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Old 26th June 2018, 05:30   #13  |  Link
WorBry
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Join Date: Jan 2004
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Here's another version that (I think) achieves better balance on the 'cave' clip.



This used the same preliminary channel mix as Mix 1A (with the skylight for neutral balance) but I then used RGB curves to apply a progressive shift in the Blue/Red balance over the tonal curve to produce a warmer mix in the darker tones. In essence, it substitutes for what, in Resolve, could be (better) applied with the Primary Wheels or Bars (i.e. Lift, Gamma, Gain). I could probably manipulate the curves further to target that feint blue tint that is still coming through on the Sergeant Major fish, but it's very finicky. The curves tool in Resolve has a nice feature where samples taken off the image are marked by the component values on the RGB curves, making it easier to target and manipulate specific colors. Still the VDub2 result is better than it was and it holds up pretty well throughout the clip.

Untested as yet, but I'm sure the same can be done in AVISynth with RGBAdapt.

The settings are the same as those I posted for Mix 1A above, but with the addition of RGB gradation curves, placed between 'Levels' and 'Unsharp Mask 'in the filter sequence. The R and B curve coordinates were:

Mode: RGB Adjusted + R/G/B

Red Channel:
In/Out
0,6
255,255

Blue Channel:
In/Out
23,0
255,255

Simple as that, just linear shifts in the R and B curve gradients.

Moving on to the remaining two test clips, similar considerations apply to GOPR0201 where we again have patches of skylight flooding in from above. Like the 'cave' clip, it makes sense to use the skylight as a reference for the channel mix (especially as there is a paucity of other neutral subject matter) but with the inevitable consequence that colored objects at lower depths are blighted with blue/magenta casts and under-representation of reds/yellows, resulting in washed-out, off colors - that yellow (ochre) coral bed in GOPR0201 being a prime example. Tweaking the channel mix at best achieves a mediocre and unsatisfying compromise.

So far I've managed to come up with some quite nice grades in Resolve using the Channel Mixer and Primary Color wheels, coupled with 'soft-clips' applied to the individual RGB channels for fine tuning of the highlights and shadows - and without recourse to 'qualifiers'. The tricky part is now translating those manipulations into RGB curve representations that can be applied in VDub2 and in a way that produces a smooth transition of hues in the sea background.

This type of scenario is where a 3-way version of the '6-axis color corrector' would come in very handy (hint, hint).

I'll post some results when I'm done, but will be going on vacation myself next week.
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Last edited by WorBry; 26th June 2018 at 05:52.
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