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Author Topic: Visualizing Exposure Settings As Curves?  (Read 1660 times)

dtronvig

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Visualizing Exposure Settings As Curves?
« on: August 06, 2016, 11:46:59 pm »

Correct me if I'm wrong, but I'm guessing that each of the controls on the Exposure tab (except for Saturation and Clarity) applies its own Input/Output curve in turn, and that the whole chain of those individual curves defines an underlying aggregate curve that is applied to the input before it reaches the visible Curve tool. If that's about right, then is there a way to look at the shape of the individual curve applied by a given control? I'm not talking about seeing the curve applied by a given control on a given variant, just the generic shape of the curve applied by that control.

If you started with an image with a linear 0-255 gradient, you could apply controls and get an idea of their effects by looking at the resulting histogram, but I haven't figured out how to translate that to an underlying Input/Output curve, if in fact that's the way that the controls work.

There's probably nothing about this that would necessarily be related to Capture One in particular. If there's no trick within Capture One to do this then maybe some external software that might, say, take the modified output from that gradient image and work out the input/output curve that produced that modified image.

Any suggestions?
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Guillermo Luijk

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Re: Visualizing Exposure Settings As Curves?
« Reply #1 on: August 07, 2016, 04:52:47 am »

I reverse-engineered the different tools in Photoshop. Take into account that not all processes can be modelled with a RGB curve and C1 could work in different ways:

http://www.guillermoluijk.com/article/acrps/index.htm


I also wrote this piece of software that calculates the RGB curves used on toned B&W images:

http://www.guillermoluijk.com/software/tonehacker/index.htm


The same routine, but giving an input and output image, calculates the RGB curves that best model the process. I used it here to approximate camera tonal curve:

http://forum.luminous-landscape.com/index.php?topic=96758.0

Regards
« Last Edit: August 07, 2016, 05:06:28 am by Guillermo Luijk »
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dtronvig

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Re: Visualizing Exposure Settings As Curves?
« Reply #2 on: August 07, 2016, 05:37:23 pm »

Ooooo, that looks great. I'll work through that.
Thanks, Guillermo.
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David Grover / Capture One

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Re: Visualizing Exposure Settings As Curves?
« Reply #3 on: August 08, 2016, 05:36:04 am »

Correct me if I'm wrong, but I'm guessing that each of the controls on the Exposure tab (except for Saturation and Clarity) applies its own Input/Output curve in turn, and that the whole chain of those individual curves defines an underlying aggregate curve that is applied to the input before it reaches the visible Curve tool. If that's about right, then is there a way to look at the shape of the individual curve applied by a given control? I'm not talking about seeing the curve applied by a given control on a given variant, just the generic shape of the curve applied by that control.

If you started with an image with a linear 0-255 gradient, you could apply controls and get an idea of their effects by looking at the resulting histogram, but I haven't figured out how to translate that to an underlying Input/Output curve, if in fact that's the way that the controls work.

There's probably nothing about this that would necessarily be related to Capture One in particular. If there's no trick within Capture One to do this then maybe some external software that might, say, take the modified output from that gradient image and work out the input/output curve that produced that modified image.

Any suggestions?

Wrong!  ;)

Exposure, Brightness and Contrast may follow in some ways what you can do in principle with a curve, but you cannot necessarily replicate it due to the algorithms in play by those sliders.
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David Grover
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