When modifing the selection in a Photoshop layer mask, the modifed region has a different density th

[Bill Junk]

I have used the Sky selection feature on Layer 0 to select the sky in a photo.  However it did not select a portion of the sky that was gray and needs to be included.  I then used the Polygon Lasso Tool to add the area that wasn't included and then applied the modified selection to a new Brightness/Contrast Layer.  The added area is shown with a different density and clearly stands out from the rest of the selected area.  What am I doing wrong?

[Bojan Živković]

Can you post a screenshot to illustrate the issue? If you Alt/Opt + click on the layer mask, it should display in full size on your screen. Do you notice any differences in the mask at that specific portion (black and white) compared to the rest of the image? Use Alt/Opt + click on the mask again to return to normal view.

[Bill Junk]

Thank you for your reply.  Here’s the image in Photoshop 26.1.0  (Beta) after I’ve applied some simple contrast, highlights, and shadows adjustments with Camera Raw to Layer 0 configured as a Smart Object.

What I then wanted to do was enhance the contrast in the sky to make it look more dramatic.  I then was use Photoshop to Select > Sky in the hopes it would be quicker than trying to use another tool to get close to what I wanted to select for a mask on a Brightness/Contrast or Curves layer.

I assumed that the “marching ants” defined the area that Photoshop considered to be the sky and that everything within the "marching ants" was fully selected.  More on this later.  There are a couple problems with the selection.  I realize that this image presents some challenges for an automated tool because there is little differentiation in color or brightness between the pre-sunrise sky and low hanging clouds, fog, and even a couple mountain tops.  In the middle of the image there is a small portion of the sky that was not selected automatically.  I assume it was because of the presence of fog and mist.  I wanted to add that missing area to the selection.  There were also section of the clouds and mountain tops that were selected when I didn’t want them selected.  Later on I will delete those areas from the selection, but that is not part of the issues I’m trying to understand and resolve.  In the following image I’ve zoomed in and used the Polygon Lasso Tool to add to the selection between the two mountain peaks to add some sky that was missed.

The selection above has the “marching ants” where I expected them to be in this part of the image.  In the following image I’ve applied the mask to a Brightness/Contrast layer and for illustrative purposes decreased the brightness substantially.  The area that I added with the Polygon Lasso Tool stands out as being much darker although in the original image the brightness is a gradual, smooth gradient from one area to another.

Now doing the Alt + Click on the layer mask shows this:

I learned something here.  It would be a good idea to do the "Alt + Click" on a fairly routine basis just to make sure that what is actually selected for the mask is what I intended.  The area I added to the mask clearly stands out.  It is white while the selected sky is a light gray.  The added selection looks like a setting sun in the middle of the image above.  The next thing I notice is that there are areas outside the “marching ants” boundary of the mask that are selected (they are not totally black), likely partially selected because they are low clouds and of the same color and brightness as some of the "sky", but they are in front of the mountain peaks.   I’m no expert but, it looks like the Select > Sky operation did not fully select all pixels in the main part of the sky.  It seems to have been fooled by the variation in gray tones. To the contrary, the Polygon Selection Tool seems to have fully selected all pixel within its selection boundary and added them to the existing selection.  When the Brightness/Contrast layer was adjusted it had greater effect on the portion of the mask created by adding to the original Sky selection.  I’ve often used the sky selection tool to apply adjustment layers to the sky, but that was mostly done with blue skies and possibly some white clouds with nothing in common with the non-sky portion of the image.  This image is different from others where I’ve had good success with Select > Sky.  I've done a little bit of web searching to see if there are any identified limitations of Select>Sky but so far I have not found any posts.

Thanks in advance for any further insight you might be able to provide.

[Bojan Živković · Accepted solution]

"o the contrary, the Polygon Selection Tool seems to have fully selected all pixel within its selection boundary and added them to the existing selection.  When the Brightness/Contrast layer was adjusted it had greater effect on the portion of the mask created by adding to the original Sky selection. "

You are correct; I would attempt to use Levels on the mask to adjust the gray pixels. Select the mask in normal view, then press Ctrl + L to open the Levels dialog. Experiment with the sliders: dragging the right slider should convert gray tones on the mask to white, while the left slider should do the opposite.

[Bill Junk]

With your help and some experimentation over the last few days I've learned some important things about selection.  I think it is somewhat misleading and unfortunate that Select Sky places the marching ants marker around what appears to be the sky, when in fact it has selected additional pixels outside the marker and in some cases has only partially selected pixels inside the marker.  When I use the Select Color Range tool the selection indicates areas in which a partial selection is present.  Whether or not it always does this is now something I will check.  When partial selection occurs it is nice to see that indicated.   It serves to provide a reminder to verify that it selected what I wanted.

Thanks for the time you've spent helping me.  Do you know of any good tutorials, either written or video, that goes into this level of detail?