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Adam D'Agosto

How to adjust contrast of a mask (not the curves itself)

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Hi.

Having some trouble....can someone guide me.

After creating a luminosity mask for the shadows and a separate one for the highlights, I want to create a new curves layer and go deeper into each. What I need to be able to do is adjust the contrast of the mask itself, not the actual curves layer. How do you do that?

In Photoshop, the way I'd do this is after creating the luminosity mask I could go into Image....Adjustments....Curves and then be able to adjust the contrast of the mask only.

Is there a way to do this in AP?

Thanks!!

Adam.

 

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If I understand your question correctly, the problem is that Affinity Photo handles channel editing much differently to the way that Photoshop does it. And, editing masks is particularly troublesome.

My understanding of this is that Photoshop allows the user to edit channels as if they were greyscale pixel layers. That means that all the pixel tools (all of the brushes, adjustments, and so forth) can be used directly on channels in the same way that they would when working on a traditional pixel layer. However, Affinity Photo is different, especially when it comes to editing the Alpha channel of a mask. Affinity will not let you directly apply all but a very few types of edits right to the alpha channel; AP treats the mask channel as alpha elements, only, and does not let you edit it the way you would a more typical greyscale pixel layer.

You can, however, add a Levels or Curves adjustment to a mask. Add a Curves layer, for instance, and drag it over the Mask thumbnail in the Layers panel so that you get the vertical blue bar. In the Curves dialog box, choose "Alpha" as the channel to be manipulated (rather than the default choice of "Master"). You can directly adjust the mask in this way, and it is effectively a non-destructive layer.

If you want to edit the Mask itself, however, in a more destructive fashion, you have to temporarily turn the mask into a pixel layer. In the Layers panel, right click on the mask thumbnail, then right click on the "Mask Alpha" in the Channels panel. Choose "Create Greyscale Layer" Drag this new layer up to the top of the stack. Now, add a Curves adjustment and adjust the greyscale layer as you'd like. Click the "Merge" button to change the pixel layer destructively. After that, right click on the pixel layer and choose "Rasterize to Mask." Drag this new mask into your photo, and replace the old mask.

The video below demonstrates this. I took a photo and created a "Darks 1" luminosity mask. (I kept all this in a Group to be able to compare at the end.) After duplicating the Group, I created a greyscale layer out of the duplicated mask and applied a Curves adjustment. I merged this, rasterized it to a mask, and dragged it into the duplicated Group.

Compare the New version and the Original version when I turn the Group on and off. Also, compare the masks when each is viewed in "Isolation Mode."

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A workaround, without the need of an additional layer, might be to use "Refine Mask..." just for editing its contrast, mainly with the Ramp value.


macOS 10.14.6, Macbook Pro Retina 15" + Eizo 24", Affinity in Separated Mode (documents merged)

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Another, probably more convenient and more suitable option than "Refine Mask..." – but also without creating an additional layer –, might be the "Blend Range" option, which is available for instance if your mask is painted directly on your "Adjustment" layer. (It's not available for a "Mask" layer.)


macOS 10.14.6, Macbook Pro Retina 15" + Eizo 24", Affinity in Separated Mode (documents merged)

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Tying to get this to work

"You can, however, add a Levels or Curves adjustment to a mask. Add a Curves layer, for instance, and drag it over the Mask thumbnail in the Layers panel so that you get the vertical blue bar. In the Curves dialog box, choose "Alpha" as the channel to be manipulated (rather than the default choice of "Master"). You can directly adjust the mask in this way, and it is effectively a non-destructive layer."

However when I create a mask layer and attach either a curves or level adjustment I see not visible effect to the mask, I would expect to alter the attached curves / level and then view the mask layer by alt-Clicking on it's thumbnail to see the effect of the level/curves.  Am I missing something ?

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1 hour ago, solsticephoto said:

However when I create a mask layer and attach either a curves or level adjustment I see not visible effect to the mask,

This could be related to your layers hierarchy and their way of being nested.

Here is another example, with a different approach in the workflow than the video above. It uses the layer Blend Range Options to refine how an adjustment layer affects the image. To access them click the cog icon. Note that this does not alter the adjustment setting but influences its levels only. It works like mask for an adjustment, masking related to the images levels. Blend Range Options are not available for a (Mask) layer itself.

In the beginning you see the image without adjustment –> then with level adjustment (brighter) –>  mask activated –> blend range options.

 


macOS 10.14.6, Macbook Pro Retina 15" + Eizo 24", Affinity in Separated Mode (documents merged)

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