FPS/Shutter/Aperture for video

K

Kastro

Well-known member
Hello all,

I've been misunderstanding my device(t2i) or in general, misunderstanding FPS/Shutter speed as it relates to video capturing.

When I set the t2i to 720/60 I noticed the shutter speed drop to 60 and not allow me to lower it, but did allow me to raise it. I know when shooting photos, the higher the shutter, the better to capture an image that is moving rapidly. I thought that when in video mode, it essentially became the FPS since it changed based on the settings that I chose and allowed me to make adjustments. Which to me, told me 'you can bump this sombitch up to 120 and have 120fps of data to play with'


My question is:
Why when I have 1080/24, I can adjust the shutter to anything higher and it affects my video (darkens it), if its not being used? Shouldn't it be controlled via the aperture in regards to letting in the light? Why allow me to change the shutter speed if I'm recording video?

There is something fundamental that I'm missing and would greatly appreciate it if someone could educate me, or point me in the right direction.
 
Shutter speed is how long the "shutter" is open for. As in, how long each frame is sampled for. as in not adding more frames, but adding or removing TIME from the EXPOSURE.
 
if you're shooting in 720/60, you'll want your shutter at 1/125 or above
If you're shooting 1080/30, you'll want your shutter at 1/60 or above
 
Thus, your shutter can not be open more than all the time, so your shutter can't be lower than 1/30 in 24P and 30P and 1/60 in 60P.

Generally you want to look at shooting at twice the framerate, thus giving you 1/50 for 24P, 1/60 for 30P, and 1/100 or 1/120 for 60P
 
You need to read up on cameras in general, and learn what each feature does and how to use it to your advantage. But here are the basics:

Frame rate is a video/motion film item. Pretty simple: how many frames are captured each second? In film terms, how many individual frames of film are exposed each second?

Aperture (f stop) has to do with the iris, and how much light it lets in. The lower the aperture number, the wider open the iris is and the more light is let in. Also, the lower the number (wider the aperture), the shallower the focal plane. Want lots of stuff in focus in front of and behind your subject? Use a small aperture (14, 22, etc.). Larger apertures like 3.0, 2.8, 1.8, etc., are used to blur most of the foreground/background.

Shutter speed has to do with how long each frame is exposed. This also impacts how much light reaches the sensor (or, traditionally, film) for each exposed image (or frame). Just like taking still photography, you have to create a balance between aperture and shutter speed to get your desired image. The reason you cannot set a shutter speed lower than the frame rate is because that defies the laws of physics. You cannot expose a frame for 1/20 of a second when the frame itself is 1/30 of a second. BUT, you can expose that frame for a shorter period of time.

And last, ISO (in traditional video cameras, you have gain settings) helps control exposure by making the sensor more or less reactive to light. In DSLR cameras, ISO settings mimic film-speed emulsions for different levels of light. The lower the ISO, the more light the camera needs to expose properly. 100-speed film is used for portraiture, landscapes, and other stuff where minimal grain and maximum detail are desired (i.e. subjects that can use long exposure times, or have tons of available light). 400-speed is all around indoor-with-flash and outdoor-on-a-cloudy day film. 800-speed, and often 1600-speed, may be used for fast-action shooting such as sports, where a fast shutter speed means the film needs to react better to lower amounts of light.

There's a caveat with DSLR for HD video, however: unless you are shooting in daylight without any added lighting, keep your shutter speed at 1/60 for NTSC, even if you are shooting a 24fps. This has to do with the electrical system (in Europe/PAL country, stay at 1/50). Shooting under synthetic lighting at a frame rate other than 1/60 may result in a pulsating color shift or other nasty artifacts.
 
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@C2V, i'm familiar in the settings as it relates to photography, but when it comes to DSLR video i was a bit confused and thought that it changed the shutter speed function to control fps. At least that was my initial perception upon first time shooting video with DSLR. I guess thats what I get for thinking to far ahead w/ technology eh?

Bear in mind that I'm still pretty new to video in general (as it seems a rash of people are getting into video too). Thanks for all the advice as it indeed help clarify usage whilst shooting video.
:D
 
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