Preserving delicate cloud details against sky background

Many of my photos include clouds. Often, when I’m tweaking the sky color/density, I notice unwanted changes in the areas where the edges of clouds transition to sky.

In such a situation, what work-flow decisions would you make?

Example image (completed) …

Are you using any kind of selection mask? I would definitely try to obtain a mask. For instance, starting from the red component, which is weaker on the sky, you can find what he red value is on most of the sky (X=51) and make a bell-shaped curve around it to exclude the clouds.

The edges of the clouds correspond to the slopes of the bell and so a partially selected, the effect on the cloud is very progressive.

Well, my selection process appears to be crude. I’ve either used the fuzzy select tool or luminosity masks. But, the process you’ve shown and the color curve graphic is new to me. I guess this is why I seek this forum.

@Ofnuts I will tinker with this new info for several days!

This is basically an improvement on luminosity masks:

  • You use a specific color channel (or any grayscale image obtained using the channel mixer)
  • You use a Curve to define the area instead of operations which allows you to set them exactly where/how you want (the operations defined in PatDavid’s canonical tutorial can be done in Curves too, with straight lines at specific places)

Btw if you use Luminosity Masks in Gimp you can have a look at this

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can i ask why you’re not using a RAW workflow? just curious or if you are, why finish in gimp?

@David_Prescott I’m switching between RAW files from a Canon Rebel and “RAW” or JPEG files from iPhone apps. A few images start as Canon RAW, and some start as JPEG.

Years ago I had a budget for a 4x5 camera, and nowadays I’m sometimes struggling to get a similar level of quality. That won’t happen. The 4x5 spoiled me.

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One more thing. Sometimes RawTherapee ticks me off. I would like some way to correct iPhone wide-angle lens distortion, but the software seems limited to DSLR lens lists.

This is not a RawTherapee issue but a lensfun limitation (which is used by RawTherapee).

I just had a look at which iPhones lensfun supports: 1, the iPhone XS. And only the 4.25mm f/1.8 and 6mm f/2.4 back camera.

You could upload a RAW and create a ticket to get it included (Lens calibration / Upload calibration pictures).