Davinci Resolve Color Correction - Tips for VHS transfers?

[ENunn]

i'm trying out color correction for my tape transfers in resolve again. i usually do levels adjustment in avisynth, but someone said i should try resolve for color correction. i still don't think i get it. so what i'm wanting is the darkest black to be black and the brightest parts to be bright without clipping. that's what i usually do in avisynth, but in resolve i'm just really confused about it.

for example on one tape i'm doing, i'm looking at the waveform, and whenever i find a spot where i can go all the way to 1023 without clipping (by increasing the gain), another spot clips, but only in the blues. i lower the gain, and then everything looks washed out. and when i lower the gain on the blue channel, the blues don't clip, but then everything else looks weird. it's like its not white balanced even though i white balanced.

no correction:


all gain channels adjusted at once:


all gain channels adjusted but only the blues are lowered so they won't clip:


is this something i should worry about? does anyone have any pointers on how to get this right?

[Sharc]

What's wrong with the first picture (no correction)? Nothing is clipped it seems ....
If you want to lower the darks try to lower the "lift" and "offset" (brightness) adjustments. (I am not really familiar with DaVinci though).
The second picture is definitely clipped (blue), and only reducing the blue (3rd picture) will unbalance the colors.
Sometimes one has to accept occasional clipping of one component (e.g. the blue in the sky) for VHS footage. Reducing the gain (contrast, saturation) too much may result in washed out pictures.

Maybe I am missing your point. I suggest to upload a snippet of your unprocessed capture so someone with DaVinci experience may take a look.

[ENunn]

What's wrong with the first picture (no correction)? Nothing is clipped it seems ....

it's the source tape, it's a little washed out.

If you want to lower the darks try to lower the "lift" and "offset" (brightness) adjustments. (I am not really familiar with DaVinci though).

that's what i've been doing and in that regard the darks look fine.

The second picture is definitely clipped (blue), and only reducing the blue (3rd picture) will unbalance the colors.
Sometimes one has to accept occasional clipping of one component (e.g. the blue in the sky) for VHS footage. Reducing the gain (contrast, saturation) too much may result in washed out pictures.

thats my concern. honestly looking at it now, i don't think it looks THAT bad with the blue channel lowered. it might be a little off white balance wise though, maybe?

raw:


"corrected":


raw:


"corrected":


not the same part of the tape but its just an example.

Maybe I am missing your point. I suggest to upload a snippet of your unprocessed capture so someone with DaVinci experience may take a look.

here you go. this has a good chunk of blue in it. i can send more if anyone needs it.

[Darryl In Canada]

Not sure if this will help or if you already know this, but if you click the original node and then from the menu click Color--Nodes--Add Splitter Combiner Node you can then correct each of the colors separately, or click the Auto button to auto adjust each color. The result can sometimes be better than doing an auto-correct for the three combined colors.

[ENunn]

Not sure if this will help or if you already know this, but if you click the original node and then from the menu click Color--Nodes--Add Splitter Combiner Node you can then correct each of the colors separately, or click the Auto button to auto adjust each color. The result can sometimes be better than doing an auto-correct for the three combined colors.

thanks! i checked it out and it seems to do the same as using a regular node and lowering the blue gain there. i did the auto corrector and it didn't really help with the clipping.

[Sharc]

here you go. this has a good chunk of blue in it. i can send more if anyone needs it.

This is not the best capture to begin with. What is your capture setup/capture card? Check your proc amp settings. The luma is too low for the brights, see the picture. Adjust contrast and brightness and maybe saturation of your capture device to fit the luma histogram.


[Attachment 88725 - Click to enlarge]

But anyway, it is not clipped, so you can do corrections to taste in post processing (Avisynth or your NLE) as long as you don't introduce (too much) clipping. In Avisynth you can try something like

colorYUV(gain_Y=100,off_Y=0,cont_y=50)

[Attachment 88726 - Click to enlarge]

Also you may want to apply different corrections per scene for this clip, I don't think the 'Blue' is your main/general issue. 'Colors' are also a matter of personal preference though.

[rgr]

it's the source tape, it's a little washed out.

I would only change the luma (in Avisynth) and leave the rest alone.
Something like that:

ConvertBits(10) # or 16
ApplyGradationCurves(lumapoints="16,16,160,235")