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How to reverse engineer a tone ?

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Old 04-13-2012, 10:04 PM
nextgen2012 nextgen2012 is offline
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Join Date: Mar 2012
Posts: 18
How to reverse engineer a tone ?

I run into this question a lot. Given a photo - how do you find which tone was used ? Detecting sepia or blue tones is quite easy - eyes are used to it. But detecting others is do you find it..using CMYK values in PS ? I tried but that didnt give me a hint.

Also, on the similar topic - how many folks warm up the highlights and cool down the shadows in BW toning ?

This is the latest pic that I want to reverse engineer the toning for:

Thanks for the help!
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Old 04-13-2012, 11:43 PM
redcrown redcrown is offline
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Posts: 87
Re: How to reverse engineer a tone ?

For mono toned images like the sample you gave, I prefer to work with RGB values to reverse engineer the tone.

On the "toned" sample, take three samples. One in the highlights, one in the midtones, and one in the shadows.

To do that, I like to put 1 of the 2 Info Pallet readouts in "Grayscale" mode. Then grab the Color Sampler tool, put it in 5X5 sample size, and fish around on the image for a good highlight whose K value is 15% to 20%. Put down a sample point.

Do that again, looking for a midtone with K value of 50%. Put down another sample point. Then find a shadow with K value about 80% and put down a 3rd sample point. Using K values just makes it easier to find good sample points. Look at and record the RGB values for those 3 sample points.

Next, dupe the background and desat that dupe layer. Now look at the 3 sample points for the desat layer.

To emulate the tone, build a Curves adjustment layer and make adjustments to each individual channel do "drive" the values from the desat layer to the values of the toned layer.

In your sample, I grabbed a shadow value from the dark shirt of the girl on camera right. Got toned RGB values of 37/49/54 and a desat value of 45. Grabbed a midtone from her pants, got toned values of 119/130/131 and a desat value of 124. Highlights from Mom's right arm gave toned values of 218/219/211 and a desat value of 215.

So, build a Curves adjustment. Select the Red channel, add three points. One with input of 45 and output of 37, one with 124/119, and one with 215/218. Repeat for the Green and Blue channels. Each with 3 points where the inputs are from the desat values and outputs from the toned values.

Now you can copy that Curves Adjustment to any other desaturated image (maybe make it a preset) and you should get a close approximation of the tones in the sample. Won't be perfect, but close. Depends on how fancy the original author got with split toning.

You were on the right track in your evaluation of this image. In the shadows and midtones, the Blue value is greater than Red and Green. But in the highlights, Blue is less than Red and Green. Signs of a split-tone.

Footnote: You can't download the sample you pointed to, so I had to do a print screen and paste into Photoshop. That means the RGB values I got were the result of my personal monitor calibration, and were in sRGB. You will definitely get different values based on your calibration profile and colorspace. But the concept will still work.
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Old 04-14-2012, 01:14 AM
nextgen2012 nextgen2012 is offline
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Join Date: Mar 2012
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Re: How to reverse engineer a tone ?

That was the best reply I could probably get. Thanks bunches !!
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Old 04-14-2012, 03:58 AM
ShadowLight ShadowLight is offline
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Join Date: Oct 2009
Posts: 397
Re: How to reverse engineer a tone ?

select half the image, create gradient map layer
start adding colour points to the gradient by selecting from the original image, and placing them at the proper location to match the original.

when you are done, delete mask.
(togging the gradient-map layer should be giving you the same image with no changes)

get new image, copy the gradient-map layer over it
(I imagine you may need to add contrast/brightness adjustment below the gradient map to get the luminosity right, or even curves and just adjust the main RGB for lum corrections)

good luck

Last edited by ShadowLight; 04-14-2012 at 04:10 AM.
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