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steveseguin / color-grading

Automatic LUT creator for OBS using Color Reference Cards for Calibration
GNU General Public License v3.0
97 stars 11 forks source link

I made something wrong, but not sure where. #3

Closed j2l closed 1 year ago

j2l commented 1 year ago

Fantastic project to learn calibration @steveseguin, thank you!

I have a color reference card with known RGB values so I need exactly this project to make a correction LUT in OBS. I shot a full size ref card with some slight perspective and it also have numbers. Maybe because of this, it doesn't see the first colors and I get more RGB values in histogram and computed LUT is incorrect .

Is there a way, in Step 4, to see/tweak which point/area it "sees" (uses)? Here are my files enclosed to get an idea. wrong_card wrong_rgb expected: expected

ref card ref_card_int wrong wrong_lut

j2l commented 1 year ago

I corrected the perspective and it keeps on wrongly interpreting the same colors (first 4 and first 3 greys). ref_card_int(1)

j2l commented 1 year ago

cropping more and saving as JPG seems to fix it for colors: ref_card_int interpreted as: interpreted

But since color cards are usually with borders, a way to see/select areas is still needed (area to average noise, especially in low light). Too bad I can't code in python, I'd love to improve it with an array of rectangle you could move manually.

BTW, it should be mandatory to upload a photo taken at the same moment to test the correction instead of using your pic since your camera and light condition is different from mine :)

steveseguin commented 1 year ago

Thank you for the feedback. I can probably make a mode for color-cards that accounts for borders, or a way to select the points. It might be easier for me to make that in Javascript, to pre-process the image, rather than in Python though.

BTW, it should be mandatory to upload a photo taken at the same moment to test the correction instead of using your pic since your camera and light condition is different from mine :)

Yeah, definitely don't use my image if using your own color cards - that wouldn't make any sense.

steveseguin commented 1 year ago

I modified it a bit, adding a border-value option now. I have it pre-set to 25%, which should help I think in your case.

I also ran script with my own color card, and it turned out pretty okay: https://github.com/steveseguin/color-grading/blob/master/spyder_24_color_card.ipynb

image

image

If there's still an issue with noise, I suppose I can add a denoiser , but a blur filter might also work.

j2l commented 1 year ago

Great! Thank you @steveseguin !! Funny, looks like we have a mirror of each color card.

Your camera looks far better than mine though, histogram doesn't have more than the 3 RGB values, like I do. Since I have this "noise" value on the left side, and it changed after i cropped, I guess I would need blur. I could add it when fixing the perspective.

I'll test it tomorrow, thank you again!

steveseguin commented 1 year ago

I bought my card directly from Datacolor; wasn't cheap of course, but since I bought it as a replacement card (without case), it was reasonable.

j2l commented 1 year ago

Histogram is now far better. good_histogram It works fine, so I'm closing this ticket.

Thank you again for the fix and the overall quality of this project. It encourages me to get a decent camera :smile: