Color correction of low-light video in Vegas 4

aboukirev wrote on 2/24/2003, 10:13 PM
I'm looking for general feedback on the topic, maybe some tips or what not.

Till recently I did little color correction in Vegas Video. Till a couple of days ago, when I decided to give Vegas 4 a chance on one of bad clips. Very dark footage with a definite color shift. I know, I should use proper lighting, etc. Just it's not always possible.

First thing to do is to apply Levels filter. But this time adjusting all channels simultaneously did not produce good enough result. So I had to work on each channel individually. There I discovered that in order to do that I had to add filter three times (R, G, B). No problem, switching between filters is no different from selecting in dropdown list. Plus I can turn off individual channel adjustments. But does not it add significant overhead of passing video buffer from filter to filter? Anyway, strange design, and very different from Color Curves (multiple channels in one filter).

Tweaking three channels by eye is futile exercise, I need numbers or some hard visual cues. So I open Histogram window (wonder, how would you use Levels in Vegas Video 3 where there is no histogram window), select Luminance, R, G, B. I can read offsets for headroom and footroom on each channel. Good. Back to Levels filter. Oops, here numbers are 0.0 to 1.0 (in Histogram 0 to 255). I can still do things with immediate visual feedback on Histogram window. But Levels filter definitely needs some improvements (like operating same units).

Ok, maybe I could do it with Color Curves? They are mapping input levels to output too. Plus you can remap midtones and even make mapping nonlinear. Not so fast. Again some numeric input and readings would be nice (in proper units).

So, it's a fair amount of guesswork and hence takes longer than it really should. After about half an hour it was pretty close to what I wanted.

Forgive me for mentioning Adobe Premiere here, using Levels filter in it I was able to quickly adjust all channels and get almost perfect result in under 2 minutes. No real real-time visual feedback there but having Levels controls and histogram in the same window is equivalent to numerically precise operations. And that's all that needed.

So, I'm looking for ways to achieve similar results in Vegas 4. Any advise on what I might be doing incorrectly?

Should I submit my suggestions about Levels and Color Curves to SoFo?

Alexei

Comments

BillyBoy wrote on 2/24/2003, 11:08 PM
Been there done that...

http://www.wideopenwest.com/%7Ewvg/tutorial-menu.htm
Paul_Holmes wrote on 2/24/2003, 11:09 PM
I have been using the new Color Correction filter in Vegas 4 and sometimes adding the Secondary Color Correction Filter, plus using a Color Curve Filter to sometimes flatten the contrast a little. I'm finding it a snap now (after some practice and still learning) to get fantastic results. I use the Vectorscope to keep my colors from getting too far out of balance and the Waveform to balance the luminance and gain. Your first stop should be Billy Boy's Tutorials. His latest tutorials will get you off to a flying start in Vegas 4 with Color Correction filters and scopes. I never found it this easy to get well-balanced colors in Vegas 3.
RichR wrote on 2/24/2003, 11:22 PM
I found using the RGB Parade in the scopes panel dropdown and color curves pretty efficient. View the Parade RGB values and adjust the proper color curve and you should be okay.
aboukirev wrote on 2/25/2003, 8:30 AM
Yeah, I've been to BillyBoy's tutorials. Thanks, BillyBoy! They are a good start. I'm trying to optimize color correction workflow.

Thanks for RGB parade idea, Rich. I can see how it will help me.

Paul, the new color correction tools a very good at fine-tuning relatively good video. I tried them on my low-light footage, and it's even harder to tweak with these than with plain Levels and Color Curves. After I do Levels and Curves, I'm going to compose blurred copy of clip (with proper opacity) to eliminate noise. Then it will be time for fine-tuning colors.

One more thing I noticed is that vectorscope is low on IQ ;-) What I mean is it does not have I-line (complementary to human flesh tones) and Q-line (orthogonal to I). I know the angles approximately. Unfortunately it's a guesswork again.

I think, I'll let SoFo know through product suggestions.

Alexei
Paul_Holmes wrote on 2/27/2003, 6:11 PM
Talking about bad video. I'm having to learn my ropes on some very uneven stuff taken by my brother in Paris with my old Optura Pi. It's the typical new videographer zoom-in, zoom-out, auto-exposure, poor low-light and pan and scan all over the place. (To his credit he got more stable about half-way into the 5 hours -- his daughter lectured him on more stable camera-work :)). Anyways, with the low light stuff I do a lot with the gamma and gain, keeping them at a pretty low level to keep the noise down, and color-curves to even out the lows and highs a little. Giving me a real workout and I'm learning with every session.
aboukirev wrote on 2/28/2003, 12:56 PM
Actually, after a lot more reading (highly recommend "Color Correction for Digital Video" from CMPBooks by Steve Hullfish and Jaime Fowler) and playing with Vegas tools, I think I grasped the concept. Just use as many monitoring tools (Vectorscope, Waveform, RGB Parade, Histogram) as possible - you may see hints on one of them and totally miss on others. So far, I was able to achieve best results with Color Curves and new 3-wheel Color Correction.

I even managed to correct human flesh tones. Just select a frame and mask out everything except face or naked arms or just hands. Black (masked out) part should map into center of vectorscope, flesh tones constitute a spike. Adjust colors so that spike is about 10 degrees counterclockwise from Red target. Don't worry about your masking black moving off center (it's not black color from your actual footage) but try to keep it close to center. Masking helps isolating color range.

Four days of tweaking various footage and I feel almost comfortable.

Numeric readings still would be helpful since it's hard to recognize slight color shift in shadows by eye. Not that such shift will be noticed by viewers but it's important for overall analysis of picture.

Theoretically it is possible to create a plugin that will display readings from colorpicker tool placed over preview window. Reading position of mouse, plugin should be able to get precise value from video buffer at the same position. Place that FX on event, and you get event colors. Place it on track, and you get track colors after opacity and transitions. Apply it to video output, and you have color reading for composed video. Should be a neat tool.

Alexei
BillyBoy wrote on 2/28/2003, 4:38 PM
If you want to go the extra mile you can apoximate what you had in mind now doing the following since for some odd reason version four doesn't include a eyedropper that provides read out of RGB Alpha values for the color wheels directly.

1. add a track above your main track, drop in white sold color from the media generations tab.

2. Either slide it away so it does NOT align with the portion of the video you want to sample or drop the opacity on its track to zero.

3. Move your cusor back to the portion of the video you want to sample.

4. Use the eyedropper in the solid color video generator to sample the RGB values in the preview window or the timeline.

They won't match anything in the color wheels, but at least you can get values and compare them to elsewhere in the video or another video on another track so you have some basis to adjust off of.

aboukirev wrote on 2/28/2003, 8:52 PM
Yep, that works. Requires click, not just hovering over the spot.
Interesting and sort of expected is unpredictable color combinations that I'm picking - my eyes definitely lie to me.
Overall, exactly what I wanted.

Thanks.
BillyBoy wrote on 2/28/2003, 9:33 PM
Your welcome. Would be nice if the eyedropper was more like in Photoshop where it updates RGB values in real time as your drag your cursor around. Oh well, better than nothing.
TorS wrote on 3/1/2003, 12:58 PM
One little (free) program that will do what you want is syspal.exe. You'll find it if you search at Google. If not, let me know, and I'll put it up somewhere, all 155 kB of it.
Tor