How to Edit Masks Directly in Layers Panel?

[Mark Oehlschlager]

I've been struggling to understand the Affinity method for creating and editing alpha channel masks in a way that doesn't involve 5-8 steps, right-clicking my way though the channels panel.

In Photoshop, one can target a layer mask directly in the Layers panel and manipulate it. For example: 

Not so in Affinity Photo. For example, I can't select a layer mask in Affinity Photo and apply Dodge or Burn tools to refine the mask. And there seems to be some mysterious difference in the way that masks created by the Affinity Refine Selection function and the way a greyscale layer that is clipped to another pixel layer functions.

I'm so confused by it all.

What am I missing?

 

[Lee D]

The workflow shown in the first part of the video can be done within Affinity Photo as we also have the Minimum and Maximum filters available. The same applies to how to use the Blur tool on a layer mask. When it comes to using the Dodge and Burn tools we recommend a different workflow but one that is used in PS as well. Using a 50% grey fill layer with blend mode applied, see this video for a demo.

[Mark Oehlschlager]

@Lee D

I'm beginning to understand the Affinity approach. 

For example: 

1) a greyscale layer dropped to the right of an image layer will not mask according to greyscale values, rather according to whether or not there is pixel data present – white, grey or black.

2) only Layer Alpha channels from the Channel Panel can be used as a source to create a Mask Layer or a Greyscale Layer. Neither color channel information, nor the Composite Alpha channel can be used as a source to create a Mask Layer or a Greyscale Layer.

3) Spare channels can be loaded into empty existing Mask Layers, but cannot be used as a source to directly create a Mask Layer.

With regard to the Minimum and Maximum filters, I was thrown by their categorization under Blur filters and missed them.

REMAINING QUESTION

With regard to the challenge of dodging or burning the values of a Mask Layer, the demo you cited above doesn't seem to apply. How does one go about dodging and burning the values of  Mask Layer in Affinity Photo?

[Ron P.]

I've tried using the Minimum and Maximum (blur) filters in AP, and they appear to act differently than the Minimum & Maximum filters in PS. Applying them in AP, they blur the whole selection/image, not just the fringing. Am I missing something that constrains the blur to just the outline/fringing?

EDITED....

I found the answer in a post by Julieanne Kost, where she specifically explains what those filters do, and how to use them to reduce or expand a selection.

Quote

Although it is easy to use Select > Modify in order to expand or contract a selection by a specific number of pixels, for additional control, try using the Maximum and Minimum filters. To contract or expand a selection by a decimal number (not a whole number as is the limit for the Select > Modify command), first, make your selection, then click the Quick Mask icon to view the red overlay before selecting the filter (otherwise the filter will effect the pixels in the photo that you have selected). Then, choose Filter > Other > Minimum to contract the selection by a non-whole number or choose Filter > Other >  Maximum to expand the selection by a non-whole number.

Note: both of the filters are looking at the values of gray within the specified radius that you define. The Preserve Roundness option  will help keep round shapes round instead of being reduced using a more “rectangular” method which will cut corners when contracting. The Preserve Squareness will help keep rectangular shapes with more square edges from getting rounded. Both filters can be used for choke and spread operations on masks or images (removing dirt, enlarging bright points, etc.).