Is D90 frame rate linked to shutter speed?

J

jimbee

Member
Apologies if this is a dumb question, but I got to wondering today about how, or if, frame rate is linked to shutter speed. Basically, if you are shooting 24p video, does that mean the slowest shutter speed you can choose is 1/24th of a second (or, more realistically, I guess, 1/25th of a second)?

If you wanted the best low light ability, for instance, I would expect a slower shutter speed and a bigger aperture (also to help with shallow depth of field) to be the logical choice. But would it even be possible to shoot 24p video with a shutter speed of, say, 1/15th of a second? (I'm not a D90 owner, just considering it)

Thanks for any enlightenment on frame rate vs. shutter speed,

Jim
 
Nikonslave said:
Short answer: FPS doesn't have anything to do with Shutter speed, sorry
Click to expand...

Well, it kind of does, I don't think you'd be able to shoot with a longer shutter speed than your frame rate, it doesn't make sense.
If you're shooting 24p video, 1/48 is typically a good shutter speed and is referred to as '180° Shutter Angle' since if you have a circular spinning shutter, 180° would expose the frame half of the time. In cinema, you usually don't manipulate the shutter to control exposure, it's more about controlling motion blur. 180° gives a normal amount of motion blur. If you chose 1/24 for 24p video, that would be equivalent to a 360° shutter angle and would be brighter with more motion blur.
 
Last edited:
AndrewGentle said:
Well, it kind of does, I don't think you'd be able to shoot with a longer shutter speed than your frame rate, it doesn't make sense.
Click to expand...
And indeed slow shutter speeds can affect your frame rates. The D90 shoots 24p, so the slowest possible shutter speed would be 1/24. I don't know if the D90 allows slower shutter speeds, but if you went to, for example, 1/12th, you would no longer get 24fps. You'd instead get 12 fps, with each frame duplicated.

At 24p, a new frame is exposed every 1/24 of a second. Therefore you cannot hold the shutter open longer than 1/24th; if you try to, it will result in dropping the frame rate in half and duplicating frames in order to accomodate the longer shutter speed.
 
Barry_Green said:
And indeed slow shutter speeds can affect your frame rates. The D90 shoots 24p, so the slowest possible shutter speed would be 1/24. I don't know if the D90 allows slower shutter speeds, but if you went to, for example, 1/12th, you would no longer get 24fps. You'd instead get 12 fps, with each frame duplicated.

At 24p, a new frame is exposed every 1/24 of a second. Therefore you cannot hold the shutter open longer than 1/24th; if you try to, it will result in dropping the frame rate in half and duplicating frames in order to accomodate the longer shutter speed.
Click to expand...


But if there was a constant shutter speed in D90 movie mode to maintain the 24 fps (i.e. 1/24), wouldn't changing the aperture either underexpose or overexpose the picture? I haven't really tried to make proper movies with my D90, but I played with the movie mode and I could definitely see the change in DOF when I changed the aperture settings (without affecting the exposure).
 
"not slower than 1/24s" means exactly that, it can certainly be faster and that's indeed what happens when you change the aperture. the iso changes too which keeps the shutter speed fairly slow until it's too bright even at the lowest iso, then only the shutter is adjusted resulting in strobing in bright light.
 
You must log in or register to reply here.
Back
Top