Lens correction with Leica Q2 Monochrom

Software darktable
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I’m currently a Mac/Lightroom/Capture One user working toward a full-time move to Linux. My photo workflow is a critical component, so the past few days learning my way around Darktable has been quite an adventure! I must admit I kind of hated it at first, but now I’m feeling much more comfortable and can even see a path toward preferring it.

However, I shoot mostly with either a Leica Q2 Monocrom or an SL2-S, neither of which appear to have available lens corrections. The Q2M really needs corrections.

What I’ve been doing is selecting the normal Q2 and Summilux combination, which, at first glance, seems to work, even though the UI complains that “Camera/lens not found!”. I’ve not done any serious comparisons, but I’m guessing this is my best option.

I suppose I’m just looking for a nod that this is workable, or what my options might be, otherwise.

Thanks

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You can tweak the xml-files from lensfun to handle the Q2M as a Q2 by simply changing the file “compact-leica.xml” in the directory \darktable\share\lensfun\version_1. Here, you copy the block

<camera> <maker>Leica Camera AG</maker> <model>LEICA Q2</model> <mount>LeicaQ2</mount> <cropfactor>1</cropfactor> </camera>

and insert it again directly after the block. Change the line <model>LEICA Q2</model> to <model>LEICA Q2M</model> or whatever the identifier of the Q2M is. Restart dt and the Q2M should be recognized by lensfun as Q2.

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The best way is to shoot the photos needed to make a correction profile for the lenses you have: PIXLS.US - Create lens calibration data for lensfun

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You happy one :slight_smile: The lens is the same as for the Q2 (i am using) so you can use that without significant problems. Unfortunately there will be (very small) problems due to the way the lensfun library handles colors.

I prepared a pr for that a while ago, good to remind me of that.

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Can you explain what issues it has?

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Interesting. I had no idea. I’ll take a look at that, thanks.

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I’ll do that, thanks.

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@carvac In dt monochromes have all channels set to same value. Lens distortion calculates with slightly different data for every photosite leading to minimal colorizing at sharp edges. I observed that while i was testing some Q2M images.

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Oh maybe this is what’s giving me interesting color noise in my infrared images.

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Care to upload such a shot to raw.pixls.us?

I have some M Monochrom samples but none with identifiable lenses with distortion correction.

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I don’t own any images, took from Leica Q2 Monochrom sample gallery: Digital Photography Review for testing

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@jbaty there is a prepared fix for darktable monochrome lens correction, let’s hope it will be in 3.8.1 :slight_smile:

BTW, i don’t know if you know about darktable presets already but i makes a lot of sense for the Q2 to apply a lens correction automatically.
Bildschirmfoto von 2022-02-04 06-21-31

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Yes, that helped once I found it, thanks.

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Good.

One more; i an currently working on an “improve the darktable monochrome workflow” project, if you have anything special, let me know.

Also - there are only few leica lenses in the lensfun database, it would be very good if you could contribute :slight_smile:

2 Likes