One of the biggest challenges that many photographers face is yielding sharp photos when hand-holding a camera. Many end up with blurry images without understanding the source of the problem, which is usually camera shake. Unfortunately, camera shake can come from a variety of different sources – from basic improper hand-holding techniques to mirror and shutter-induced vibrations that can be truly challenging and sometimes even impossible to deal with. While I will go over the latter topics in a separate article, I would like to talk about the most common cause of camera shake: lower-than-acceptable shutter speed when hand-holding the camera. I will introduce and explain the reciprocal rule, which can help in greatly increasing the chances of getting sharp photos when you do not have a tripod around.
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Table of Contents
What is Reciprocal Rule?
Due to the fact that we as humans cannot be completely still, particularly when hand-holding an object like a camera, the movements caused by our bodies can cause camera shake and introduce blur to images. The basic premise of the reciprocal rule is that the shutter speed of your camera should be at least the reciprocal of the effective focal length of the lens. If you are confused by what this means, don’t worry – it is really easy to understand once you see it in an example.
Say you are shooting with a zoom lens like the Nikkor 80-400mm f/4.5-5.6G VR (see our in-depth review) on a full-frame camera like the Nikon D750 (in-depth review). All the rule is stating, is that if you are shooting at 80mm, your shutter speed should be set to at least 1/80th of a second, whereas if you zoom in to say 400mm, your shutter speed should be at least 1/400th of a second. Using such fast shutter speeds should prevent blur by camera shake. Why? Because there is a direct correlation between focal length and camera shake – the longer the focal length, the more potential there is for camera shake. If you have a long telephoto zoom lens like the above-mentioned 80-400mm lens, you have probably already noticed how much more shaky and jumpy your viewfinder looks when you are zoomed in to the longest focal length, compared to the shortest one – that’s because camera movement is magnified at longer focal lengths:
Camera Shake Blur is NOT Motion Blur
It is important to point out that blur caused by camera shake is very different than motion blur (where the subject is faster than set shutter speed) – it usually has the whole image blurred, whereas motion blur might only have the subject or a portion of the subject appear blurred, while the rest of the image appears sharp. It is also important to point out that the reciprocal rule only applies when hand-holding a camera – mounting your camera on a stable object like a tripod will not require such fast shutter speeds.
Effective Focal Length
Please note that I used the word “effective focal length” in the definition and gave you an example with a full-frame camera. If you have a camera with a smaller sensor than 35mm / full-fame, (and most entry-level DSLRs and mirrorless cameras have smaller sensors), you first have to compute the effective focal length, also known as “equivalent field of view”, by multiplying the focal length by the crop factor. So if you use the same 80-400mm lens on a Nikon DX camera with a 1.5x crop factor and you are shooting at 400mm, your minimum shutter speed should be at least 1/600th of a second (400 x 1.5 = 600).
Notes and Exceptions
Although it is commonly referred to as “reciprocal rule”, it is not a rule per se – just a guidance for minimum shutter speed to avoid blur caused by camera shake. In reality, how shutter speed affects camera shake depends on a number of different variables, including:
- The efficiency of your hand-holding technique: if you have a poor hand-holding technique, the reciprocal rule might not work for you and you might need to use faster shutter speeds. Gear and lenses vary in size, weight and bulk, so you might need to utilize specialized hand-holding techniques depending on what you are shooting. For example, check out this great article by Tom Stirr on hand-holding techniques for telephoto lenses.
- Camera resolution: whether we like it or not, digital cameras are increasing in resolution and as we have seen in the case of high-resolution cameras like Nikon D810, having more pixels crammed into the same physical space can have a drastic effect on how sharp images turn out at 100% zoom. Higher resolution cameras will show more intolerance to camera shake than their lower resolution counterparts. So if you are dealing with a high resolution camera, you might need to increase your shutter speed to a higher value than what the reciprocal rule suggests.
- Lens quality / sharpness: you might have a high resolution camera, but if it is not matched by a high-performing lens with great sharpness, you will not be able to yield sharp images, no matter how fast your shutter speed is.
- Subject size and distance: photographing a tiny bird from a long distance and wanting to have every feather detail preserved usually requires faster shutter speed than recommended by the reciprocal rule, especially if the subject needs to be tack sharp at 100% zoom (pixel-level).
- Image stabilization: is a major factor and should be explained separately – see below.
Image Stabilization
Reciprocal rule falls apart if your lens or your camera come with image stabilization (also known as “vibration reduction” or “vibration compensation”), because it effectively reduces camera shake by moving internal components of a lens or the sensor of the camera. Since the implementation and the effectiveness of image stabilization depend on a number of factors including manufacturer technology, lens vs in-camera image stabilization, effective use of stabilization technology and other factors, its impact varies greatly from camera to camera and lens to lens. For example, Nikon and Canon both use lens stabilization and usually claim between 2-4 times of compensation potential on lenses, whereas Olympus claims up to 5 times of compensation on its OM-D E-M1 mirrorless camera with 5-axis in-body image stabilization system. That’s a pretty big potential for reducing shutter speed to numbers way below what the reciprocal rule would recommend.
In the above example with the Nikkor 80-400mm f/4.5-5.6G VR, since the lens comes with image stabilization and Nikon claims up to 4 stops of compensation, you could theoretically reduce the recommended shutter speed by reciprocal rule by up to 16 times! So when shooting at 400mm, if your hand-holding technique was perfect and you turned image stabilization on, you could go from 1/400th of a second (reciprocal rule based on a full-frame camera) to 1/25th of second and still be able to capture a sharp image of your subject (provided that your subject does not move at such long shutter speeds and cause motion blur). In such cases, reciprocal rule simply does not apply…
Applying Reciprocal Rule: Auto ISO
Many of the modern digital cameras come with a really neat feature called “Auto ISO“, which allows one to let the camera control camera ISO depending on light conditions. Some Auto ISO implementations are rather simplistic, letting the end-user specify only minimum and maximum ISO and giving little to no control on minimum shutter speed. Others will have more advanced Auto ISO features, allowing to specify not only ISO ceilings, but also what the minimum shutter speed should be before ISO is changed. Nikon and Canon, for example, have one of the best Auto ISO capabilities in their modern DSLRs – in addition to the above, minimum shutter speed can be set to “Auto”, which will automatically set the shutter speed based on the reciprocal rule:
One can even customize this behavior further, by changing the minimum shutter speed relative to the reciprocal rule. For example, on my Nikon D750 I can set the minimum shutter speed to “Auto,” then set the bar once towards “Faster,” which will speed up shutter speed based on the reciprocal rule. So, if I am shooting at say 100mm focal length, the camera will automatically increase ISO once my shutter speed reaches 1/200th of a second. And if I use a stabilized lens and want my camera to have a longer minimum shutter speed, I can move the same bar towards “Slower,” using a longer minimum shutter speed guided by the reciprocal rule.
Nasim, I have found your articles to be extremely helpful!
Re: “photographing a tiny bird from a long distance and wanting to have every feather detail preserved usually requires faster shutter speed than recommended by the reciprocal rule”. Not sure whether anyone has pointed this out, but that advice is totally backwards. For any specific focal length, the closer you are to the subject, any movement of the camera or subject cause the subject to move across more of the field of view during the exposure.
Frank
“how sharp images turn out at 100% zoom”
This. People tend to miss this. The idea that you need minute sharpness at 100% zoom on your computer screen is quite frankly ridiculous most of the time. People need to think more in terms of printed size or actual viewing size. Let’s say I photograph the same item using a 24MP camera and a 50MP camera using the same settings. At 100% zoom the 50MP picture might show more blur compared to the 24MP picture. But zoom out to have the same viewing size and they will be the same.
The sensor size does not influence the reviprocal rule. If camera shake gives a 1% blur on a Fx sensor, it will also be 1% on the center part or on a DX sensor.
Equivalent focal length is only a cropped field of view and has no pptical property as such.
Jacques
Hi. I’ve read a lot of this now and also about DOF and hyperfocal lenghts. All formulas designed for film and now we have DX and also smaller sensors. So I started wondering what is behind the formulas. I’m not so worried about camera shake, I want to figure out shutter speed for moving subjects.
Imagine a D7100 DX camera on a tripod with a 35mm. An athlete running at 20km/h (12,5 mph) passes from left to right 5m in front of the camera and you fire at 1/1000s. What happens if you see the picture at 100%. The speed of that light on the sensor, is 9700 pixels per second. With 1/1000s you get a 10 pixels blur! If you use a D40 (same sensor size, 1/4 pixels) the blur is only 5 pixels. So focal distance, subject distance, subject speed, angle, sensor size and pixel density all have infulence in 100% zoom pixels inspection.
Usually I would pan the camera following the movement, but the legs of the runner are still moving relative to the camera.
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Hi Nasim, I was just wondering what difference the use of a teleconverter would make with regard to this guideline? For example, if I have a 200mm lens and a 2x converter, would I need to set the shutter speed to 1/400 with it attached?
Oddly enough we learned different rule known as reciprocity. Reciprocity refers to the rule that an exposure is the same at say [email protected]/1000th, [email protected]/500th, [email protected]/250th, etc. In the film days this was especially important to know if you did long exposures because films suffer from what’s called reciprocity failure. That’s a phenomenon where film looses its sensitivity in long exposures and that rule breaks down.
I think we learned the rule you refer to as the inverse focal rule. And that only applied to 35mm cameras- it would have made no sense back in the 1980’s with film sizes as diverse as 110 (13x17mm) up to the largest format I ever shot hand held 4×5″ (10x12cm.)
The reciprocal rule is the reciprocal rule – and has always referred to the guidance about shutter speed when hand holding a camera. You may have known it as the ‘inverse focal rule’ but this is mathematically incorrect. I am no mathematician, but reciprocal means to divide by a number e.g. the reciprocal of 500 is 1/500 while the inverse (generally understood to be the additive inverse) is the opposite or negative of a number i.e.the inverse of 500 is -500.
The multiplicative inverse however, does corresponds to the reciprocal! i.e. 1/500.
Then there are reciprocal and inverse trigonometric functions – at which point my schoolboy math gives up and I am lost without trace!
There is an inverse square law, which is a law, (as opposed to a rule or guide), but which has nothing at all to do with camera shake!
Reciprocity failure is not a rule, it is a phenomenon.
It is the way film (and the human eye) behave when exposed to light and varies from film to film (and from person to person).
At ‘average’ values the curve describing the response is more or less linear = twice the amount of light twice the response. At the extremes however, it takes a disproportionately longer exposure to light (or higher intensity) to elicit the same response. Film response is a gamma curve. Digital sensor response is linear.
This is the basis for the gamma curve in photography and explains why we expose differently for digital sensors (ETTR- expose for maximum data) than we did for film (expose for preferred tonality).
The reciprocal rule does not, with respect, only apply to the 35mm format. There are just as many sensor formats today as there were film formats yesterday.
Camera shake is a function of magnification and for a given focal length, magnification is constant. Therefore the reciprocal rule is constant. Only the field of view changes with change of format, not the magnification. To make matters worse, most medium and larger format cameras suffer from horrendous mirror slap so there is an argument for increasing the reciprocal factor to take account of this negative feature.
FYI: I replied to you but needed to include a couple links to Wikipedia and Stackexchange which left my reply “in moderation.” Let me ditch the links and maybe my real comment will be approved eventually.
Here’s what I sent sanitized of links:
Hey Betty,
I think at least some folks see this as I do. As an example this Wikipedia entry on the subject: (search for Reciprocity (photography) on Wikipedia since I guess I can’t put links here)
As for the application to 35mm format in what I know as the inverse shutter speed, format would presumably be a logical measure. Because it would determine angle of view and as such magnification (at least at the same distance.) A super wide lens on 4×5 film like a 75mm (equal to a 24mm in 35mm) would be a moderate telephoto on 35mm or “full frame” digital, and equal to 150mm on 110 film. Obviously the resolving power of a 4×5 film image is immensely greater than that of 110. But all other factors (including resolution) being equal you could get away with a much longer exposure with a big piece of film than a tiny one. That inverse focal rule is truly just a rule of thumb.
Here’s a snippet from a similar discussion I found: “So, I don’t know exactly where it came from, but it’s definitely an idea for 35mm film, and it’s clear that in its early form, it was seen as a general guide, not a law.” (more info here: link removed just look at the search: stack exchange shutter speed focal length rule )
Cheers, -mike
Betty:
There is an additive inverse as you’ve mentioned x and -x;
And there is a multiplicative inverse, also known as the reciprocal as in x and 1/x.
So you’re both correct, just one a little bit more precise than the other.
“The multiplicative inverse however, does corresponds to the reciprocal!”
Isn’t that what I said?
What a delightfully esoteric but irrelevant discussion this has turned out to be.. rather like how many angels can fit on the head of a pin?
Of absolutely no interest to anyone but the protagonists!
The Effective Focal Length chapter is wrong. I think I have told you this before Mansurov.
Consider if you take two images on a d800 and the only thing change is that you take the second one in dx mode. You are saying that the cropped image now magically needed a faster shutter speed. Which of course is wrong since absolutely nothing changed in the physics. Also, since shooting in dx mode is exactly the same as cropping an fx image in the photo editor, you are also indirectly saying that the more you crop an image in editing, the faster shutter speed you should have taken the image with to get the same motion blur as in the uncropped image.
Sensor size doesn’t change either motion blur or ‘reach’.
Normally the whole image or nearly the whole image is used to make the finished photograph (otherwise we’re not optimally using the camera to get the best image quality). The significance of blur depends on the radius of the blur relative to the image dimensions. In most applications, because of limitations in the resolution of the presentation medium, the image is resized to a much smaller pixel dimensions than the original capture. Whether the image will appear soft or not it is usually not necessary to consider the pixel level detail but how easy it is to detect the blur in the final image at the size and resolution it is displayed.
The same is true of depth of field – normally the circle of confusion for DOF calculations is set according to the format size – using larger formats (sensor sizes), the circle of confusion can be larger before the area of the image considered becomes visibly blurry in the final presentation of the image.
Of course, if one is using a small part of the image only (heavy cropping) then the pixel level detail is important and the circle of confusion must be set accordingly, but in that case the image quality will be quite poor, whatever you do. Some don’t care, and that’s their right, of course.
Actually Nasim has said “So if you use the same 80-400mm lens on a Nikon DX camera with a 1.5x crop factor …”,
He did not say ‘changing an FX camera to DX mode’, which, as you rightly point out, will not affect the ‘reciprocal rule’ simply because the pixel spacing (obviously) remains the same.
As Betty pointed out below, the main determining factor of ‘blur’ at the pixel level is due to the spatial distribution of the pixels.
A 24MP FX sensor will have a lower pixel density than will a 24MP DX sensor and thus not exhibit blur to the same extent when viewed at 100%.
Hi Nasim,
I’m very familiar with the reciprocal rule, or rather rule of thumb, from my film days, and I guess it’s the kind of thing that sticks with you and becomes second nature. My first two dSLRs were the Nikon D70 and D300, both DX cameras. I always applied the reciprocal rule without taking the crop factor into consideration, and I had absolutely no problem with this. It actually makes sense to me when I think about it: say I shoot with a 200 mm lens at a shutter speed of 1/200 on my D750. This satisfies the guideline and should thus be OK unless I’ve developed a bad case of the jitters. But consider this: inside my FX frame is a portion that’s the size of a DX frame, and that portion satisfies the requirements as well; after all, the reciprocal rule applies to the whole frame and not just the outer portion!
This reasoning breaks down when looking at far smaller sensors. For example, take the Panasonic Lumix DMC-FZ70. It has a sensor size of 6.17 x 4.55 mm, and its zoom lens goes from 3.58 to 215 (the adjusted equivalent is 20 mm to 1200 mm). I don’t think that the equivalent of 1200 mm can be handheld at 1/200 of a second, so there must be something else going on here. I believe that something is magnification.
I believe the reciprocal rule is perfectly adequate when dealing with DX and FX format cameras, but it’s really just a rule of thumb that has evolved over time based on 35mm film-based cameras and it makes little sens to apply it to very small sensors. Of course, erring on the side of a faster shutter speed is perfectly safe: if the subject is sharp at 1/400, it will also be sharp at 1/600 (disregarding possible depth of field issues arising from having to choose a larger aperture).
Cheers,
Daniel
I’m not sure I understand your logic but if I do (a very big IF), you would apply the rule to the equivalent 35mm focal length. So, in your Lumix excample, you’d have to set the shutter speed to 1/1000 (close enough to 1/1200) of a second or faster.
I’m simply saying that in my experience, you do NOT have to adjust for the cropping factor when shooting DX. In other words, I disagree with Nasim when he writes that your shutter speed has to be adjusted by the cropping factor when shooting DX.
Let’s say I photograph a person with a 100 mm lens and that person ends up being 10 mm tall on my DX camera’s sensor. Well, on my FX camera’s sensor, shooting the same subject with the same lens from the same distance will yield the same result: a subject that’s 10 mm tall on the sensor. There is zero magnification! The only difference is that in the photo taken with the FX sensor, there will be more empty space around the subject. Why should this alter the required shutter speed?
Put differently: do you think I have to adjust the reciprocal rule when I switch my D750 to DX mode? Of course not! The cropping factor does not cause things to be magnified, and magnification is what accentuates the movement of a handheld camera, not the field of view. Nasim says that camera movement is magnified at longer focal lengths. He should have specified “at longer ACTUAL focal lengths” (not adjusted onces) for a lens’ actual focal length is the only thing that determines magnification. For this, the sensor size is totally irrelevant.
Applying the rule to the equivalent 35 mm focal length is Nasim’s idea, not mine. In fact, applying the reciprocal rule to anything other than FX probably doesn’t make much sense anyway; in the case of DX, we’re close enough that one can get away with it (after all, this rule is not at all based on any kind of physical property or law of optics: it’s just something that evolved based on experience of 35 mm format photographers.
Naturally, the reciprocal rule is a generality and won’t apply exactly to everyone but the general theory is sound, if not the exact ratio for each individual. In your hypothetical example, you would have to change the distance from the subject in order to maintain a 10mm sensor coverage and that could (not necessarily “would”) explain your experience.
No! The same lens at the same focal length and at the same subject distance will represent the subject at the same size on ANY sensor. This is the entire basis of my argument: you don’t have to do a thing to obtain the same size. Therefore, you don’t magnify, and thus you don’t accentuate existing camera shake. ITN says you do magnify more when you print, but that’s not what the question is here.
I understand your point but I think there’s more to it than that. Of course, I could be wrong and often am. The fact that “Betty” agrees with you kinda bolsters my POV! ;-)
Now, now, Patrick, you are in danger of hurting a lady’s feelings.
Going back to Daniel’s Lumix FZ70 example, I do not see why the reciprocal rule should change.
We should not get misled by the effective/equivalent focal length as opposed to the actual focal length.
The 215mm zoom still has the focal length of a 215mm lens and the field of view of a 215mm lens, so all the rules regarding magnification for that focal length still apply.
If the real magnification hasn’t changed, then the reciprocal rule for that lens doesn’t need to change either.
The only ‘variable’ that has been introduced is a tiny sensor with a very high pixel density (compared to full frame or even DX) and it is this which may justify the use of a higher reciprocal factor – just as it does for a DX sensor or indeed a pixel dense, full frame sensor such as the D800.
If the reciprocal of the equivalent focal length were the ‘right’ value to use, cameras like the Lumix or Nikon V series would become virtually unusable at their longer focal lengths.
Again using the Lumix example, having to use the reciprocal of the equivalent focal length at 215mm (FL=1215mm) would necessitate a minimum shutter speed of 1/1200sec and we all know that is not the case in practice. It would be plain ridiculous and would result in a barrage of complaints to the manufacturers.
A final thought.
The reciprocal rule is a photographic guide, not a law of optics.
A final, final thought.
If in doubt, use a faster shutter speed!
I gave this thing a whole lot of thought and I think you’re right: “If in doubt, use a faster shutter speed!” My problem is being too slow to see past a few variables. I suck at chess too! :-) Your Lumix example is way too many steps to consider in my limited memory. There must be something to it though; I can’t believe so many people, who do this stuff every day, could be taking somebody else’s word for it. There’s gotta be some basis in fact.
Right now I’m kinda peeved that Nasim hasn’t jumped in to defend what is, after all, his assertion and left me dangling in the wind! ;-)
I think we all suffer from a need to have certainty, a hard and fast rule to follow which will guarantee success. But in this case we are dealing with an empirical rule, not something rooted in scientific fact. The reciprocal rule is just a rule of thumb that has been shown to work from experience for most operators, most of the time, but there are too many variables to be able to calculate a universal formula that will give us the certainty we crave.
Lenses, camera bodies (size,weight and balance) and sensor pixel densities are very variable from one system to another and one format to another – and all these factors have an influence on ‘hand hold-ability’. No doubt there is science behind it, but there is an overriding confounding factor – the operator. The bottom line, as I see it, is that we all shake differently and worse, we all shake differently at different times, and it is this which throws a spanner in the works!
Some photographers just have an inherent ability and/or good technique and get sharp images at very low shutter speeds while others seem incapable of ever producing a sharp image at any shutter speed.
Also, camera shake must be a lot less when one is shooting a calm landscape in a relaxed state after a good night’s sleep than when shooting a critical, fast moving assignment on a tight deadline with a double espresso doing its best to suppress the raging hangover caused by the alcoholic indulgences of the night before!
By the way, if sharpness is the aim, using a higher shutter speed is never going to hurt.
I think it was Jay Meisel who said, “There is no such thing as a shutter speed that is too fast.”
I suspect it is all more art than science.
I guess Jay doesn’t like creamy water flow, etc!? :-)
It doesn’t really affect me because if it matters, I use a tripod. When I can’t use a tripod, I’ll lean my body, arm, or camera against something.
I’m sure it was Bill Fortney who says, ‘there are only two kinds of tripods: ones that work and light ones.’ :-)
No, Mr Maisel was more into documentary, street and advertising photography. A very bold, colourful approach. No creamy, dreamy stuff for him.
I digress, and this may not be true, but I heard it said that in order to nail a shot and/or have duplicates/bracketed options he would hold down the shutter release on his motor driven Nikon F2 and rotate the aperture dial from wide open to minimum aperture and let her rip through a whole 36 frame roll of film.
This is a man who likes certainty and explains why he favoured high shutter speeds!
Notwithstanding, he is one of photography’s greats and to reduce the likelihood of being sued, I unreservedly apologise if the story is apocryphal.
I understand the duplicate/bracket rationale but I would think that method would decrease the likelihood of getting a sharp image. When I have to hand-hold, sometimes I’ll take three shots, at high speed, to increase my chances of getting a sharp image.
Well, maybe take a tip from Jay and fire of 36?
Just kidding.
Betty, I think you hit the nail on the head; with this single comment. Perhaps had Nasim titled his monograph the Reciprocal Guide, much of this discussion would be moot.
All the comments about sensor size, crop factor or megapixels, has no more bearing then the photographic scene itself. As Betty, mentions in another comment when one member suggested the shutter speed should be 1.5 or 2x times the focal length, she commented that what would he do if the early morning light would not allow that. Thomas Stirr seems to be able to hand hold long lenses at slow shutter speeds I would never even give a thought too. He does it and does it well. I’d be on a tripod. As Betty so aptly points out in this discussion, the one single factor to all this is the photographer and what he/she/they are capable of doing in any given situation with any given equipment. It will always be the human factor which will determine how any equipment can be used, especially in photography.
The old computer adage: Garbage In, Garbage Out.
Since I’m often use the same long lenses as Thomas Stirr I must admit that I envy him. My neurological status doesn’t allow my the long shutter speeds he is able to handle. I’ve had to adapt to this (e.g. increase ISO, use a monopod).
But Mike, please don’t call it garbage! There are basic factors that the photographer himself just can’t influence!
By the way, very wise and well explained comment from Betty! Thanks!
Rolf, please forgive the reference as it doesn’t mean what you refer to. What the intent of that phrase is when someone using a computer makes an err, it isn’t the computer but the person using it. With out a doubt, I too cannot shoot long lenses like Mr Stirr. I also have to use a tripod or monopod. The reference was just to the human component of any situation and that cannot be determined in advance. One of my new students is a man with Parkinson’s disorder. Certainly, there is no shutter speed he can use to make a sharp picture. He is always working on a tripod with any lens and cable release. Still, he has eyes that see things most of us will never see and makes fine photographs. .
Normally the composition is dictated by the photographer not the camera or lens. The photographer chooses whatever lens for the camera that they have that gives the desired composition. Thus there is no empty space around the subject (unless it is to be there in the final print); excusing here for small margins of error that are left there to be safe and cropped out in the finishing phase.
Similarly, the print size and viewing distance are dictated by the application, not the camera’s sensor size. Thus the DX image in the sensor plane is magnified by 1.5x more to achieve the same final print size as with making the same photograph using FX. This magnification brings out the camera shake if using borderline or too slow speeds. Thus when using the DX format you may need to compensate and use a faster speed, to achieve the same degree of sharpness in the final print. At the limit of pixel level detail, DX sensors typically have smaller spacing between photosites, so (correctly focused) they are capable of showing finer detail and as a result also smaller scale blur due to camera shake. For this reason faster speeds may also be required to make the most out of the sensor.
Personally I haven’t used 1/FL for ages, it has always been too slow. I normally use 1/(3*FL) or 1/200s (whichever is faster) as the slowest speed limit at which I will attempt hand holding. I think 1/FL is almost guaranteed to result in prohibitative blur, unless a tripod or VR is used. In situations where there is active subject movement if I’m feeling uncritical I might use 1/500s, but if I want to be confident I use 1/1600s or 1/2000s.
You are correct, but you’re redefining the scope of the original discussion. This has nothing to do with composition! If you zoom in or change lenses, then you’re no longer dealing with the situation that Nasim discussed. I’m only talking about on-sensor sharpness. Hypothetical print or display sizes are not relevant to this discussion because they apply equally to what shutter speed you would use in a consideration not involving DX vs FX. Nor is the type of sensor (except for its physical size) relevant: we’re not discussing what speed to use depending on whether we are shooting with a 6 megapixel D70 or a 24 megapixel D7200. This is a theoretical discussion for which you could easily use a hypothetical “perfect” sensor so the discussion is limited to circles of confusion. As for moving subjects, they are out of scope as well, but surely there has to be a difference between photographing a child on a tricycle and an F1 car during a race!
Once again, you make a number of very valid points, but none that have any bearing on the discussion, which is simply this: do you have to increase your shutter speed when you go from FX to DX under identical conditions? Nasir says yes, I say no. You say yes, but you can only make your case by introducing new elements that are not part of the original scenario.
I am with you on this, Daniel – mostly.
Whether FX or DX, it is the actual focal length which determines magnification and hence the effect of camera movement (and hence blurring) at the sensor.
However, we must apply the caveat that this will only be true for sensors with equal pixel density.
So yes, when changing from FX to cropped DX mode on a full frame camera, the 1/focal length rule holds good as the pixel density is not changing. However, when comparing an FX sensor camera with a DX sensor camera differences in pixel density will play a part and so, as DX cameras often have higher pixel densities (and so are more sensitive to camera movement) than their FX counterparts, there is a case to be made for for using a higher factor for DX sensors – and 1.5X is as good a starting point as any other.
So I believe you are right in saying that in principle, taken alone, sensor size is irrelevant, but in practice this may not hold true for DX sensors with higher pixel densities than their FX counterparts.
At the end of the day, this rule is, as you say, something that evolved in days of film as a rule of thumb based on experience and which does not transcribe to the digital domain very comfortably.
I think we all get to know what our own individual limits are for a given camera/lens combination and we soon learn what works and what doesn’t.
Yep, that I can definitely live with, Betty ☺