darktable: Style vs. LUT

Software darktable
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A darktable style can take full advantage of every module in darktable, but the style can’t be used in other applications.

A LUT is color, it is literally a “look up table” or a mapping of one particular value to another particular value (more or less) LUTs can be used in any application that supports the particular LUT format. It useful doing color grading and other artistic type of things. You won’t get things like local contrast or a low pass filter with a LUT though (like you can with a style).

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LUTs are made to a particular gamma/gamut, and if you use that LUT in a different gamma/gamut to the one intended/created you might get colour shifts. Further, in order to reduce file size, they use interpolation. If they have attempted large file size reduction by using fewer sample points (eg. 17x17x17 or less) you are more likely to see banding in smooth gradients. For most real world scenarios, ‘standard’ sampling of 33x33x33 will avoid banding, but no guarantee. (Darktable website says, “…that above 48x48x48 one cannot see the difference any more.”) More sampling points are better, but bigger files result. Interpolation algorithm will also play a part.

I haven’t used styles, but if they utilise darktable modules I doubt they require any interpolation, meaning no potential artefacts like banding (unless of course it uses an extreme adjustment which results in banding). But of course, unlike LUTs, they are limited to darktable.

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I am testing some LUTs. They show in the preview but not in the main editor in darkroom? Is that how it’s supposed to work? This said, they do show in the main screen while the display is on working.

Screenshot 2020-05-01 12.06.45
Screenshot 2020-05-01 12.06.451217×665 341 KB

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thats correct. It a set of ‚if this rgb value in source then put that rgb value in target‘ rules applied to each pixel.

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No, the result will be shown in the main window as well.
Do you have this problem with every LUT/CUBE?
(I am using dt git-version.)

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I tried a few LUT and they all not showing up. Tried on two PC so far Win10/3.0.2

I also checked some dtstyles, but IMHO they do often too many unwanted stuff.

This said, I found a cheap way for Orange & Teal:
Channel Mixer > Blue
Red -0.5
Green 1.50
Blue 0

Control intensity with uniform mask > opacity
Set blend mode to normal for, well, normal, and to hue for a strong effect.

I made presets for both.

Screenshot 2020-05-01 16.52.10

DSC04966_02
DSC04966_022000×1336 3.92 MB

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Downloaded LUTS work for me on dt3.0.2 running on W10. Although the only ones I have tested with are the freebies from ON1

Is your processor struggling that you ask about working being in the main window? You certainly wont see the effect until “working” is finished.

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No, I see the LUT effect ONLY when working shows, even when other modules process.

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Ahh got you… that’s weird… what LUTs are you using? Are they available online?

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I tried a few. All the same. You want more weird? Okay…

I mainly use darktable as a portable version on my USB drive, so I can move around without syncing anything. The LUT work on my laptop (i5, 8Gb RAM) but not on my desktop (i3, 16Gb). That the same USB drive, so it’s the same darktable folder/installation.

Do LUTs have a specific hardware requirement?

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Moin!
Please compare the output of the command

darktable-cmstest

from both machines.

Addendum 1: Ouch, sorry! That cmd does not exist on a Win machine.

Addendum 2: Does the command darktable-cltest show any differences?

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I can run darktable-cltest.exe - output is quite long. What you want me to look for? Just tried it on the working laptop. Will try the not working desktop tomorrow.

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It would be interesting to run a diff on them.
If you cannot do that in Win, send them to me, and I’ll check.

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Here are 4 files in 1 zip. “home” doesn’t work. “laptop” works.

I am already one step further. When I disable OpenCL on the home PC LUT is working. I think the issue is that the home PC has some OpenCL support issues. Graphic is onboard Intel 4400 which should support OpenCL 1.2

I probably need to update some drivers.

darktable.zip (24.6 KB)

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Splendid! It means that you are on to something :slight_smile:

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I have no idea what that something is though. Strange thing to me is that the CL output does not show any errors. All is loading fine.

One thing that puzzles me, there are lines for the portable drive like:

C:\Users\J_home\AppData\Local\Microsoft\Windows\INetCache\darktable\cached_kernels_for_IntelRHDGraphics4400_2019154835\rgblevels.cl.bin

I start darktable with: start /d "G:\Cam_Stuff\darktable\darktable302\bin" darktable302.exe --configdir G:\Cam_Stuff\darktable\darktable302\userdata\config

(I did rename the folders and main EXE not to meddle with the C: installed darktable)

And more thing, OpenCL seems to be used by many dt modules, but only LUT ain’t working? I don’t get that.

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If you close dt, get rid of all your cached CL kernels, then try again, what happens?

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I did rename the darktable folder:
C:\Users\J_home\AppData\Local\Microsoft\Windows\INetCache\darktable_old\

So no folder at all. dt takes a bit longer to load and to build a new cache, same problem. No change.

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They need to be in a specified folder …do your drive letters change when you move the USB??

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Sorry, what need to be in a specific folder? The Cache is located in INetCache, it got re-build after renaming.
But it seems that both the installed dt and the USB one use the same INetCache location.

I did set --cachedir for testing, also no change.