False color exposure guide in darktable.

Watching a video tutorial on image editing in ART by Shane Milton, I saw an option to use false color to “technically” correct the exposure of an image.

I transferred this to darktable through the LUTs 3D module, even knowing that it was not going to be exactly accurate since by the design of darktable, that one module depends on the previous one, between the exposure and the LUTs module there were going to be other intermediate modules.

The false color method is used by video cameras, display monitors and some image and video processing software.

DaVinci Resolve sample image using false color

Question: Would it be feasible to request a FR into the Github with this kind of utility for darktable or is it unnecessary? would this method of exposure visualization help to the workflow a little more?

It would be good to know the opinion of people who are familiar with the subject.

Here are some screenshots with part of the process I used to edit some images.

false color using luts

using a mask to isolate overexposed areas in an exposure module

final correction of overexposed zones of the image

I’ve created a .svg file to use as a guide with the false color LUT and imported into the watermark module, of course this is optional. I left the .svg file in this post.

false color used as a guide in a mobile app

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It wasn’t false color but you could get this sort of thing with the zonemapper module… it would show a mask or display of the zones

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Hi Todd, I could no find this module in DT using the search bar.

It’s depreciated. You need an old xmp that used it so that it can be recalled. I might have one…

If it is depreciated then I will let it stay that way. I was just wondering why I couldn’t find it. Thanks

Aurelien was driving the bus on this one I think… the contrast eq was a sophisticated replacement but the simple zone GUI I think worked for some and it had the ability to show what zones where what on the image…

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I found an old style…

Edit

@difrkaguilar Looking at that zone system preview it would seem that someone clever could easily revive some of that code and use false color in place of the L channel of LAB to provide your false color preview…

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I brought this up a while ago (darktable's filmic FAQ - #107 by europlatus) and have always liked the idea. ART has a false colour mask and I really liked it. It’s also quite standard in the video industry I believe, so it’s not a crazy idea.

The zone system module provided similar functionality, but with that being deprecated, there’s now no similar feature at all.

Could that visual feature from the zone system module be somehow ported to a mask so that we can get the functionality back without the full module?

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I have used this module some time ago before it was deprecated. It was nice, but I think it is not the same. But in this case users will see directly on the images the false color and will better define which part is overexposed.

I was thinking more less to be something like a visual guide to be used like clipping, over exposed, gamut and soft proofing visual guides and will works independent of the modules workflow.

The icon with the raw overexposed warning have a false color option, but doesn’t works that way.

raw-overexposed-icon

" false color: Set clipped color channels to zero in the affected areas."

Just as an idea of a dedicated icon for false color function. :wink:

false color icon

Maybe this is not the best case, but for instance I set the false color (as LUT) to check the exposure of this image.

I set a mask to control the exposure incidence in the cloth.

Then I set the mask parameters an the exposure to tweak the pink color of he cloth.

Of course I know there are different ways to check the exposure without use the false color, and eyes and perception are the best tools, but this visual guide it will be great to use as another exposure indication.

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Ya I was suggesting to port this code as it basically did the same sort of thing using the L channel in a small preview which could be changed to false color and could be projected on the image…or if you had a false color option in the parametric mask… you could show it with the shortcut of holding the C key over the sliders to show that channel mapped on the image… right now that shows as white to black but could show as false color one would think with out too much tweaking…

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Ah, ok. This will be great, maybe the code can be configured this way. Other software like DaVinci goes a long way with this option to help visually impaired people, they can change the colors to their liking and as best can help them to visualize the false color.

Some samples screenshots with different colors combination:

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I still don’t see what a “false colour exposure indicator” would give us what the available tools don’t give us.
I’m not sure “nice to have” is sufficient reason to add yet another visualisation tool, with the same problems concerning sample location, colour spaces etc. we’ve seen with the existing tools for exposure and gamut verification.

Hello,
Personally, I find this a good idea. You could for example take the colors in the histogram of the tone equalizer, a bit like in ART.
Greetings from Brussels,
Christian

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Hi rvietor,
I would love to have a false color tool for checking exposure. It is a task that I am looking for pretty often to compare for example the exposure on the bright side of a face vs. the dark side of a face. This is something I am not able to do consistently with my eyes so false colors would be a great tool to help visualize something like this. I am even sometimes editing photos in Davinci mainly for this reason.
Daniel

whats the main difference to the mask preview in tone equalizer?

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tone equalizer changes the tonal values in an image based on a mask, that can represent 9 different levels. This mask can be defined so it covers the full or just a smaller a smaller range of tonal values and so gives you these 9 correction levels on a subset of the tonal range

image

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I wonder if the fact it’s greyscale makes it harder to visualize the separate zones? In very low contrast photos and very high contrast photos, it can sometimes be hard to distinguish between them all.

Would a false colour option in the Tone Equalizer module be of merit? I’m thinking this mask would show 9 different hues in the image, and which you could then easily map to the 9 adjustment levels in the module because each node would be coloured in the same hue…

The TE mask is not the image though so would that give what you want…you want to know some zonal information from that actual image data and not the mask or am I not correct??

The mask shows the zones to be modified, so it doesn’t need to show the underlying image in false colour. As long as the false colour maps to the actual nodes, it would be clear which node will act on which tonal area. So, the only change is that the mask shows false colour instead of greyscale.

I don’t know if it’s feasible. I’m just throwing it out there as a suggestion because the request for a false colour mask comes up fairly regularly. So I’m wondering if this is a solution.

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Somehow my interface looks totally different:


I would love to try this masking thing, then I could give you feedback if the greyscale thing works well for me.