@Pierre Do you have a color card??
@Pierre If you want to explore some of your images in DT for exposure then you can use the zone map of the zone module. If you do two things, first enable the zone module and then use the scroll wheel to decrease the zones to 5…that makes it easy to see middle grey. Then be sure you have a dymanic shortcut set up for exposure. typically so you can hold down the E key and use the scroll wheel to adjust exposure while the zone module is active that way its map updated and you can compare with the histogram but esp the zones …if you explore this for a number of your images you may come up with a value that typically sets them correctly for middle gray exposure or maybe even a little higher if you are using filmic…the zone module comes after filmic in the pipeline so if you have filmic applied then you would need to drag it before to assess exposure going in or you can leave it after and use it to assess it after filmic…its a crude thing and if you have a good eye you can use the color assessment background but my eye is not that good…I don’t do this as a rule when I edit or anything but you could try it as you work at establishing your workflow…
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Actually @priort, filmic always maps middle grey → middle grey, so if you are only looking for parts of the picture that are at 18% middle grey, it doesn’t matter if zones is before or after filmic. Of course, the other zones besides the middle one can be remapped by filmic, so if you want to look at those, you may want to put zones before filmic, depending what you want to look at.
Unfortunately, I don’t, and I’m not sure I’m willing to spend the money to get one just to setup one (old) device.
Whoo, that is a very interesting module, thanks!
For now I use the technique suggested by Aurélien, which is to activate the middle grey border for the image, zoom out, then adjust exposure so that the image looks adjusted to the middle grey border.
OK, I’ll do that then, I was just wondering if darktable was using some kind of database, similar to the lensfun database for automatic lens correction. If that was the case, there could be a better “default” exposure for a given brand/model, but as you mention it might depend a lot on the photograph being taken (subject, lighting conditions).
Pierre, could you please tell more about this? How do you “activate” the “middle grey border”, specifically. I have just started playing with the new (stabile) version and trying to understand it better.
A gray card use is not limited to calibrate a device once.
Even with a new camera, you could use it to set the exposure, but also to correct your white balance in some difficult scenes.
A useful tool to have in your photo bag.
It’s the color assessment tool (lightbulb button under the bottom right of the image):
https://elstoc.github.io/dtdocs/module-reference/utility-modules/darkroom/color-assessment/
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Thanks, Matt. Most helpful. I already knew that white border for color assesment but I was not aware that the grey background was a proper “mid gray”.
I understand the concept but I have tried this a bit and it doesn’t leave me confident that I am matching that tone at all…I mean perhaps as a rough guide. If I was comparing a monochrome image fine but in color images my brain does not connect the dots as it should I guess…
@Matt_Maguire Is that not the point of adding or subtracting exposure, ie to get part of your image into middle gray tones that you feel should be middle gray or have middle gray properly exposed?? Maybe those aren’t the same things?? Filmic unless you enable the middle gray control as you says uses a value or 18.45 for a central point and then the black and white are reeled in by adding EV to define the dynamic range mapping is that not correct?? Aren’t you defining what it uses or maps to 18.45 by adding or subtracting exposure… I guess you are saying that the middle gray going in to filmic is not changed just the mapping of black and white on either side so it won’t matter for the middle grey area shown in the zone map just how the other zones will shift after filmic black and white ev settings are applied ??
@Pierre its not perfect but you can use the test shots from here to try the various calibration appoaches. They have image pairs of test shots for a few iso with colorcharts. It won’t be as good as if you had a card but it does actually sometimes help with color Olympus E-M5 II Review - Thumbnails
Exactly right, Todd.
In the dark room (when you edit a picture), there is a light bulb icon at the bottom of the screen:
It’s the “ISO 12646 color assessment mode” that was apparently introduced in darktable 3.0.1. Click on it then zoom out, it should help your eyes to assess the levels of grey in your photo.
Hope this helps!
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Thanks, Pierre.
Judging colors on screen is almost a nightmare for me, especially at night. I can not even see the blue channel of the histogram. That mode is really helpful in this regard.
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I have looked through several tutorials on monitor color calibration. One thing is, the calibration is only valid for the ambient light conditions at the time the calibration is done. This implies that colors on the screen are different depending on the light in the room. Not a very comforting thought, but there it is.
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Isn’t it more that the colours on the screen appear different depending on the ambient light, because your brain tries to compensate based on ambient conditions?
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Very true! Now I process “relatively color-sensitive” images (a totally personal statement, not to be taken seriously!) always under similar lighting conditions. This means never finalizing those images at night.
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I suppose all color is a matter of perception.
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Slightly off-topic, but is there a way to do this without using the scroll wheel? It doesn’t seem to work for me, which I think is because I have “mouse wheel scrolls module side panel by default” enabled in the settings. But I can’t find a button or setting anywhere to do this without the scroll wheel. I have the same problem in the monochrome module where the scroll wheel is used to change the size of the filter.
What ever you set in preferences…ctrl alt scroll will give you the opposite…its like toggle…
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