ISO is one of the three pillars of photography (the other two being shutter speed and aperture), and it has a major effect on your images. How does camera ISO affect your images? In this article, we will introduce ISO for beginners and explain how to use it effectively for the best possible results.
Table of Contents
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 can help you capture images in darker 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).
What is the Meaning of ISO?
The acronym ISO stands for “International Organization for Standardization”. However, camera ISO does not directly refer to the organization that creates various technology and product standards. Ever since two film standards called ASA and DIN were combined into ISO standards in 1974 (later revised for both film and digital photography), they were referred to as one word “ISO” from that point on. Although ISO initially defined only film sensitivity, it was later adopted by digital camera manufacturers with the purpose of maintaining similar brightness levels as film.
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 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 Camera 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.
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.
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.
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!
ISO increases or decreases the brightness of a photograph, but also affects both grain / noise levels and dynamic range. At the lowest (base) ISO setting, your images will have the least amount of noise and the highest dynamic range, giving you the most flexibility in post-processing. As ISO is increased, noise levels increase and dynamic range typically decreases as well.
When shooting in low-light conditions, your shutter speed will typically decrease, resulting in camera shake or motion blur. To avoid such issues, you should increase ISO setting to a higher value, such as ISO 1600. Depending on your aperture and light conditions, you might need to increase ISO even more.
When photographing landscapes, you should use a tripod and set your ISO to your camera’s base ISO, which is typically 100.
Conclusion
If you have any questions, comments or feedback, please post them in the comments section below.
While the article is much better than most ISO or exposure related articles in the web it still floats the incorrect idea that raising ISO increases noise (or grain). First, in digital there is no grain, it’s a property of film and doesn’t even provide a good analogy. Second and more problematic issue is the idea of noise going up with ISO – this is simply false and usually the exact opposite of the truth. If you use an autoexposure program (anything but M mode), then increasing the ISO indeed appears to increase the amount of noise, but it’s not the raising of ISO, but the reduction of exposure which causes the increase in noise levels. This is trivial to prove: take two shots (in raw), same exposure settings, one at ISO 100, the other at ISO 3200 or something like that and display the processed output at the same lightness level – with almost all the cameras the ISO 3200 image is cleaner, even much cleaner than the low ISO image. What causes the noise is lack of light, not increase in ISO.
Absolutely correct! I remember reading this somewhere else a few years ago. I also noticed it happen consistently with my photography. Especially with images that I take inside my home, where light levels are inconsistent. If I take a photo with a high ISO for one of my kids, but this photo happens to be taken where the ambient light of the sun coming through the window lights his face – or part of it – sufficiently, the image comes out clean. Even at ISO 3200 on the APSC Z50. If I take the same photo further away from the window, using the same ISO, the resulting image comes out noisier. It’s all about the light.
A very thorough and absorbing explanation of this topic. However, as per your opening paragraph, please, please stop propounding the myth that ISO is an acronym. It is not. If it were then it would be I O S. It is pronounced “eyeso” and not I S O and is from a greek word meaning “equal”. It grates on me when I hear so-called professional photographers saying I S O.
Anyway, thanks again for an excellent article on the subject of EYESO.
ISO Is from the organization “International Standards Organization”, who developed the film sensitivity standard. (Originally, called ASA, the American Standards Association developed the first standard for celluloid film.) ISO is just a determination of how many electrons need strike a pixel before a reading of white light is registered. I.E.:ISO 100 (the most “sensitive”) = 100 photons, ISO 1000 = 1000 photons. (The former is just an example, and the actual amount of light is dependent on the size of the pixel, the camera manufacturer, etc. Typical values for modern dSLRs are several tens of thousands of electrons per pixel.)
> ISO Is from the organization “International Standards Organization”, who developed the film sensitivity standard.
It really isn’t, because that’s not their name. Please read: www.iso.org/about-us.html
In particular the “IT’S ALL IN THE NAME” infobox.
International Standards Organization makes sense in English, but in other languages it would come out as SOI. So it appears that the standards organization has disavowed that explanation in favor of the (rather suspect) ‘Greek’ one.
Nonetheless, I feel that it is confusing (especially now with ‘auto ISO’ features) to new photographers unless they realize that the ISO rating was a kludge to try to make it comparable to film photography. Maybe ok for us old times, but really makes no sense at all to people in the digital era.
To the newbies, I suggest, don’t sweat it. It should have been named something like amplifier gain. (But turning it up to 11 is not a great idea)
“International Standards Organization …”
No, it isn’t. Here’s the description from
www.iso.org/about-us.html
QUOTE [Retrieved 2020-04-12]
IT’S ALL IN THE NAME
Because ‘International Organization for Standardization’ would have different acronyms in different languages (IOS in English, OIN in French for Organisation internationale de normalisation), our founders decided to give it the short form ISO. ISO is derived from the Greek ‘isos’, meaning equal. Whatever the country, whatever the language, we are always ISO.
END of QUOTE
Yes, it was an unfortunate evolution from acronym to noun, with a slight saving grace in appearing similar in sound to the Greek word for “equal”. However, the explanation of its mechanics became clearest when you mentioned that it should have been called something like “amplifier gain”, if indeed the “sensitivity” is actually accomplished through voltage. In any case, this is the explanation of the process I most prefer. Thanks for the lightbulb moment.
The amplifier gain analogy is inverse in the case of ISO with the smaller signal (quick shutter and/or small aperture) requiring more amplification to get the same output. Amplifiers produce hiss (noise or entropy) all the time (some more than others). When the gain is down it becomes noticable. since it is no longer drowned out by the amplifier signal, in other words, a low signal to noise (s/n) ratio. Too much amplification of the source signal will result in sine wave clipping, think over exposed.
Amplifiers can be oversaturated at the input too since it is common to stage amplifiers. When doing this usually the preamps are oversized and would overdrive subsequent stages but the overage is divided off therefore assuring subsequent stages have a suitably strong, clean (high s/n ratio) signal as well as not overdriving (clipping). Boosting a weak preamp signal (low s/n ratio) also boosts a lot of hiss.
Light and sound are both waves and in both cases, at the most basic level, the electronics processing the signals are using amplifiers, voltage dividers and filters (inductors and capacitors). One could draw obvious correlations that would lead to the conclusion that a higher ISO would have less noise (by ratio) and less headroom (dynamic range). One could also conclude that this is the reason noise in pictures becomes less and less apparent as the colors become lighter (whiter areas have a higher s/n ratio). An image can’t get any whiter than white.
Communication require interpretation. When people ask where ISO comes from or what it means, most have the basic sense to recognize that full capitalization of the name would be associated with an origin as an acronym, even if it is not an acronym now. People with typical social and communication skills understand that reality. That is one reason the typical answer to the question would include the acronym from which ISO originated. If your atypical mental abilities lead you to feeling grated on, that is possibly because you lack a normative understanding of people and communications more so than anything else.
Consider the question, “What does IBM stand for?” If you just said, “It is the name of the company, that’s all. It has no underlying meaning,”, your answer would be incomplete according to normative interpretations of the question. Most people know what that question means. A complete answer would be, “Originally, it stood for International Business Machines. However, the company was concerned that the name induced limited customer perceptions of the breadth of the company products and services. So, the company decided the name IBM would not be an acronym. Instead, IBM would just have its own stand-alone meaning as a name.
Also, you should understand there is literally NO organization that authoritatively controls how people use the English language. In old times, acronyms included periods. These days, it is quite rare to see use of the period in all but highly formalized communication. For example, USA is the extremely common way for people to refer to the United States of America. USA *is* an acronym. People just don’t use periods. If you don’t think, just go search for “USA”. Look at public signs and read news articles referring to the USA. The days of acronyms with periods are basically over. The people have decided. How a language is used determines the rules, and so acronyms with periods have become anachronistic.
QUOTE
ISO [proper noun]: International Organization for Standardization.
Origin
From Greek isos ‘equal’; the term is often erroneously thought to be an abbreviation.
www.lexico.com/definition/iso
END of QUOTE
NB: Both the name ISO and the ISO logo are registered trademarks and their use is restricted.
“USA” is not an acronym; it is an initialism.
QUOTE
acronym [noun]: An abbreviation formed from the initial letters of other words and pronounced as a word (e.g. ASCII, NASA).
initialism [noun]: An abbreviation consisting of initial letters pronounced separately (e.g. BBC).
END of QUOTE [from Lexico, as above]
“When people ask where ISO comes from or what it means, most have the basic sense to recognize that full capitalization of the name would be associated with an origin as an acronym, even if it is not an acronym now. People with typical social and communication skills understand that reality. That is one reason the typical answer to the question would include the acronym from which ISO originated.”
It has *never* been an acronym.
@Peter Keddie- You are not correct. ISO is the international standards body that has codified many things including black & white film (ISO 6), Currency Codes (ISO 4217), Quality Management Systems (ISO 9000 series), archival data systems (ISO 14721), date & time representation (ISO 8601), etc. I was the Editor of ISO 19128 Web Map Service standard.
Why do my photos taken with Nikon d850 in Aperture mode get darker as I lower the f/stop?
One thing I learned was that ISO is not part of exposure. Shutter Speed and Aperture brighten your photo by physically capturing more light
“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.”
If this is true, and it’s purely a digital post-processing procedure rather than an analog voltage gain on the sensor, then why is there not the option to save multiple ISO versions of the photo when you take the photo?
There is in my camera — Fuji XT-2
Agree, something doesn’t add up. I don’t see how one could say:
“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.”
While also saying:
“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!”
If there isn’t a difference in information captured, why would a computer under-perform a camera?
Yeah, it actually does change the sensitivity. Digital sensors work by translating the detected light into an electrical charge that’s sent to the digital coverter layer of the image sensor. The ISO setting determines the value of that electrical charge (higher ISO defines a higher charge). The higher settings output less accurately, which is why you get noise. Noise and grain are not interchangable terms, as grain only happens on actual film. Grain is inaccurate luminance, while Noise is both luminance and color.
The ISO setting absolutely does not “define” the electrical output of the sensor, it’s just that it can be implemented that way. And at any rate, that’s not what causes noise. Most of the noise that you see in high ISO images is simply a consequence of shooting with little light, as light is noisy itself. If anything, amplifying the signal more means that the electronic noise that is added later (“downstream noise”, see photographylife.com/iso-i…-explained ) is of lesser importance, which is why input-referred read noise tends to *decrease* at higher ISO settings: www.photonstophotos.net/Chart…rk%20II_14
Great article mate. I would try these technique which no one ever told me before. Thanks a lot. Cheers nice work ?
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!
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?
I find this tutorials so helpful changing the way I view my photography,the way it is explained is is so helpful,thank you.
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.