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Is it possible to set exposure time greater than 30 seconds while using interval shooting? I know we could set the interval, number of intervals and number of shoots I each interval but i can't find anything to set the length of exposure. Please help!

mattdm
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Vamsi
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1 Answers1

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No, the shutter will not go longer than 30 seconds unless you use Bulb shutter mode with an external timer that allows longer than 30 seconds. Then in Bulb mode, the timer can control it. There are several external such timers available for $20 to $25, search Amazon for Interval Timer D750.

If using the camera interval timer, you just set whatever shutter speed the camera can do, up to 30 seconds. Be aware that 30 seconds is actually 32 seconds, so the interval will need to be 33 seconds.

To avoid that causing a stir from readers, I should add that camera shutters MUST have speeds in the sequence of 1, 2, 4, 8, 16, 32 seconds, each exactly 2x longer, so that each stop is exactly 1 EV. Same for fractional speeds, the actual times must be 1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256, 1/512, 1/1024 seconds, etc. This is simply how digital works, each shutter speed is exactly 2x. Has to be that way. The marked numbers are simply nominal values, for the convenience of humans.

WayneF
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    Not all camera makers follow the full stop sequence with regard to shutter times longer than one second. Some actually time the 15 and 30 second exposures at 15 and 30 seconds. The difference between 30 and 32 seconds is only about 6% or less than 1/10 stop. – Michael C Mar 13 '18 at 04:50
  • It is about impossible to imagine that a camera with a digital timer (with a cpu chip) does not do the 2x steps required for EV. – WayneF Mar 13 '18 at 15:25
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    Not as impossible as it is to explain to too many camera owners that their "expensive" entry level camera that they spent their "hard earned cash" on isn't defective because it requires 32 seconds to take a 30 second photograph. – Michael C Mar 13 '18 at 15:31
  • If that could possibly be true, those are surely camera choices to avoid buying, if they cannot even get the first basics right. :) – WayneF Mar 13 '18 at 15:45
  • Thanks for your help @WayneF. I went too optimistic over D750 capabilities. – Vamsi Mar 14 '18 at 03:16
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    @WayneF Film speeds, shutter times, and apertures have never been anywhere near the precision of 1/10 stop for the vast majority of the history of photography. Neither has the output of most artificial light sources, much less natural ones. If you want lab grade equipment, buy lab grade equipment. You might be surprised at how much the actual shutter times vary from the ideal of your Nikons. – Michael C Mar 14 '18 at 04:27
  • This is simply how digital works, each shutter speed is exactly 2x. Has to be that way. As an electronics engineer who specialized in digital circuits, I can assure you that it does not have to be that way. I see that my D600 indeed takes 32s for a 30s shot; an abomination that ruined my astrophotography session last night! (the explanation of why it happened would take too long). Funny how I can set it to 25 seconds, and it indeed does exactly 25 seconds ... same for 20s (it does exactly 20s) 30 seconds? not so much exactly... for 15s, it actually does 16 (following the 2x pattern) – Cal-linux Sep 21 '20 at 17:35
  • Yes, it is how digital works. The goal is that 15 sec takes 2^4 = 16 secs, and 30 sec takes 2^5 = 32 secs. And technically, 20 sec also takes 2^4.333 = 20.16 secs, and 25 sec takes 2^4.667 = 25.40 secs. :) – WayneF Sep 21 '20 at 17:46
  • What you're describing is an (arbitrary) choice of geometric progression of shutter speeds (a reasonable choice, yes), and not "the way it works". A digital circuit, let alone a microprocessor, as surely is what's inside digital cameras, can do essentially any shutter speed (within practical technological limitations). A digital camera could do 21 seconds, if the designers decided that they want to do that; they could do 3.1416 seconds if they were trying to be cute. With traditional digital circuits, dividing frequencies by 2 is easy; but dividing by any number > 2 is possible. – Cal-linux Sep 21 '20 at 18:05
  • You are actually arguing it? Yes, any number may be possible, but the values are NOT arbitrary in cameras, where only a few numbers are of interest (the powers of 2). The overwhelming concept of exposure of camera settings is that 1 EV is 2x exposure. Third and half stops are also of interest (and tenths of EV to some meters). Your difference in 30 and 32 sec is only 0.093 EV. 16 sec is 2^4, and 20 sec (nominal) is 2^(4 1/3), and 25 sec (nominal) is 2^(4 2/3), etc. If you are able to measure your 25 sec more accurately, you'll see. Nominal 13 sec = 12.7 sec MUST be exactly 1 EV less than 25. – WayneF Sep 21 '20 at 18:35
  • Guessing your trouble with 30 seconds was when using the interval timer, you set 31 seconds intervals assuming it would handle 30 seconds. But 31 will NOT handle the actual 32, so the interval should have been 33 seconds, and then that works fine. – WayneF Sep 21 '20 at 18:51
  • "trouble with 30 s was when using the interval timer". Correct; I used to have the timer at every 35 seconds; then, I got a faster SD card that stores a picture in about 1/3 or 1/2 second, so I set it to 31. Then I notice that it takes about 30 sec after the end to start the next one, and I was puzzled; but it had been a while since I had used the interval timer, so I figured, "oh, it must be that it is the time after the end of each exposure", so I set the timer to 1 second; of course, after just a few minutes, it was done with the "240 x 30s" exposures )8‒[ – Cal-linux Sep 21 '20 at 19:36
  • I don't disagree with the choice of 2x progression; what I find an abomination is that something says 30s when it actually is 32s. I mean, how hard is that: if something is 32 s, how hard can it be to say that it is 32 s????? (rounding to integer, I think is fine; e.g., saying 25 when it is 25.4, ok, I find that reasonable) – Cal-linux Sep 21 '20 at 19:45
  • Well, any and all dials (such as Sekonic light meters) say 30 but implement 32. So numbering one 32 would likely confuse many. Just how it is, from the historic past. The 30 is a nominal number that we are used to, like 1/1000 is actually 1/1024. But it does seem like Nikon could mention 32 seconds in the manual section for the interval timer, since many users don't realize. Manual says the interval must longer, and I think that works for 13 & 25, but that's no defense for the 30. :) It's a detail not of much interest in general, but it is important to the interval timer. – WayneF Sep 21 '20 at 20:16
  • Agreed. Perhaps it's just a matter that I'm bitter because I fell for it, hitting the only "rough corner" that there is to it. Of course, now that I know it, I just know it, and the thing will never again be a problem for me (hmmm, famous last words? :‒) ). But it's still a peeve; as you point out, it should be mentioned / emphasized in the User Guide's Interval Timer section, at least. – Cal-linux Sep 21 '20 at 22:26