Masks - Can't seem to get it right

[AceMcHammer]

(08-10-2025, 05:34 PM)Ofnuts Wrote: You don't need a "mask" (or at least not the "mask" concept as understood in Gimp). .There are plenty of tools to shift colors slightly.

* Colors > Color temperature an increase the intended temperature slightly (this is a prime candidate if you have two image that are likely two photos of the same source, but taken with a slightly different white balance)
* Colors > Hue chroma and slightly reduce the hue
* Colors > Hue saturation

The ultimate tool for this is a CLUT, using the GMIC plugin. Using the before and after images it will produce a Color Look-Up Table (CLUT) that maps the colors between the two images. With the same plugin you can re-apply the CLUT to a different image to obtain the same result (in theory, in practice you can only apply it to a similar image, a CLUT created using an image with plenty of reds  may not give good results on an image with plenty of blues.

I know the Color Temperature adjustment well and use it often to make images look warmer or cooler but the color temp alone will not create the effect of that "sepia" mask or of that slight brownish mask.  

I actually tried to duplicate the effect using all my usual adjustments of Hue Saturation, Color Temp, Brightness Contrast, Chroma, Color Balance, Exposure (black level), Curves and this is what I came up with without a mask.....



..which looks pretty close but it's still not like the other image.  I had to go to Hue Saturation and adjust the "Hue" of the red, yellow and magenta I believe mostly get it to look like that.  I basically concentrated on matching the color of the sail masts.  But in the other image I can tell by the lines in the sails look darker and the also the color of the water that it's probably a mask.  Even the water has that slight sepia tint.  I can bring out the lines in the sails a bit more with contrast but then brighter areas start to loose detail.  And that's another reason I think it's a mask in the other image because the of the darker lines in the sails without overexposure of bright areas.

I do have the GMIC plugin but have not tried the CLUT option.

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(08-10-2025, 05:48 PM)rich2005 Wrote: Looks like you might get it with an HDR effect.  There are plugins around for Gimp 2.10 but pure Gimp

Try: Colors -> Tone Mapping -> Mantiuk2006 with settings as shown:



It is not a very fast effect, so for a large image, be patient.

Trying to set the contrast and saturation adjustments that you showed with the dialogue of that effect froze my computer up 

(08-10-2025, 07:33 PM)rich2005 Wrote: Another one that might be of interest.  There are two effects Dragan and Dave Hill, if you search there are methods for these.

Using Gimp 2.10 a very old plugin, (attached) Put it in your plugins folder. Find it on the menu bar - PythonFu.  Unusual in that it gives advice as it runs and it does use masks.  Edit: playing around, sometimes the "advice" dialogues pop-under the main Gimp window - just as long as you know.  For a trial just run through to the end and on the top layer adjust color/hue-chroma

I'll give that a try too.