Colour correction on DV Captures

[Imy]

Hi,

I recently captured some video from some NTSC DV tapes. The issue I have is that the colour looks too pale. I've tried doing some colour correction using VirtualDub however it is quite subjective and I'm concerned that I'm using the wrong settings altogether. I'm unsure whether its, the colour, gamma, luminence, chroma that needs adjusting.

I have a few questions:

1) Is there an analysis tool or filter I can use to identify colour issues on a histogram or something which will help guide me on what needs correcting?

2) Similar question to above but can I use photoshop to identify colour issues and export a settings file from there to import into a video editing tool?

3) My monitor is calibrated however how do I use the colour bars to correct the picture/colour of the sample footage?

4) I have the sample footage taken from an alternative source where the colours look fine. Is there a tool that I can use which does a like for like comparison and offers some recommended colour correction settings?

5) Can someone download the video files please and off some recommended settings to use in Virtualdub (or AVIsynth if I have to) to correc the colour?

Any help would be greatly appreciated.

Here are some video uploads I've done:

DV NTSC Tape Colour Bars at start - http://imyashy4.webspace.virginmedia.com/cbars.avi
Sample footage from Tape - http://imyashy4.webspace.virginmedia.com/Video%202.avi

The first pic is frame 488 from the source file. The Second pic is the same frame from an alternative version of the same video.

[themaster1]

a slight change of the hue should be more than enough, generally a +/- 7 do it for such video source

AVISource("Video 2.avi")
assumebff()
tweak(hue=7,coring=false)

if you want more saturation on the V component (reds/greens):

AVISource("Video 2.avi")
assumebff()
tweak(hue=7,coring=false)
coloryuv(cont_v=26)

[lordsmurf]

The second image is overdone, and now has too much red.

[jagabo]

Using a frame late in the cbars video (after the brightness stabilized):



I came up with this adjustment in AviSynth:

Tweak(cont=1.13, bright=-17, hue=2, sat=1.09, coring=false)



Applying that adjustment to video 2.avi gives:



That looks a little over saturated to me but that may be from some auto image processing in the capture chain.

I used this script with the cbars video:

AviSource("D:\Downloads\cbars.avi") 
Tweak(cont=1.13, bright=-17, hue=2, sat=1.09, coring=false)
VideoScope("both", true, "UV", "Y", "UV")

ovr=ImageSource("vectorscope overlay.png")
Overlay(last, ovr, width-256, height-256, ovr)

The last two lines are to overlay the colorbars target boxes using this image:

[LMotlow]

Why do people insist on using those colorbars for video color correction?

[jagabo]

They're only useful if the recorded video was accurate to start with.

[LMotlow]

Thanks for answering. Those types of colorbars are not used for video color correction, whether the video content is correct or not. As is, the video itself is mostly in the neighborhood of believable and you gotta remember that music videos go for lots of special effects and primary school color-- most ain't supposed to look that "real" in the first place. More relevant, every one of those has a slight but visibly different color cast and gamma level, so correcting for that one shot throws the rest out of whack. Brights in the original are blown to hell, but sometimes the TV crowd likes it.

Why is that video so soft?

[jagabo]

Thanks for answering. But SMPTE color bars are not used for video color correction, whether the video content is correct or not. As it is the video itself is mostly in the neighborhood of believable and you gotta remember that music videos go for lots of special effects -- most of 'em ain't supposed to look "real" in the first place. More relevant, every one of those has a slight but visibly different color cast and gamma level, so correcting for that one shot puts the rest out of whack. Brights in the original are blown to hell, but sometimes the TV crowd likes it.

Why is that video so soft?

The point of colorbars isn't to restore the video to its "natural" colors, it's to compensate for color and level shifts in an analog/capture chain. Otherwise nobody knows what colors anything was supposed to be and all color "correction" is arbitrary.

[LMotlow]

Yep. That's the usual answer. Colorbars are still ignored for that kind of correction. But I won't argue with the Absolute and Irrefutable crew here. What happened to the blacks in the pluge?

[jagabo]

The pluge blacks are all there in both colorbar images I posted.

[Cornucopia]

Yep. That's the usual answer. Colorbars are still ignored for that kind of correction. But I won't argue with the Absolute and Irrefutable crew here. What happened to the blacks in the pluge?

No they aren't ignored (by professionals).
Which is why pros keep colorbars & tone at the beginning of all the master tapes/discs/clips they make - it's a very quick way to restore to the original intent (of course, you have to marry proper bars to the content at the time the intent is "baked in"*). Notice: original intent, not "natural".
Way back when I did mass production of VHS at Allied/Vaughn (over 800VHS dubbing simultaneously, round the clock), it was a measure of your mettle as to how quickly you could properly set up a master to correct colorbars. I usually did in in 10-15seconds.

Just because things are now all-digital doesn't forego the need for a proper "reference".

Scott

*It's possible to add it in later, but that requires some artistic discretion.

[Imy]

The second image is overdone, and now has too much red.

@themaster1 @jagabo

I've attached a screenshot of the same video and frame from another alternative source. Will this help you in identifying some suitable settings to use after comparing to the original picture (frame 488) from the original post?

[jagabo]

If you just want to match colors to your alternate images, this comes close the second image in your first post.

Tweak(cont=1.02, bright=-14, hue=15)

The major change is the hue.