Jump to content
Sign in to follow this  
dmstraker

AP: Saturation mask (experimental)

Recommended Posts

I've been puzzling over how to create a saturation mask, where the darkness/lightness mask represents the saturation of the colours. You can select by hue and luminosity, but not by saturation level, which is a shame as it is possible in PS. Here's what I did, with images.

Note: All adjustment layers are above the image, with the whole set collected in a group.

Initial image has overlaid strips of RGBKMYC, fading from white and to black. They are at greatest saturation in the middle, so we should see this being selected.

akit1.thumb.png.330d286456aa761567ec6f79166fcbec.png

First step is to add an HSL layer, dragging Saturation to zero. Then set Blend Mode to Subtract.

akit2.thumb.png.038ba465f503733cbce60b6a8245d169.png

Here we can see the central areas of the strips are coming through, which is what we want (I tried Difference blend but it wasn't the same).

There's more detail in there, but we can't see it at the moment, so add an Invert layer.

akit3.thumb.png.e0b80c25a2f1e940506116ee188074c3.png

To make it black and white for masking, add a Black/White layer.

akit4.thumb.png.a996cd6f2714f003da049dcbe8c26d62.png

This is all rather faded, so add a Levels layer and drag the Black up to meet the histogram and improve contrast.

akit5.thumb.png.91934a44d3c492c3d9fe2a243e8f061b.png

We can now create a mask from this. Invert it again if you like to select the more saturated colours.

Here's a quick example, with the mask loaded to a Curves layer which has been pulled up to affect lower saturation areas (note the lighter and darker areas of the strips are lifted) but higher sauration is not (as can be see in reds such as the draining board stand).

akit6.thumb.png.54cdd121d96c874daaf9164ca660425a.png

As this effectively converts saturation to luminosity, areas of it can be selected with Blend Ranges, for example just the most or least saturated.

The principle could also be applied to any other adjustment, subtracting it from the original and turning this into a mask.

Bottom line - does this make sense? Have I fallen over any tripwires?


Dave Straker

Cameras: Sony A7R2, RX100V

Computers: Win10: Chillblast Photo with i7-3770 + 16Gb RAM + Philips 40in 4K; Surface Pro 4 i5

Favourite word: Aha. For me and for others.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×