Faux Coloring with Layers in the GIMP

[xpatUSA]

I've been a global-only image adjuster for years. Not even merging other than in exposure/focus stacking.

However this week I've started playing with Layer Masks in the GIMP. My brain still hurts.

Today, I made the sun rise in the North!

Starting with this original late-afternoon shot of my street ...



... I converted it to grayscale:



The GIMP has quite a selection of gradients, including "sunrise", which I applied to the grayscale as a mask:



I wasn't too happy with the result, so I masked in some of the original with a black-to-white gradient:



Looks like it's a work-in-progress but I'm quite pleased so far.

comments welcome!

[DanK]

Now that you have started: there is no turning back.

As long as you can move the sunrise to the north, can you make certain things disappear from the District of Columbia?

[xpatUSA]

Now that you have started: there is no turning back.

It was our discussion re saturation that me going, Dan.

As long as you can move the sunrise to the north, can you make certain things disappear from the District of Columbia?

I wish.

[Stagecoach]

comments welcome!

With any work like this Ted the main thing is the accuracy of the selections and tree/foliage interface to the sky which is critical.

Whilst I rarely 'modify' images other than 'adjust' existing data in specific areas I have found that luminosity masks make this a doddle in examples such as yours.

Here's two minutes work with one luminosity mask on your original, something that would have been near on impossible using global adjustments, standard selection methods or manual brushing.



Learning the techniques has kept me busy during these times that I can't get out shooting new pics.

[xpatUSA]

With any work like this Ted the main thing is the accuracy of the selections and tree/foliage interface to the sky which is critical.

Whilst I rarely 'modify' images other than 'adjust' existing data in specific areas I have found that luminosity masks make this a doddle in examples such as yours.

Here's two minutes work with one luminosity mask on your original, something that would have been near on impossible using global adjustments, standard selection methods or manual brushing.



Learning the techniques has kept me busy during these times that I can't get out shooting new pics.

Not sure what you're showing me here, Grahame?

Here's about 5 seconds global work on the original in Fiji (ImageJ):

[Stagecoach]

Not sure what you're showing me here, Grahame?

The two things that struck me with respect to your No 3 & 4 image are;

a) that the orange (mod) has bled through to some foliage and tree trunks.
b) that there is a distinct 'halo' appearance around the tops/edges trees, specifically in the centre area.

My example, is a demonstration of masking that can allow change to be made in one area (sky) that does/did not affect the rest of the image or give the 'halos'.

[xpatUSA]

The two things that struck me with respect to your No 3 & 4 image are;

a) that the orange (mod) has bled through to some foliage and tree trunks.
b) that there is a distinct 'halo' appearance around the tops/edges trees, specifically in the centre area.

My example, is a demonstration of masking that can allow change to be made in one area (sky) that does/did not affect the rest of the image or give the 'halos'.

Got it.

I've yet to get into the area-selection side of masking, there being a billion ways to select stuff in the GIMP. So now I see that, had I manage to select the sky in the original, I could have placed the sunset gradient there and nowhere else.

Thanks for taking the time, Grahame!

[Manfred M]

there being a billion ways to select stuff in the GIMP.

Not just Gimp, but the same thing goes for other pixel based editors like Photoshop and Affinity Photo.

If you are trying for a realistic look, one has to be very careful not to leave a trail of what one of my teachers calls "breadcrumbs", i.e. small errors that even a casual observer will pick up on to suggest something looks "wrong" with the image. Frankly, I find it much more challenging to pull off a significant "fake" than to get it right in capture in the first place. Grahame is 100% right that the areas of sky where it meets leaves of trees can be incredibly challenging to to do well (much like background replacements with people, there where the background and hair meet is where one sees the "breadcrumbs".

The other problem one commonly sees in sky replacements is errors in how the sun illuminates the scene versus how the replacement sky is lit.

Have fun Ted; this is the part of post-processing I enjoy.

[DanK]

Indeed. Getting good selections where borders are important and complex is a huge PITA, and I find I don't do it well. It requires good fine motor coordination and patience as well as postprocessing skills.

One option in many circumstances is to feather the edge of selections, but that doesn't always work. One benefit of luminosity masks, which Grahame mentioned, is that they are almost always self-feathering because transitions of luminosity are usually gradual. However, that doesn't always work for a given edit.

[xpatUSA]

Thanks gents for all your helpful comments. I've a lot to learn about selection modes and options - Very hard going while learning layer masking at the same. In the below, for example, I got the mask the wrong way round initially and had to invert it, grump.

I'm making progress, I think:



Two layers - with an an exaggerated gradient just for testing! Plenty of mistakes at the transition from trees to sky ...

I find Layers and Masks very hard going but amazingly powerful. I intend to use them for special effects while still using global editing for "normal" shots.