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I'm trying to repeat a Blend If 'Underlying Layer' blending with a mask. I have a background layer with some shapes and an orange layer:

enter image description here

I set the dark levels of Blend If to 90/130:

enter image description here

I've tried two ways: using levels (didn't work, especially for cases when the little slider thing isn't separated) and using a gradient map. For the gradient map I've set markers to be at 90/255 ~ 35% and 130/255 ~ 51%

enter image description here

The resulting mask:

enter image description here

However the result is slightly more transparent (there's a visible seam between two versions):

enter image description here

That could be caused by the fact that gradient map can only use integer locations in 0..100 range while the Blend If mask uses a 0..255 range: the actual locations should've been 35.29% and 50.98%. Or maybe I've made a mistake with something. I wonder if anyone has any suggestions on how to repeat the result of this Blend If operation so that it'd be completely the same.

Here's the .psd if anyone wants to try.

  • Oh I think I made the image with the seam confusing: there's no seam in the images, those are two results put together against each other: the top part is the orange layer with the gradient map I got and the bottom part is the original Blended If layer. I put them together to better illustrate a slight difference. I've updated the image. – Sergey Kritskiy Oct 7 at 19:12
  • Ahh.. yes clearer now :) – Scott Oct 7 at 19:17
  • I'm not sure I get what the problem is. Why not use the gradient map if it works better? – Luciano Oct 8 at 8:34
  • @Luciano the Gradient Map I'm generating gives me a slightly different transparency gradient and I want to get exactly the same transparency gradient – Sergey Kritskiy Oct 8 at 9:29
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Ok, I think my approach was correct, but default Photoshop Gray color correction (Dot Grain 20%) was making additional modifications to the mask gamma. Setting Gray Working Color Space to Gray Gamma 2.2 before applying the gradient mask has fixed the difference between Blend-ed If and masked layer.

update: nope, doesn't give 100% correct results

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  • What? I never thought about Gray Working Space affecting things like this! I downloaded your file and see how choosing Gray Gamma 2.2 gets you closer than Dot Gain 20%, but they still don't look exactly similar to me. – Wolff Oct 9 at 17:54
  • @Wolff in a document with white BG create a gray (50% brightness) layer and select+cut it. Fill the empty layer with black color, add a layer mask and paste that copied gray layer in the mask. Sample the resulting gray color. You'd expect that it will have 50% brightness (100% black - 50% values of gray mask), but it will be 59%: due to gray correction gamma. With Gray Gamma 2.2 the result will be correct – Sergey Kritskiy Oct 9 at 18:25
  • @Wolff however yes, in the end the gamma didn't resolve the issue I have. Depending on BlendIf values I still see the difference between the blended and masked layers. So I won't accept my answer :D – Sergey Kritskiy Oct 9 at 18:26
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So I'm not exactly sure why or how the math isn't working exactly, but I was able to get it to work with a minor adjustment. I DID adjust my Gray Working Color Space to the Gray Gamma 2.2

Other than that, the only adjustment I made was to change the Gradient map overlay by 1% either way. So instead of setting for 35% / 51%, I set for 34% / 52%.

Black Slider White Slider

Final Result:

Final result

Showing Divide Line:

Showing line

Since changing the Working Space profile changed the results so much, I played with a couple different settings and got different results every time. Using the default 20% Dot Gain profile was way off as you saw. The 30% dot gain was better, but still not perfect.

30% Dot Gain Profile

With all of that in mind, using the canned Gamma 2.2 profile and adjusting your match by 1% out seems to be the best solution. I tried the match for a couple different Blend If positions, and the shift by 1% isn't exact, so you would need to check what exact percentage you need if you change the original Blend If.

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  • Thank you for reply. So if I understand you were eyeballing the gradient map? I want to do the whole thing with a script so manual adjustments aren't ideal... I have another idea: maybe I should modify colors of the gradient map, will try that layer – Sergey Kritskiy Oct 15 at 16:33
  • Not exactly eyeballing, but changing the settings slightly one way or the other to see if I could get it to match. are you always using the same color / look? If so, you should be able to script it, or is it something that will be changing all the time? – Alith7 Oct 15 at 16:46
  • changing the colors of the gradient map isn't the worst idea either. – Alith7 Oct 15 at 16:47

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