how to do an overexposure test

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Chris Shivers

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  • Joined: Sat Jul 01, 2017 3:12 am

how to do an overexposure test

PostTue Jun 22, 2021 5:03 pm

I'm not sure if i'm not understanding it but when i over expose within the recovery boundary i cant recover anything. I just did another test to see maybe if i was over the exposure threshold but nope. I did 1 stop over exposed and i still cant recover it. This is the way i tested. i shot a window, and i know in order to be properly exposed i had to shoot at f/22. So i wanted at least three stops to be recovered so i shot it at f/5.6. So in theory it should recover to the point where it looks like it was shot at f/16, or at least close to it. I shot both in pro res and braw. In braw i shot it as f/5.6, iso 400, shutter angle 180. In pro res i upped the iso at 800 since it has more recovery in the highlights, to compensate i lowered the aperture to f/8, shutter angle is still 180. I couldn't recover anything with the pro res or braw. I only recovered some tuff with braw when i clicked the high light recovery, but it was minimal. What am i doing wrong? I should at least recover 3 stops.
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Mike Potton

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Re: how to do an overexposure test

PostWed Jun 23, 2021 12:14 am

It's hard to follow exactly what you're trying to achieve with your tests, perhaps some images would help. If you're trying to 'recover' data out of clipped segments of your image you're attempting the impossible.

To simplify things put your camera into film mode and turn on false color. Anything red is hard clipped. Braw 'highlight recovery' might be able to pull out a small amount of data using unclipped channels but don't rely on it.

Iso (except for the dual iso bands on the pocket series) has no effect on dynamic range. Simply cycle through your iso's and note that black clipping and white clipping remain the same.
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Chris Shivers

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Re: how to do an overexposure test

PostWed Jun 23, 2021 12:53 am

Mike Potton wrote:It's hard to follow exactly what you're trying to achieve with your tests, perhaps some images would help. If you're trying to 'recover' data out of clipped segments of your image you're attempting the impossible.

To simplify things put your camera into film mode and turn on false color. Anything red is hard clipped. Braw 'highlight recovery' might be able to pull out a small amount of data using unclipped channels but don't rely on it.

Iso (except for the dual iso bands on the pocket series) has no effect on dynamic range. Simply cycle through your iso's and note that black clipping and white clipping remain the same.

Oh, I’m just now noticing all the test I’ve seen is with the footage graded, I feel stupid. I’m thinking it was clipped with log footage
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lost_soul

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Re: how to do an overexposure test

PostWed Jun 23, 2021 10:15 pm

When trying to recover maximum range make sure you don't use an import transform or a LUT at the front of your color correction chain. Do tthe recovery up front and then put the transform or LUT after it.
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