Quantcast Color correction for VHS captured videos? - digitalFAQ Forum
  #1  
06-24-2020, 03:29 PM
Okiba Okiba is offline
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Hi everyone,

I would like to start correcting Color in my Captures VHS videos. Everything appears a bit too "Red" for my taste. But that's just my taste, and that leads me to the questions:

Is there's a "Right" absolute way to correct colors? Or it's really up on the person who Convert the VHS because different people will have different opinions on what "good colors" would be?

And if indeed there's a "Correct" colors, is there any tools that help you calibrate it correctly? or it's just years of experience? It's seems there so many options (from the basis like Brightness/Contract, to the more advanced stuff like Saturation and hue, up to Gradation Curve). Is there any guide I can follow to give me some basics? And lastly - let's say I did "Corrected" the colors. Can I use the same settings for all the videos (as I current the "specific hardware" I'm using) - or it also very much depends on the content type itself?

Thanks!
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  #2  
06-24-2020, 08:28 PM
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jwillis84 jwillis84 is offline
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The nature of the color video signal is that absolute colors are separated by a Phase offset from a color burst reference Phase.

All of the colors are strategically placed so they are always the same distance from each other, a color error in transmission or reproduction generally rotates all of them around a Phase angle from 0 to 360 degress, like on a dial.

So the Hue knob on a processing amplifier can turn Left or Right, and "push" the Phase of all the colors one direction or the other.

Doing it "by eye" you usually try to pick a single color and focus on adjusting all the colors at the same time by getting that one color "correct". Some people pick "blue" other people pick "white" and do a white-balance.

You can also use a signal generator to correct your monitor or tv "first" and then correct the incoming signal by deliberately skewing the hue so it looks correct on the display.

To do it by taking the human element out of it, you need a vectorscope.. which takes each scan line apart and displays them radially around in a circle on basically a "polar" plot. The distance from the center to the edge of the circle is saturation, but the colors are displayed around the center axis.. and fall in "guide boxes". When your looking at a test pattern of color bars they end up as bright spots in the boxes.. and you know they are correct.. if they are off.. you adjust the Hue knob back and forth, Left and Right until they are lined up in the boxes.

Imperfections that are part of the color error when the signal is generated at the studio where the camera films or shoots are more difficult to correct. Correcting one color axis at a time is more akin to timing or "coloring" by adjusting one color at a time.. which is beyond what most people can do at home.

Colors generally all rotate or "err" together in synchrony.. so adjusting them corrects them all at once witha single twist of the Hue dial.

Errors that are within a single scan line or that differ from line to line are termed "color noise" and don't last long enough to correct. Filters are used for high frequency or low frequency color noise.. but usually soften or reduce the resolution of the color information in the image.

Luma or (monochrome) picture information is transmitted at a finer detail or resolution than color information.. so color noise is generally less of a concern to most people.. or goes unnoticed.

Last edited by jwillis84; 06-24-2020 at 08:45 PM.
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  #3  
06-24-2020, 09:55 PM
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lordsmurf lordsmurf is offline
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That's a terrible thread title. Fixed.

Step 1: Is your monitor calibrated? Otherwise you'll make colors worse, not better.

Science only goes so far, and color grading is an art. But the base science is to use histograms and graphs, and the eyeball tweak after you know the true values. If the value disagrees with the monitor, the monitor is always wrong.

Sometimes Avisynth is best.
Sometimes VirtualDub's ColorMill is best.
Sometimes Premiere.
And after having used DaVinci, it's decent, but not really as magic as some folks think it is.

All videos are different. Even scenes within the same video is often different.

Video takes times, if done correctly, there is no easy button. At least with capture, the hardware was the bottleneck, and settings, usually fairly painless afterwards. But with color correction, the learning curve is steep.

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  #4  
06-25-2020, 02:25 AM
Okiba Okiba is offline
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Quote:
That's a terrible thread title. Fixed.
Yea, It started as a topic about color correction but became something more general when I started writing it. Thanks.

Thank you for the technical explanation jwillis84. It never stop to amaze me how much there is to know about Video.

Quote:
Some people pick "blue" other people pick "white" and do a white-balance.
When you try to adjust black/white levels so they won't clip. You don't actually do a "White-balance" right?

Quote:
Step 1: Is your monitor calibrated? Otherwise you'll make colors worse, not better.
On some level. It's never done professionally with external device, but I have been using AVSHD. I'm not sure how accurate it is.

Quote:
Science only goes so far, and color grading is an art. But the base science is to use histograms and graphs, and the eyeball tweak after you know the true values. If the value disagrees with the monitor, the monitor is always wrong.
So a good start will be trusting histrogram and graphs over my eye because I'm not sure how good the Monitor is? Is there any good starting point about how to use graphs/histogram?

Also, when the color tweaking have to happen? Setting it up before the Capture so it will be captured correctly? Post capture in the Loseless Digital format? I probably won't be able to keep all my videos on Loseless format. Does changing Colors later on on a Lossy compression is really bad idea?

Thank you both!
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  #5  
06-25-2020, 08:18 AM
themaster1 themaster1 is offline
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You can do it during the capture with a calibrated monitor i guess, but generally you do it post cap.
If you capture lossless in YUY2, no problem for colors / quality, in YV12 -> problems.

Try sony Vegas if you can it has great video scopes (histogram etc..) very intuitive
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  #6  
06-27-2020, 11:29 AM
Okiba Okiba is offline
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So Post Capture is fine. And when you say YV12 you mean lossy format?
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  #7  
06-28-2020, 03:30 PM
themaster1 themaster1 is offline
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i mean color space, yv12 (4.2.0) is less qualitative for color correction. YUY2 (4.2.2) is just fine, YV24 (4.4.4) is overkill for vhs
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  #8  
06-29-2020, 02:15 AM
Okiba Okiba is offline
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Oh. It's Indeed 4.2.2. What I wondered about is if I can do color correction on the Lossy MPEG format. Or I need to do all color correction on the Loseless Hufyuv format.
Basically I will do some correction now, but in case In the future I will find a more precise way doing so - I wonder If I need to re-capture from source (because I don't save Loseless files - too big).
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  #9  
06-29-2020, 07:29 AM
Hushpower Hushpower is offline
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Quote:
What I wondered about is if I can do color correction on the Lossy MPEG format.
Yes, absolutely. I am working on some MPEG files I captured from VHS 10 years ago; colour correction is easy (I am using some Virtual Dub filters). I don't know what I am doing compared to the experts here but the results are great for me.

At the time I captured these, hard drives were too expensive to fit all my DV files and I didn't really understand MP4 (or have any practical way to convert into), so MPEG 2 was the optimum format then, but it is lossy.

I am now re-capturing my remaining VHS tapes using Lagarith; 30gb per hour. Hard drives are now cheap, and I am going to keep my Lagarith files as masters for as long as needed. You could fit 100 hours onto one 3tb drive. Have another two for backups, and you have a lossless digital solution for the future.
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  #10  
06-29-2020, 08:08 AM
Okiba Okiba is offline
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Oh, great - Thanks! I's there anything I should be doing NOW on the Hufyuv format before converting it to MPEG2 as it's just not possible/will degrade quality later on Lossy format?
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  #11  
06-29-2020, 08:31 AM
Hushpower Hushpower is offline
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Let me re-phrase what I said: you can colour-correct MPEG (the experts here will have more to say about that) but my understanding is that working with MPEG as a source/master is not desirable.

I would strongly suggest you capture using Huff and store it that way for later, for when, using your words "but in case In the future I will find a more precise way doing so". I'm using Lagarith as the files are a bit smaller.

You might have to buy another/bigger hard drives. The alternative is to try to re-capture in say 10 years and find your VCR has stopped working (or your capture device has stopped working due to drivers becoming out-dated [if you don't have a Windows XP machine]).
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  #12  
06-30-2020, 12:48 AM
Okiba Okiba is offline
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Oh. Thank you for clearing it out. I have 10 years of Video Footage, so I'm not sure even 3T will be enough. Not to mention that 3T of information, need to get backup in-case of hard-drive failure. So I'm not sure I can get that many space. But it's indeed something to consider. Thank you Hushpower!
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  #13  
07-06-2020, 07:23 AM
sanlyn sanlyn is offline
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You need to learn basic color theory or you'll nd up with the usual crap. For instance do you know how to use RBG to make white? Photoshop and the Adobe Pro websites have free tutorials all over the internet. You cn learn a lot about color just by using histograms, which are similar for digital cameras and digital video color correction software alike. Try https://www.cambridgeincolour.com/tu...istograms2.htm

Red is corrected by reducing red or increasing its opposite color. The color that is opposite to red is cyan (Green + blue). Without basic color knowledge and histograms you're up the creek.
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  #14  
07-07-2020, 01:42 AM
Okiba Okiba is offline
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Thank you for sharing this link. I actually an amateur photographer - so this will be useful on that department too!

-- merged --

For future people who might stumble on this post:

Encoding from Huffyuv?

This has great information by sanlyn about colors/histograms etc.
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  #15  
07-19-2020, 11:34 PM
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lordsmurf lordsmurf is offline
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Quote:
Originally Posted by Okiba View Post
This has great information by sanlyn
Yes, he has some real gems of posts. Hopefully he's doing well in COVID times, he doesn't post much lately. I wish him well, hope to see him around more often again.

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  #16  
07-20-2020, 02:27 AM
Okiba Okiba is offline
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I hope so too! And hopefully, this will end soon.
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