AE "steps/pops"? at

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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).

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Old November 24th, 2008, 09:02 AM   #1
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Join Date: Mar 2007
Location: Fort Collins, CO
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AE "steps/pops"?

I've been shooting my XH-A1 primarily with AGC turned off. My thinking is that it lets me have more control over noise. I also often shoot with the camera in Auto recording mode. I started noticing that when the camera changes the exposure, instead of a smooth transition it changes abruptly and looks poor on tape etc. After some experimentation I found that allowing the camera to do AGC stops this behavior. I have "AE Response" already set to "Low".

Does this make sense? Thoughts? Suggestions?
-- Larry Chapman
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Old November 24th, 2008, 11:14 AM   #2
Join Date: Jan 2008
Location: North Conway, NH
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Originally Posted by Larry Chapman View Post
Does this make sense?
Yeah... actually it does. I shoot motor racing from late afternoon to night from high atop the sky boxes at the track. I've noticed this stair-stepping exposure at night when zooming out from a tight shot. Since the lights at the track are not all that bright I' running wide open at 1/60 with +6db gain.

Although I don't understand the specifics, I have learned that the more the lens is zoomed in, the smaller the maximum iris opening. Since I shoot in AE mode, and some of the extreme tight shots are under-lit, when I zoom out the iris wants to open more. Canon apparently did not design well for this use case.

Just so you know, I used to shoot full manual but AE is much faster than I am, and I experienced the problem with that setting too. I know. That seems to subvert my contention but I would set the iris when not fully zoomed so when going in tight, the iris would open up. No joy either way.

I suspect that auto gain acts as a bit of an exposure "shock absorber", if you follow my analogy. Auto gain can react more quickly than the iris so it compensates as the iris changes. Since I shoot in the dark, your remedy will not work for me because I'd end up with more grain than a dairy farmer.
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