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I'm being forced to work with a shutter that jitters (e.g., a 1/60 shutter could be anywhere between 1/59 and 1/61). I can't change the hardware, so please don't suggest that. I would if I could.

Say I need to take multiple photos of the same scene with the same aperture, ISO, and this jittery shutter. What is the fastest shutter I can use before the jitter will produce a noticeable difference in brightness? No, I can't post-process.

Should I limit the jitter to 1% of total exposure? 5%? 10%? When will people start to perceive the difference? It's not so easy to test this directly because I can't capture an image and precisely measure the actual exposure.

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I'm not sure what you mean by jitter. I'll upvote you so you should be able to post pictures soon. –  Paul Cezanne May 21 '13 at 12:34
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@PaulCezanne I think that he means random shot-to-shot variation in actual physical shutter travel time from the nominal, ideal time. I've heard this term used before in this sense but can't find a reference to it right now. –  mattdm May 21 '13 at 12:52
2  
Why are you not able to do post production? If you could do even very minimal post and shoot raw then you could adjust the exposure after shooting as long as it isn't sliding so far out that it exceeds the buffer that the extra dynamic range of RAW gives you. –  AJ Henderson May 21 '13 at 15:00
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Jitter is a common term in electrical engineering to refer to variation in the period of a wave. –  Phil May 21 '13 at 15:07
    
Even not shooting RAW you should be able to adjust exposure +/- 1 EV, obviously not as losslessly. –  mattdm May 21 '13 at 16:07

2 Answers 2

Because the exposure factors of ISO, shutter speed, and aperture are interchangeable in terms of final exposure, you can experiment with this yourself by loading a sample image into a photo processing application like Darktable and playing with the Exposure slider.

The bad news is that the human eye is really good at this, at least when the images are shown in sequence. I can easily tell a difference of about 0.05 EV, and even smaller changes are apparent if I'm paying attention.

On the other hand, were the photos to be displayed across the room from each other, I bet most non-photographers wouldn't notice a difference of up to half EV.

(Note that 0.05EV is not a percentage, since the EV scale is logarithmic; it's something like 3.5%. And half an EV is 41%. I think you might be able to get away with 1%, but it'll depend on a number of factors; it's probably best to decide for yourself what's acceptable.)

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Side by side, the eye is extremely good at detecting changes in brightness, but that ability goes down considerably if the images are separated. We're very good at detecting changes from one point to a point next to it (contrast), but much less able to do absolute measurement.

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The question asker explicitly notes that he can't post process the images (for some reason). This makes the first part of your answer not applicable to this question. –  Bart Arondson May 21 '13 at 14:53
    
@BartArondson - oops, good call. I missed that part. I moved that portion to a comment on the original question. –  AJ Henderson May 21 '13 at 14:58

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