image different after frequency separation (darker or lighter)

I just saved the image as a tiff with the Frequency seperation on and one with the FS of and it seems to look the same. So i guess it's actually a display problem in photoshop ?

Please provide a meaningful description of what you are actually doing. 

»when i use the action«

Which exact steps does the the Action comprise of? 

Please provide the atn-file or at least a fully ecpanded screenshot of all its steps. 

Without seeing the exact steps you have taken in your action it is impossible to say what is wrong, but no I do not see that here.

Make sure you, or your action, follow these steps exactly.

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)

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

If that does not work for you - please post a screen shot showing the Apply image settings and the layers panel

Dave