What's the shutter doing in video mode?

[thomearl]

Not sure if this is the correct forum, but I don't know much about video or moving pictures, so maybe someone here can enlighten me. Just trying to wrap my head around this new tool we have. In video mode on my 5D II, what exactly is the shutter doing?

And I've read that if you use a shutter higher than 1/125 on moving subjects, you may get an undesirable strobe motion type effect. Are there other effects caused by other shutter speeds that I should avoid?

 

[GtoJon]

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[thomearl]

Really? Then why is there the option to change the shutter speed???

 

[Ken Phillips]

... in video mode. That's a potential problem because the CMOS chips in Canon DSLR's don't capture a frame at a time. It's a more continuous top-to-bottom striping, which means that the top and bottom of each frame has occured at a different time! Known as a "rolling shutter", this can make for some interesting effects.
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[Scott Larson]

Really? Then why is there the option to change the shutter speed???

The same reason you can change the "shutter speed" in your cell phone camera.

 

[bronxbombers]

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[thomearl]

Ok, so I get it now. Thanks for the explanation Ken. So what about my second question? If the chip is acting as the shutter, then are there speeds that I need to be concerned about?

 

[Scott Larson]

If you use too slow of a shutter speed, motion will look more blurry and unnatural. You can try shooting some traffic with a 1/30 shutter speed to see what this looks like.

There are also some types of lighting that will cause slight flicker with faster shutter speeds although 1/125 is probably not fast enough to cause anything too noticeable. There are also things like television screens and LED displays that cycle so they'll flicker if the shutter speed is faster than their cycle speed. You'll be able to see these on the screen.

 

[Ken Phillips]

One is a slightly stilted motion caused by fast shutter speeds (negating the bit of motion blur that really helps smooth things out) AND the rolling shutter effect. Also, certain speeds may make rotating objects appear to stop, or turn backwards.
Most of these things will NOT affect your day to day shooting.
KP
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[liquidstone]

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