sQsA Darktable - short question / short answer

May I ask what OS you are running? I wanna get a RX480 myself but would love to stick with tumbleweed. I am not sure, if the AMDGPU-Pro driver (which is needed for openCL AFAIK) will do a good job on a rolling release…

I’m using Mint, never tried installing it on a different one, sorry. The AMDGPU-Pro installation goes smoothly, I just had to modify the install script to accept Mint instead of plain Ubuntu (change one string).

I’m using Manjaro. I have AMD A10 7870K Radeon 7 but cannot get opencl working. I’ve installed amdgpu and opencl-amd but as a newbie to Linux I’m not sure what to do next to get opencl working in darktable. Any ideas?

Might this link be of use to you?
https://wiki.tiker.net/OpenCLHowTo

Or this one?
https://wiki.archlinux.org/index.php/GPGPU

/Claes in Lund, Sweden

Thanks Claes - added to Pocket to read later.

I think this will not help. The opensource driver for AMD doesn’t include OpenCL Image support. So the only way to go is AMDGPU-Pro or fglrx (up to XOrg 1.17 if I remember correctly, fglrx doesn’t support any newer XOrg version.). But even if it would work I don’t know if it really would help as your CPU has a onboard graphics.

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Hi, what could have happened, if my historgram is gone? Thanks

That’s a strange one. When moving the mouse over the histogram, do you see the buttons for the color channels? Maybe you turned all of them off by accident?

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Maybe you placed a color picker on a dark (black) spot and activated the ‘restrict histogram to selection’ option in the color picker module?

Thanks @houz and @Wocket. I’m going to test it this evening.

Thanks

Ok, it really was like houz said… (sorry, that was stupid :slight_smile: )

Another thing. I’m trying to get into parametric masks. I created one, whiich should be limited to the dark areas. The mask, which I see suggests, that I have made everything correct (The drawn part of the mask is just for getting rid of a spot in the sky).
Here is the picture:

And here is the mask (so far so good :+1: )


No I do something a little bit extreme just to show, where my problem is. Here is what happens if I raise the exposure by +0,70 EV

And here is what happens, if I raise by 2 EV.

What goes wrong here? While raising the EV I clearly see that the formerly pushed area gets dark again and then the rest gets brightened up.

thanks

Edit: OK, it seems that limiting the output is part of the problem (No I do understand the different influence of input / output a little bit better). But shouldn’t everything gets brightened up to a specific amount (instead of getting darker again)?

edit again: grml, it seems that changing the EV changes the mask itself. Is that intended? Thanks

As you said yourself, this is because you have added a luminosity mask on the output values. This kind of a mask says Darktable to select pixels which their values AFTER processing the image (here, increasing the exposure) will be in the range you have specified. So, when you raise exposure by 0.7, the luminance values of the mountains AFTER applying +0.7 EV are still in the range you have specified for the output values. But when you raise exposure by 2, the luminance value of this area AFTER applying +2 EV gets brighter than the specified range of output values. Therefore, they would not be included in your mask anymore, as indicated in your last screenshot.

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OK thanks, not what I would have expected, but I get the idea behind it. :+1:

@msd explained it really good. The point to take away is: In almost all cases you want to use the input slider and leave the output slider alone. There might be exceptions to that rule, but I myself never encountered any. :slightly_smiling_face:

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Saw this on Reddit regarding a query on converting colour to black & white. I liked the reply so much I’ve copied it below;

–]drxg 3 points 14 days ago
Assuming you are using raw files…
Switch to using the color channels module. With the drop down (output) set to gray I find adjusting the green and red (leaving blue where it is) can vary and provide a satisfactory tonal output.
Same thing in gimp but this is waay better.
Do this before touching the levels or curves as it alters contrast.