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struggling to understand gamma

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Peter Northall
struggling to understand gamma
on Apr 27, 2015 at 3:35:35 pm

...specifically with regards to the c300, c-log and the info on the wave form monitor.
I view a grey scale card on the WFM; with 'normal' gamma the scale is spread from below 5% (black) up to almost 100% (white) with mid grey about 50%. I get this, the WFM image shows me which bits of my chip are being tickled by the light (and how much).
Then I switch in c-log. Mid grey pushes down to 30% ish, black to 5-10% and white to less than 60%.
I know the file needs a LUT/post to look any good, but why has this exercise increased my latitude? What has happened to all that unused 40% highlight area on the WFM? Surely I should be using all the 100% to get max latitude? I'm missing something simple here (doh for sure).
Someone help me get this, please...

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john sharaf
Re: struggling to understand gamma
on Apr 27, 2015 at 3:44:58 pm


Simply put, the C-Log compresses the highlights down to 70% leaving room for even brighter parts of the scene to be recorded before clipping off at 100. That's why the picture looks washed out and gray; because lowering (or chrunching) the gamma also desaturates the color, in the LUT or Color Correction the saturation is raises to compensate.


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