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### AuthorTopic: Colormanaging scanned negatives - How to do best ?  (Read 21628 times)

#### Mark D Segal

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##### Re: Colormanaging scanned negatives - How to do best ?
« Reply #60 on: February 22, 2012, 12:03:13 pm »

It appears applying a high gamma as I did comes close to what happens if the white point has been set properly. .

Could be - looking forward to what you find.

And yes, the black point should be remapped to neutral black by removing the mask if done from unexposed film.
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....."

#### Christoph C. Feldhaim

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##### Re: Colormanaging scanned negatives - How to do best ?
« Reply #61 on: February 22, 2012, 03:19:24 pm »

I have played a bit with the gamma and the transformation a linear curve can get by applying gamma.

The formulas:

Gamma (Yellow):  y= x^Gamma

Red linear:    y= 0.8x+0.10
Green linear:  y= 0.8x+0.20
Blue linear:   y= 0.8x+0.25

Red corrected curve:   y=0.10-(0.8x+0.10)^Gamma
Green corrected curve: y=0.20-(0.8x+0.20)^Gamma
Blue corrected curve:  y=0.25-(0.8x+0.25)^Gamma

I have not yet an  idea what it means, nor am I sure if have applied correct x and y values, but if I'm not mistaken values from gamma acrobatics are normalized to values between 0 and 1.
This is as a help for thinking what might have happened above.
No idea if it has any declarative value.
I also am not sure if I did the subtraction correctly.