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Canon GL Series DV Camcorders
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Old December 6th, 2003, 03:55 PM   #1
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Exposure doesn't matter ;)

Hello. This is my first post, love my new GL2, etc. etc. ;)

Did some test shots of the snowy weather today. Since I'm all about manual mode, I did many test shots at different exposures. I started with the level that the GL2 thought was appropriate, and tried 6 stops above and below.

Common sense tells me that 'auto' mode will give you an underexposed picture looking at snow. This is because the camera tries to make the overall picture neutral (which works in most situations), but snow is white, not gray.

The best look appeared when shot with several steps extra exposure, as anticipated. Taking everything into premiere, I found the Levels command would make it look even better (typical). I would reset the white point and black point, to give the video more contrast and definition.

But here’s the kicker: I could make any shot look almost the same with levels. Does it really make any difference what the exposure is if you are just going to readjust later?

I think the idea is to obtain the best dynamic range one can with the camera. That way the most information is copied to tape. But each step looked like it just *shifted* the dynamic range up or down the luminosity scale. So may the picture be underexposed, overexposed, or balanced, it ends up the same.

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Brian Klug
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Old December 6th, 2003, 04:01 PM   #2
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Underexposing will cause a lose of detail and will lead to visual banding (posterization). Read my post about Expose to the Right at the end of this thread.
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Old December 6th, 2003, 05:31 PM   #3
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wow

Quote:
Expose as hot as possible (over expose) without clipping the signal.
Jeff,

That was precisely what I was looking for. Thank you so much!

Brian
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Old December 6th, 2003, 06:00 PM   #4
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You'll still need to post process. Your shadows will be too light if you don't.
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Old December 6th, 2003, 09:35 PM   #5
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where in MD are you from brian?
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Old December 6th, 2003, 11:14 PM   #6
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Jeff, wish I had come across that exposure post a long time ago. Although I fully understand binary and your post makes perfect sense, I never really thought about the huge impact it has.

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Old December 7th, 2003, 09:26 AM   #7
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I have never filmed a snow event so I will ask this question? Canon gave the user an snow exposure mode in the menu, will this not help any at all? Thanks for the help.
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Old December 7th, 2003, 10:00 AM   #8
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Jeff: Indeed

Jerry: Silver Spring, MD, you?

Steve: Like any other automatic mode, the camera may change the exposure on you during your shot. This looks bad.
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Old December 8th, 2003, 09:47 AM   #9
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Follow up for Jeff

Jeff, I did read the post you linked. Can you tell me what what it means to "pull the video into the bottom stop" in post? How would you accomplish this in Premiere for example? I use 6.5. Thanks,

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Old December 30th, 2003, 07:24 PM   #10
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Geoff/Brian- Exposure.

re; Expose as hot as possible (over expose) without clipping the signal.
I have an xm2, how do i know if im 'cliping' the signal? do you mean a visible loss in detail/quality, or is there some kind of meter on the camera that will tell me this? (ps by exposure we are talking about apeture arent we?!)
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Old December 30th, 2003, 07:52 PM   #11
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Almost -- and this is critically important - exposure is a function of both apeture AND shutter speed.

I.e. if you double the shutter speed (light comes in for twice as long) and you half the apeture (half as much light comes in) then you get the same pictur in terms of brightness.

But the motion will be blurred twice as much, but depth of field will increase.

About clipping: I set zebra levels to 95, and that is a "last warning" before you start to clip.
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Old December 30th, 2003, 07:56 PM   #12
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Thankyou Brian. So basically if you see any of the zebra pattern, you would reduce the exposure a little, and increase it when contitions change?
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Old December 30th, 2003, 08:15 PM   #13
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Many users try to make sure they don't over expose the image by purposely under exposing the image and fixing it in post. But this technique will cause a severe loss of detail.

The expose to the right technique may result in too much shadow detail (shadows too light). This would be corrected by using a color corrector, proc amp or brightness/contrast filter. Various NLE software use different names for the filters so I tried to list several possibilities. After Effects would also work.

Zebra bars would work, as well as a waveform monitor. Lacking either of those a well calibrated monitor would aid.
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Old December 30th, 2003, 08:15 PM   #14
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Sure thing Michael. The way I understand it, with a zebra pattern set at 95, the pattern shows up when you are 95% of the way there to being clipped. So a little bit of zebra is healthy. Deciding what level to set your zebra to is a personal choice -- some may set it to 80%, and they would naturally have more patterns on the average day.
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Old December 30th, 2003, 08:34 PM   #15
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cheers brian n jeff. I think i may lock up the shutter speed for a while and just experiment with the apeture, n zebra set at 95 on manual focus. Seems to be a safer option as i try to develop a feel for the camera.
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