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J
Jerald3046178117xe
Inspiring
June 18, 2025
Answered

Frequency Separation is officially badly broken on Mac M4 Photoshop code set

  • June 18, 2025
  • 5 replies
  • 693 views

Frequency Separation (FS) is a long used method for skin retouching that creates results that superior to just using the healing brushes and clone tool alone. I am using Ps 28.1 on a Mac Studio M4 series silicone. If If I make edites on the highpass/detail layer the pixel replacement removes the texture completely, and produces bright and often inverted color pixels. If I try this on my Intel based MBP using the same version of Photoshop and the Same release of Mac OS, the Spot Healing Brush Tool, Removal Tool, Healing Brush Tool, and the Clone tool work as expected. My guess this would also work correctly for Windows based computers as well.

 

I spoke with product support and they admitted the abilith to use FS to edit photos is completely broken and I could try the cloud version as a workaround. Not a great solution from a workflow perspective. 

 

What do I mean by FS?

1. A duplicate of the image with the High Pass filter applied and the blending mode is set to Linear Light

2. Below that layer another duplicate layer with a Gaussian Blur applied. 

 

This technique allows you to separate the detail edits from the color and is useful for removing skin blemishes, dark circles, or wrinkles on skin or even fabric. 

 

I don't think there is a solution for this problem on the M serices code set unless someone has found a workaround. I am hoping Adobe will either give us a different blending mode that works or fix the issue. Perhaps a legacy option as they have done in the past when updates has broken things. Here is the response I received:

 

"Photoshop introduced updated rendering logic and new blending behaviors in newer versions. Photoshop now applies content-aware blending that doesn’t behave well on high-frequency grayscale data — resulting in artifacts, bright halos, or inverted colors."

 

Anyone else using FS for edits and experiencing the same issue? Are you experiencing the issue on Windows/x86 based systems? 

 

Correct answer Jerald3046178117xe

The problem was with the layer sampling. Even thought I unticked the Sample All Layers with the Spot Healing Tool, I didn't see a difference. At a later time I gave it another go and I am able to edit the detail layer correctly. Same with the Healing Brush Tool. 

5 replies

J
Jerald3046178117xeAuthorCorrect answer
Inspiring
June 24, 2025

The problem was with the layer sampling. Even thought I unticked the Sample All Layers with the Spot Healing Tool, I didn't see a difference. At a later time I gave it another go and I am able to edit the detail layer correctly. Same with the Healing Brush Tool. 

J
Jerald3046178117xeAuthor
Inspiring
June 23, 2025

Here is the Adobe documentation on the Frequency Separation method:

https://www.adobe.com/products/photoshop/frequency-separation.html

E
ExUSA
Legend
June 18, 2025

I use Frequency Separation on many images and have not seen this on an M1 or M3 processor. High Pass is not part of doing FS though, just to be clear.

    J
    Jerald3046178117xeAuthor
    Inspiring
    June 18, 2025
    You’re right about not using a Highness sharpening. I was mistaken. The automated script uses apply Image, which appears like a Highness layer.

    Another correction: the version of Ps is 26.8, not 28.1. (I was anticipating Adobe’s release.) Also, changing the detail layer to Normal blend mode, making edits, and then switching back to Linear Light works correctly. The newer content-aware logic on certain blending modes causes issues.
    J
    Jerald3046178117xeAuthor
    Inspiring
    June 18, 2025

    Hi Dave,

     

    Thanks for your reply. It does not matter if I tick the ☑︎ Sample All Layers checkbox. Actually I am using the same method as you described for the detail layer. I have it setup as a script and have not manually created a FS layer group in a long time and I only edit 16 bit raw files. I manually created the detail layer with the same results. I've seen others complain about this problem; however, by comparing the Mac M series chipset vs Intel did I realize they have changed the way the blendmodes work, or don't work.

     

    davescm
    Community Expert
    davescmCommunity Expert
    Community Expert
    June 18, 2025

    Hi
    No problem here in Windows using v26.8. 
    One question, sorry to ask as you are obviously experienced, is your clone stamp/healing brush set to sample current layer? All layers or current and below will produce incorrect results.

    Just for the benefit of others wanting to test FS on their own system please follow the following steps :

    1. Make 2 duplicates of your image layer
    Name the lower - "Low frequency"
    Name the Higher - "High Frequency"

    2. Select the Low frequency layer and use Filter Gaussian Blur (around 6.0 is often a good starting point)

    3. Select the High frequency layer
    Go to menu Image > Apply Image
    Set the source layer to Low Frequency
    Set the blending mode to Subtract
    Set Scale to 2 *
    Set offset to 128 *
    Click OK

    4. Change the blending mode of the high frequency layer to Linear Light

    5. Now you can clone out blemishes on the high frequency layer and lighten or darken areas on the low frequency layer





    * Note - the above steps are for 8 bit/channel images. For 16 bit/channel step 3 changes slightly

    3. Select the High frequency layer
    Go to menu Image > Apply Image
    Set the source layer to Low Frequency
    Check "Invert" next to channel

    Set the blending mode to Add
    Set Scale to 2
    Set Offset to 0
    Click OK

    Now carry on with step 4 above

     

    Dave

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