Of Actual shutter speeds and interval timers...

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Lettermanian Senior Member • Posts: 1,868
Of Actual shutter speeds and interval timers...

Warning, long post

I have been a hobbyist photographer for many years, but never delving too deep into technical matters (though am fascinated by posts that do tackle these things). Several months ago I switched from Fuji to Nikon Z, but have still followed Fuji’s progress and occasionally step into this forum. On a side note, I am contemplating returning to Fuji for the ooc colours and overall experience, but that is not the focus of this post). One of the reasons I switched to Nikon was for their more advanced in-camera interval timers and timelapse video features.

However, lately I have learned something about shutter speeds and interval timers that I didn’t know before, and thought it worthwhile to open a discussion about it, and more specifically how Fuji’s implementation actually works. If you know this already or see it as basic knowledge, you can say “Well, DUUHH!” to me and move on  I’m hoping those who know much more about this subject can chime in and confirm or clarify the following statement: Actual shutter speeds are progressively different from marked or set shutter speeds, and this can affect certain types of shooting.

When I read this article on actual shutter speeds by Nikon ambassador John Shaw, it made perfect sense: that shutter speeds increase in stop increments, or “doubles” and “halves”. For example, shutter speeds increase in speed on your dial like so: 1, ½, ¼, 1/8, 1/15, 1/30, etc. BUT, the camera follows the increment rule, so the speeds are actually 1, ½, ¼, 1/8, 1/16, 1/32,1/64, etc. It also goes the other way when slowing down the shutter speed: 1 sec, 2, 4, 8, 16, 32, 64, etc, not 15, 30, 60 etc. A question I have at this point is when we set the shutter speed through the menu, i.e. 20 seconds, is that then indeed a 20-second shutter duration, or is it slightly more?

One can see how certain types of photography might be affected, such as interval timer photography. Fuji’s in-camera interval timer is quite basic, but newer cameras have an Exposure Smoothing feature, which is supposed to automatically change exposure parameters based on changing lighting conditions (i.e. holy grail dark-to-light sunrises or light-to-dark sunsets). What happens if your interval is too short for the actual shutter speeds the camera is using vs what you have set manually? You’d probably have skipped frames or an interval shooting session that doesn’t shoot the expected amount of exposures. Nikon’s interval works from the start of one exposure to the start of the next, so if one has set a 30-second shutter speed, they need to set at least a 31-second interval to the start of the next shot. The problem is that 30 seconds is actually 32 seconds, so if Interval Priority is turned on, there will be missed frames and likely a failed interval session. To my knowledge Fuji doesn’t have an Interval Priority On/Off feature in-camera, it’s basically always going to shoot at the interval, unless of course it can't

At the moment I don’t have a Fuji camera to test this on, but I would appreciate clarification on how Fuji defines intervals: is it the time from the closing of the shutter in one frame to the opening of the shutter for the next frame, or is it like Nikon’s? Whatever the case, I think it’s important to know exactly how the intervals and shutter speeds work if one wants to pursue interval and timelapse shooting without getting perplexed or frustrated by how the camera actually implements these features.

Sorry for the long post but hopefully it will be helpful to someone. 

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