mention “sensor sensitivity” in his analogy. John Morter created a straw man argument[1] of that analogy, for which I’ve taken him to task.
1. en.m.wikipedia.org/wiki/Straw_man
The analogy is correct in that raising the ISO speed setting shrinks the size of the buckets, which explains to beginners “… Now it’s easy to understand why upping your ISO will brighten the image: The buckets fill faster and less light is required to top them off, at which point the ‘water’ will overflow (aka ‘white clipping’).”
The fact that the quantum efficiency and the full well capacity of each sensel in *the detector array* does not change as ISO is increased, is irrelevant, because the *sensor* — which consists of the detector array plus electronic processing (including amplifiers) — cannot output the high electron counts from the sensels at high ISO values. High-performance detectors have a full well capacity many times greater than 16,383 (the maximum count of 14-bit binary).
Assigning the attributes of the detector to the whole sensor and/or the camera is very likely to result in a logical fallacy:
“The fallacy of composition arises when one infers that something is true of the whole from the fact that it is true of some part of the whole (or even of every proper part). For example: ‘This wheel is made of rubber, therefore the vehicle to which it is a part is also made of rubber.’ This is clearly fallacious, because vehicles are often made with a variety of parts, many of which may not be made of rubber.”
[https://en.m.wikipedia.org/wiki/Fallacy_of_composition]
Like it or not, changing the camera’s ISO speed setting changes the sensitivity of the camera according to, at least, the following: Canon, DxOMark, Fuji, Leica, Nikon, Olympus, Panasonic, Pentax (Ricoh), Sony, and Zeiss. NB: The ISO speed setting of a digital camera indicates its selected responsivity to exposure, not its maximum sensitivity / quantum efficiency.
Thanks for the excellent article Nasim.
In some occasions I use the “Lo -1” iso setting when i try to capture moving water (smooth water effect) and a detailed landscape during day time (good light) in combination with (1) a slow shutter speed (2 to 5 seconds ) and (2) a maximum of F11 or F16 (to avoid diffraction). In the manual of my Nikon D7500 i read that iso Lo -1 can being seen as an equivalent of iso 50. If it is really iso 50 why they call it “Lo-1”? Can you explain in a simple way what exactly iso Lo-1 does ?
In the mean time i think to use a gradual ND filter to reduce the light in those situations. I assume that the result will be better than iso Lo-1?
Thanks in advance for your reply
Kind regards, Hedwig
Lo-modes behave like their respective ISOs, meaning you can take correctly exposured pictures as if they actually were ISO 50 and so on. However, they’re not the same, the firmware of your camera simulates these ISOs by overexposing the image and then correcting the overexposure. You will notice that your lights will blow out much easier than with the native ISO. In that sense Lo-modes are a crutch and should only be used if you have no other choice.
As for diffraction, it’s present at any aperture, there’s a compromise to be made between lens errors, depth of field and diffraction. Unless you really need f/16 for DOF or effects (such as sunstars) I’d steer clear of f/16 as diffraction is already quite noticeable at that spot. Find out what the sweet spot of your lens is and stick to that f-stop, only go higher if DOF demands it.
Nasim,
Great to see a simplified article about which keep the simplification as much close as possible to the reality. This is not the case in many other pages. In Digital Photography School for example they wrote a few month ago article with simplification that completely distorted the reality (e.g. increase of detector surface sensitivity), which I think is a always a bad thing to do. I have even been banned from their forum to point this out politely ! Seems that ISO topics is some how emotional !
As I teach the physics of detection, I have quite a bunch of pedagogic materials if interested and you need to go further on that topic.
All the 3 posts about ISO, Aperture & Shutter Speed are great.
Hi Nasim,
‘Tis very “brave” of you to take-on this topic !! … given the many myths and differences of opinion about what it really is and what it really does. No problem, tho, you’ve delivered an excellent explanation of ISO – complete with explanation of what it’s NOT.
Only one thing I’d take issue with; your advice in 7.3) Is Raising ISO Just Like Brightening Your Photo on a Computer? might have been better qualified had you said: “It depends on the camera you’re using” (‘cos some cameras have the benefit of tendency towards ISO-invariance, which makes this eminently possible) … and, “It depends on the dynamic range of the scene” (‘cos, in order to preserve highlights, it may be better to shoot with low/base-ISO and then brighten during RAW-processing – assuming one is using a camera with ISO-invariant tendencies).
Otherwise, tho, another thoroughly good article from the PL team.
“It depends on the dynamic range of the scene” would be incorrect because a scene does not have a dynamic range.
Thanks, Pete … Yes, point taken – I was being a bit loose in my terminology.
I reckon you understand what I mean, tho; … “high contrast scene” would have been better.
Awesome article. The only part I disagree with is 7.2 where you say ISO is not a part of the exposure.
While you are ‘exposing’ the sensor to an amount (aperture) and duration (shutter) of light, the sensor can be influenced by the photographer’s ISO input – and that is directly correlated with the final image. In your example above, shooting a bird at 1/2000 to freeze motion requires a higher ISO to achieve the desired image. Setting the ISO is only an option available during the initial capture of the image, and it is recorded in the EXIF data. You can modify RAW files to an extent, but the Aperture, Shutter, and ISO cannot be changed in post.
Such confusion/disagreement results from the failure to clearly identify the independent variable(s), and the dependent variable(s).
Luminous exposure:
symbol Hv;
SI unit name: lux second;
SI unit symbol: lx·s;
SI dimension symbol: L⁻²·T·J.
Changing the ISO setting does not change the exposure! The required ISO setting depends on the exposure.
Nasim, thank you for the great article. I am not a pro and I’d like to ask you about the example of the birds shot. If you set your camera with a low ISO, 100, shouldn’t the shutter speed be greater than 1/250? because 100 needs less light entering the lens? I hope my question makes sense, I’m sorry if it is an obvious one.
Nope! As you lower the ISO you need *more* light, and hence *longer* exposures (a lesser number in the denominator of the “fraction of a second” with which we measure the shutter speed). See Thorsten Westheider reply above for an excellent “physical paradigm” of how things works.
I find this tutorials so helpful changing the way I view my photography,the way it is explained is is so helpful,thank you.
If ISO upper limit is set to 6400 but it is too dark and you don’t want change Aperture or Shutter, what does the camera do to the image? I know aperture and shutter aren’t modified by the camera (specifically Nikon D850). If this is a rare subject and you want to get the best image as it gets dark, is it better to set your ISO upper limit to the maximum of the camera?
HI, earlier this week I tried to take pictures of my family during a flower event, and the background and the faces would be not as sharp as I want it to be, even after I focused onto the face and changed the Aperture so that the faces stood out. Could you help me out with this?
I am using a Sony A6000 with the lenses that came with it. I just started phtography a few days ago and this helped me out a bunch! Thanks in advance Nasim!
Great article mate. I would try these technique which no one ever told me before. Thanks a lot. Cheers nice work 👌
Great article and your website has really educated me on important aspects of photography.
What lens would you recommend for mainly wildlife photography?
I currently utilize a Canon EOS T6 with a Canon EF 75-300mm f/4-5.6 III Lens that I use for wildlife photography.
My budget would be between $700-$800.
Appreciate and value your guidance.
Thank you and admire your work!
Wow…thank you so much for this elegant explanation. Years of not really undersgtanding when it was really quite simple..Thank you , thank you
Thank you sir, this is very useful for beginners. Do you have any tutorial for video by professional camera.