Thread: Diving video
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Old 8th June 2018, 18:59   #56  |  Link
WorBry
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Join Date: Jan 2004
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Well curiosity got the better of me - I 'took the plunge' and signed-up for access to the 'video color correction' component of the Dive+ app. Don't have any other native under water clips, so I took samples from this YT video where the guy compared the original (ungraded) footage (shot on a GoPro) with corrections done in Final Cut Pro X

https://youtu.be/RTtS_baA5a8

Here are frame grabs from two of the original (ungraded) and graded segments. And the same corrected/graded with the Dive+ app and by me (as best) with Resolve.

Test #1:

Original:


Corrected FCPX:


Corrected Dive+:


Corrected Resolve:



Test#2


Original:


Corrected FCPX:


Corrected Dive+:


Corrected Resolve:


In short, I don't think Dive+ does a very good job. In these (and other samples from the same) it seems to arrive at an overly warmed balance with pretty poor exposure control. I think it just got lucky with that frame from your sample clip. Also it appears to grade each frame individually and there is a fair bit of fluctuation in the corrected outcomes within the same sequence - there's no option to select a representative frame for correction and apply to the entire clip. I'm not impressed.

That said, I'm not so impressed with the grading that was done there in Final Cut Pro X either. Seems to have fallen into the same trap I did when I first started playing with your sample clip in Resolve - thinking that if you push the color wheels (or whatever the equivalent tool is in FCPX) around enough and get the colored 'subjects of interest' to what they should be (or assumed/remembered to be), it will look good - or else 'better blue than green'.

I've come round to realizing that it is more important to get as close to neutral balance, as can be achieved, in the first instance. If it's done right, the true colors should more or less come through. Both grades I did there with Resolve adopted that strategy - balancing as best with the Channel mixer and then finer tuning with the color wheels. In hindsight, the first one (Test #1) could do with more work, especially that residual aquamarine tint on the sea bed, but I think the second is probably close to 'true'.

Also had a go at it with VirtualDub2, applying the same principle. Don't know what filters Shekh used specifically in the example he posted earlier. I've used:

*Channel Mixer (Emiliano Ferrari's version)
*Shekh's (Anton) very excellent '6-axis Color Correction' for secondary tuning.
*Levels and Gradation curves for levels and contrast (centre-relative)
*Unsharp Mask (Antons).

*Color Tools (1.4) scopes (Histogram, WFM, Vectorscope) for reference.

Two cracks at the Test#1 sample:



Bit more saturation of reds/orange:



Not bad for a first attempt....and possibly the most natural looking of them all - owing in part to partial desaturation of 'emerald' (one of the '6-axis' correction filter colors ) which targeted that 'aquamarine' tone on the sea bed very well. More tricky to treat that as cleanly in Resolve without ramifications.

Quite honestly Tormento, if you are not up for Resolve (which is a bit of a leaning curve), I'd have a look at VDub2. I could be wrong, but I think the chances of coming up with an AVS plugin for 'automated' underwater color correction are pretty remote. Closest I could imagine would be a Channel Mixer based function that maybe has generic presets for depleted channel reconstruction when there is blue or green bias, which can then be tweaked. There are just too many variables involved for automated correction IMHO and you're better off color correcting/grading on a case by case basis. With VDub2 you could also use Shekh's Master Blend filter for keying in subtle changes made with the 6-axis color correction filter.

In terms of 'free' software, there's also KDenLive, which I know is popular in the dive community, but I'm not sure if the Color Channel Mixer 'effect' has the secondary subchannels (RG, RB, BR, BG) where most of the work is done.
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Last edited by WorBry; 9th June 2018 at 14:08.
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