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During long exposure capture, do we need to bother about the fps rate? Does it have any relation, or are both are independent of each other?

I searched over the Internet, but did not find any description related to this. I am totally confused about this. I see the FPS term in relation to video, but I doubt it only applies to that.

During capture we talk about only shutter speed, ISO, EV, etc. Doesn't FPS apply as well?

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By definition, FPS means Frames Per Second. It is the number to express frame rate : a number of images displayed/taken in one second.

In Photography, FPS isn't really related to exposure, it is mostly a performance of a camera body. It defines the number of shots a camera can take in 1 second... but not the shutter speed of your settings. For example, the Canon 7D can take approximately 7 images per second (bursts), but you can use a shutter speed of 1/200 seconds (0.005 s) for each image.

The term Long Exposure is used in photography when the photograph chooses a long-duration shutter speed, usually superior to 1 seconds. In this context, talking about FPS isn't very adequate : a shutter speed of 5 seconds yields a FPS of 0.2. That's why most people don't bother talking about FPS when taking long exposure.

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Video is composed of multiple, quick exposures in succession. While a long exposure shot may take as long as video — although what we might consider a short video makes for a quite long single still exposure! — it's just one exposure: the shutter opens, stays that way, and closes when the shot is done.

If you take a 30 minute long exposure, that's one frame at a rate of.... ¹⁄₁₈₀₀th of a frame per second. (Of course, we don't normally say that, because it's kind of silly and not useful at all.)

It is possible to create an effect similar to a long exposure by blending multiple frames, and some cameras can even do that as a special feature. But this is a special case and probably not what you are concerned with.

Still camera specifications do often list FPS, though, separate from video mode. This is for something entirely different from FPS in video — it's for taking a series of separate still photos in a rapid sequence. This is useful when there's a crucial moment that it's tricky or impossible to time, like getting the exact moment of a catch or hit in sports. But here, these are very short exposures, with no relation to long exposure.

  • nitpick quibble with the end of your 1st paragraph:to the uninitiated, that almost sounds like you're saying that FPS is the inverse of exposure time. Of course, that's not true, and not what you're saying. More precisely, a 1 sec exposure limits the fastest possible FPS to 1. – scottbb Aug 11 '16 at 19:26
  • @scottbb Edited... better? I dunno, I could just cut that out entirely. :) – mattdm Aug 11 '16 at 19:35
  • hrm... I guess my pedantic mind would say that the frame rate of a single frame is indeterminate. After all, rate means change in x per change in t. Without delta x, what's delta t? – scottbb Aug 11 '16 at 19:43
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    @scottbb How do you tell how fast you are going when you drive less than a mile? :) – mattdm Aug 11 '16 at 19:45
  • easy. My speed is indeterminate. At least that's the argument I tell the judge when trying to get my speeding ticket thrown out. =) – scottbb Aug 11 '16 at 20:02
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FPS (frames per second) is the frequency rate at which an imaging device displays consecutive images called frames. The term applies equally to film and video cameras, computer graphics, and motion capture systems. Frame rate is usually expressed in frames per second.

(Wikipedia).

So FPS has nothing to do with exposure, long or short. The only thing you might come across FPS in photography is FPS of your camera's screen. But this has no effect on making photos or result.

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