Colour matching to a known colour.

farss wrote on 4/8/2005, 5:57 PM
Boy does life throw me some curved balls!
What started out as a simple VHS to DVD job just got rather complicated. They want me to match the color of an item of clothing! Good news (or is it?) they still have the item but I don't have a DaVinci!
What I'm going to try is this, take a still of the item on my still camera using the flash so I know its daylight, bring that into Vegas and then using the scopes and CC match the two colours.
Anyone got any better ideas?
Perhaps I should firstly just CC the footage as per normal and then secondary CC to pick ou this one item and match that to the sample.
Bob.

[edit] Oh dear, now I'm looking at the footage and it's awefully dark as well. This is going to get very tricky, just dialing in enough gain to get the levels half decent isn't going to make matters any better.

Comments

Gonzoman wrote on 4/8/2005, 6:07 PM
MMMMMmmmmm - my thoughts......

No matter how much fine-tuning you do to match the color of the item, it's going to look different on different tv sets. Even if you match the color exactly and it looks great on your tv, it might be off-color on someone elses tv. I think educating the customer of how impossible it would be to match the color exactly and just doing your best to get it close will be your best bet.

Good luck!
johnmeyer wrote on 4/8/2005, 6:27 PM
I have tried this sort of thing before on stills, and it seldom works, even though you'd think it would. The problem is that the color is not just a hue, but an intensity as well, and the whole color balance shifts if you try to balance to a brighter or darker version of the "same color." At least Vegas has the Secondary Color Corrector, so you won't mess up the whole image if you don't get it quite right.

Too bad there isn't some sort of "color difference" mask; you could then line up the original video with the video or still you are using as a reference and then CC until the difference approaches zero.
Orcatek wrote on 4/8/2005, 7:11 PM
I've used color correctors primary and secondary.

One trick I like to use it to use the chromakey eyedropper tool with the FX turned off. It gives you the RGB values. I then work testing the two images back and forth to get them to be very close. I use the area selection in addition to the point selection method.

Of course as other have said different TV's will show the color different, and RGB is only one of many steps to getting it right.

You may want to look at some of the threads on matching two cameras, as that is very similar to what your trying to do.

Good luck, it's going to be fun - especially if the object is moving through various amounts of light over time. You have to pick the match time and let the rest vary or it will look really odd, more education for the client.
farss wrote on 4/8/2005, 7:12 PM
John,
I've now had a good look at the footage in Vegas and this seems impossible.
I can get everything else looking pretty much OK, the whites are white, blacks black and skin tones looking reasonable.
But the item in question is a fan made of PINK feathers. In the video the feathers have turned PURPLE! Secondary CC seems to be useless due to the huge range of luminance and the color shift in the feathers as they get waved around so I've scrapped the idea of getting an exact match. But even trying to shift the purple back to pink isn't working too well. I'm pretty certain this footage was shot under fluro lighting so there wasn't that much in the red channel to start with. I can sort of push the feathers to around the right color but then the rest of the frame is looking WAY off. I guess I can use a composite and track the item to sort of create a 'power window', but this is getting to be an aweful lot of work.
Actually even that could bring me unstuck. This was a "Pink Ball", all the ladies were wearing pink, so apart from the fan, in the other shots all what I assume were pink dresses are now purple, I'm sure as hell not going to spend a week masking every dress in 20 minutes of footage.

I think I'll just do the best I can and tell the client if he wants anymore I'll send it off to a grading facility. They could maybe ingest at 4:2:2 which will give them more data to work with, assuming there's actaully anything on the tape to start with. The amount of noise and very soft nature of this VHS is also not helping, this was shot 20 years ago on VHS in low light, the kind of stuff nightmares are made of.
Bob.
Spot|DSE wrote on 4/8/2005, 7:20 PM
Bob, can you apply a color mask to a dupe of that segment of the vid, then apply grotesque reds, and then use a compositing mode to blend them to the more accurate pink?

[edit] I couldn't find any purple feathers, but found a purple plant and made it pink. I sent the veg to the email you and I use to correspond. Lemme know if it helps at all?
BillyBoy wrote on 4/8/2005, 8:06 PM
Post a small sample of the SOURCE video before you messed with it or email it to me and I'll take a look when I get a chance.
farss wrote on 4/8/2005, 11:13 PM
BB and DSE thanks so much for all your help.
I'm pretty familiar with secondary CC and all the tricks. Problem basically is getting a clean mask, given that the source has chroma separation, noise and never gets over 50% luminance, trying to pull any sort of mask is impossible. If this was something half decent to start with I might be inclined to put more effort into it but me thinks this is like trying to turn water into wine, well outside my providence.

I'm doing pretty well with plain CC, I can get the offending colour looking a lot closer to the real thing without knocking the rest of the frame around too badly.

Just for a bit of education I tried combining bezier masking with secondary CC but even that is problematic, as this fan gets waved around and parts of it fall into shadow the SCC mask generator looses it.

One thing I need to understand better is the sequence of things in the stream and how to control that, I thing in the Two Cats .veg there was some hint about this, still haven't figured that bit out as yet. For example if you apply SCC and a mask there should be a way to take the output of the mask as the input of the SCC or the other way around. I think in broadcast parlace this is the difference between an upstream and downstream keyer.

Bob.
apit34356 wrote on 4/8/2005, 11:40 PM
farss, have you tried using the chroma blur, then cc with mask on the event? Since the object is moving, you'll be keying a lot of frames with different CC settings and probably BEZIER masks in some of the frames. Sometimes, a multi -track mask is require like when a multi-color light source passes over the "object" being masked for color corr..
farss wrote on 4/8/2005, 11:47 PM
Hm,
chroma blur is the one thing I haven't tried. Given the amount of chroma noise that'd be a good idea. I'm rendering it out now, I might go back and have another play with it. And this was going to be a quick job, ha.
Bob.
craftech wrote on 4/9/2005, 5:20 AM
Bob,
Color correct to get the pink looking as good as possible and leave the skintones off color. Dig out your commercial DVDs and have a look at some of the skintones on them. They are often way off. Many are sort of orange and some look sort of blue throughout the whole movie. I guarantee they wont care.
If pink was the theme, then THAT is what they are interested in seeing. Pink outfits. The skintones aren't going to bother them unless they are WAY off.

John
BillyBoy wrote on 4/9/2005, 7:24 AM
One last thing... When I have a harder color correction issue instead of messing with compositingor masks I use both CC and CCS. I agree with what John said. Decide what is more critical to the scene. If you push the skintones a tad off but get the pink feathers right, everyone probably will be happy.

What I do... Use color corrector first to get as close as you can. Now drop on the secondary filter. I've often found that in combination the ability to tweak in tiny steps to tougher shades of what you want is better than using either filter alone. Often, just a little nudge on the CC2 single color wheel, a minor adjustment to either saturation, gain or both in that filter will get you there.
vitalforce2 wrote on 4/9/2005, 12:49 PM
Or--you can eyedrop the color you want to match and then click on "color match"--oops--that's not Vegas 5. Maybe Vegas 6? Or 7?

(I sent in that product suggestion half a year ago. Cross your fingers.)
.
farss wrote on 4/9/2005, 2:07 PM
Thanks guys,
job is finished and looks well, just passable. All of these ideas are entirely valid but fail to take account of one fairly serious issue, noise. Now maybe I'm wrong saying this but here's what I'm seeing, all the color correction tools involve increasing the gain of a given channel, you want more red, crank up the gain on the red channel, simple, well OK it's a bit more complicated than that as it's a six vector CC tool, but that's a close enough analogy.
Problem with worn out VHS is it was pretty noisy to start with, then over time you loose the signal due to tape wear or partial erasure of the signal. So to deal with the overall loss of signal we dial in some gain, but you're only working with 8 bit values and on top of that there's all the noise on the tape. So just increasing the gain to get the levels to a reasonable state brings the noise up a lot, then using anything that adds gain in the color channels makes the noise worse as most of the noise in VHS is in the chroma signal.
Now the whole aim with this job was to transfer to DVD and the one thing that'll spin out a mpeg-2 encoder is noise, you end up with a noise pattern that's frozen during each GOP, very ugly in my opinion.
What I ended up doing was just using CC, pretty much to get the most noticable color looking better, needless to say the whites are a bit off but the eye compensates for that pretty well. Errors in the extreme colors seem to jar more.
So having got that under control I then used Mike's deNoise filter which did an excellent job. It obviously doesn't perfrom miracles, not with this amount of noise, but it did get rid of the noise in enough of the frame so that the encoder could cope. As expected the noise is still quite intense around the edges but again that's expected. I did also notice some ghosting from the filter but I don't think the average viewer is going to find that objectionable.
Bob.