Color correction card / Flat color profile interoperation

[Dimedrol]

Hello there!

I'm a newbie in video production (although, with some experience )
and definitely newbie in color grading.

My software: DaVinci Resolve 17.

ATM I'm curious on the following:

I have a video footage in flat (or e.g. LOG) color profile.
If I use color correction card,

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making my video,
should I use color conversion function, e.g. special LUT for transforming LOG to Rec709?
Or I can just match colors from the color correction card (and it will be enough) ?
(DaVinci Resolve can do it - select card and draw the rectangle above the card on video)

So if I have color correction card - do I still need "remove LOG" operation with special LUTs and/or software functions?

Another question, which follows previous one:

What if I have a footage, taken without LOG/Flat profile?
E.g. on smartphone (not FilMiC Pro or similar!) or old GoPro without ProTunes?
Can color correction card help me in adjusting (often, oversaturated colors on smartphones) stuff for my postprocessing?
Or, if I have smartphone footage - it is definitely unrecoverable garbage...?

Any ideas will be highly appreciated!

[Imamacuser]

If the footage is an actual log format, you should get pretty good result with a color space transform and tone-mapping. If it's a flat profile, you can look for a corresponding corrective LUT, just make sure that you apply the LUT to a node that follows your color and exposure tweaks.

If you get a Macbeth chart, make sure that it has patches which correspond with vectorscope colors, i.e. Rec.709 yellow, green, cyan, blue and magenta, along with patches for skin tones.

Resolve's auto correction off of a Macbeth chart may or may not give good results; you should still tweak the black and white point and might get more precise results with manual corrections in hue vs. hue, and hue vs. sat.

You could use a Macbeth chart to create your own LUTs for log or flat profiles. Since those profiles are intended for high contrast scenes, go out on a sunny day at noon, set your white balance to daylight, and shoot the Macbeth chart at correct exposure and also at +1 & +2 stops over to accommodate ETTR (expose to the right).

Low bit-depth and low bitrate cellphone footage has little to no wiggle room for correction, you might be able improve it a little, but don't expect miracles.

[Dimedrol]

Thanks, Imamacuser for explanation!
Anyway, as I understood, the practice is a key.