Current Server Time: 08:38 (Central Europe)

#apertus IRC Channel Logs

2022/10/24

Timezone: UTC


08:58
polyrhythm
We have an email thread going but here is the latest on color calibration...:
08:58
polyrhythm
we're close.
08:58
polyrhythm
https://i.imgur.com/6UCpRhY.png
08:58
polyrhythm
A pretty crude color match from Resolve indicates we're in the ballpark, even with the bare minimum 6500K calibration I did just now
08:58
polyrhythm
The cyan is pretty far off at 13% but everything else seems pretty acceptable
09:00
polyrhythm
this is really not going to be perfect anyway with just a 3x3 matrix, so thos numbers are pretty good.
09:00
polyrhythm
the next steps would be solving some of the issues with our current photos, getting spec-compliant raw2dng, trying out the IT8 chart to see how it fares with calibration, etc
09:00
polyrhythm
overall I'm pleased with the initial attempt
09:01
polyrhythm
most crucially, it looks like we achieved a good neutral calibration with no real twisted hues or garbage like that, just some saturation/luminance diffs. very easy to work with
09:51
se6astian
great, thanks for the updated
09:55
polyrhythm
oh and I just noticed I used the "Legacy" option for the color chart in Resolve, whereas the correct version is the non-legacy option, so maybe I'll try again later and see if it improves the cyan matching
11:32
vup
polyrhythm: what does the percentage in the resolve color match thingy mean?
11:50
BAndiT1983
maybe deviation
11:53
vup
yeah, but under what measure?
12:09
BAndiT1983
as i've missed majority of discussions, am not that deep into what was targetted, what would be the measure in this case? am seeing the x-rite classic (legacy) color chart and the deviation after correction
12:10
BAndiT1983
or ist it about the auto values there?
12:16
vup
BAndiT1983: no I think you have all the details. But with measure I mean you have a triplet of correct (X, Y, Z) values for the color checkers patches and a triplet of the (X, Y, Z) values the camera gives. How do you now combine / compare these two triplets to get a single percentage difference?
12:21
BAndiT1983
from my very basic knowledge it's just known values for the color chart and then the matrix for the conversion, the values are compared after applying the matrix, that would be it, in my understanding, this is where i miss a chunk of infos probably and have to look through the meeting notes, when my personal things are sorted out after this week
12:23
BAndiT1983
am refering to something like this -> https://www.imatest.com/docs/colormatrix/ and from trials with display calibration
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13:34
vup
BAndiT1983: yes of course, but how "exactly" are they compared
13:34
vup
hmm the light used seems to have different angular dependencies for different frequency components: https://f.coroot.de/cmv12k_color_response/greycard_zoomed.pdf
13:35
BAndiT1983
interesting
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16:00
se6astian
MEETING TIME, who is here?
16:02
se6astian
BAndiT1983 messaged me is is currently away but he reported he is still working on panel creation outline tuning, here is a work in progress screenshot
16:02
se6astian
https://i2.paste.pics/9084733a3ac09256e71ee6b1f8effc8f.png
16:05
se6astian
there is quite a lot going on in the color characterization front, but maybe someone wants to talk about it who is directly involved?
16:08
se6astian
anyone else around who wants to report/share?
16:11
se6astian
ok then, MEETING CONCLUDED
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20:19
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22:10
anuejn
this looks like some pretty nice hardware as an axiom-remote interim: https://carthing.spotify.com
22:10
anuejn
also it is easy to run custom code (web stuff) on it: https://carthing.spotify.com
22:11
anuejn
which would mean that it cauld be a low-effort solution for controling the axiom in the short term :)
22:12
anuejn
though sadly it is not very available in europe :(
23:17
polyrhythm
vup: The percentage means the DeltaE between the final matched color and the reference value of the patch. In this case, my test was to take the calibrated camera into Resolve and see how easily it could match the image, with the logic that a calibrated image is closer to baseline than an uncalibrated one and thus easier to match. It's a little misleading because I'm implying that my footage directly is those values; it's just the result after I let
23:17
polyrhythm
Resolve have a go at the calibrated image. The reason is that imaging pipelines throw the DNG into different provessing color spaces, so obtaining some kind of absolute DeltaE between reference patch values and the color chart photo is not super useful unless you know every step the processing software is doing when it renders the image from a DNG -> sRGB display
23:19
polyrhythm
in other words, I don't think there's value in taking a calibrated DNG, putting it into Nuke or Resolve or whatever, and just checking the DeltaE directly with reference values, because those software are going to process the DNG differently and put them into different working spaces to render them. I guess Nuke is the most explicit in this case in what is happening
23:20
polyrhythm
as best as I can tell, the calibration can be considered successful is we get ballpark correct images from the DNGs using minimal processing to a display transform and without hue twisting or significant saturation and luminance deltas