How should the SMPTE color bars be used on VHS?
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For the first time I've been given a tape that the dub house put SMPTE color bars and tone on before the main material during the original transfer. My question is for the experienced hands at analyzing these. How good could or should they be when capturing from a VHS source? What would you correct with them in AviSynth before going to the program portion for filter corrections? Captured with JVC HR-s7800U with TBC/NR on --> Datavision TBC-4000 --> Diamond VC500 via S-Video cables.
Erich |
More often than not, I find that color bars were just the byproduct of equipment used in the initial dubbing/recording setup, and not something by which the content was calibrated against. The inclusion wasn't intentional, and is in fact just lazy use of the gear, not turning off pattern generators (when available). I almost always disregard those.
Those bars in your example have a lot of chroma noise. Check if line TBC engaged, consider enabling the VCR NR filters as well (picture mode = NORM/AUTO) Also check s-video cables. |
This tape was recorded by the post house who did the editing/color corrections, so I'm hoping the bars are meaningful with regard to the content, but of course since it was over 20 years ago I have no way of knowing. As I said in the post, that capture already has the VCR line TBC and NR turned on as well as going thru the TBC-4000. I also have a number of different s-video cables I've tried, but that's pretty typical of the captures I've always gotten since I bought the units from you.
What would you suggest? Do I have a problem I need to take care of? Erich |
I would probably still disregard it.
Analog-domain correction was never precise, and is quaint compared to modern NLEs. Sure, if you really want to fiddle with proc amp controls, you can attempt to capture it perfect(ish) to the pattern. But I still bet the content isn't really that perfectly graded. |
OK, so in that case even if the grading of the pattern and the show are not related, is the chroma noise you're seeing still a problem? I've been going under the assumption that what I've been getting is normal since I've seen it since the beginning with this gear.
Erich |
All tapes have chroma noise, inherent to the format. Still images can make it look worse than actuality. Just attach a small clip, and converted to 4:2:2 H.264 would be easier (smaller size, I can view that on my non-video systems for quicker response).
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The attached clip in the first post is a direct stream HuffYUV copy. I'll post an h264 version tomorrow. This is the first time I've seen you ask for a processed version. :)
Thanks, Erich |
If you think the color bars on VHS tapes will make it easier to get good color and help you avoid learning about color, forget it. A proc amp won't help much, either, since your novice color skills are assuming that you can correct red, green, and blue (you can't. Correction in YUV is very difficult and clumsy) -- and what do you do when every scene in your VHS changes color balance and luma range? Do you stop the capture every 30 seconds to reset your proc amp? No way.
There's no replacement for understanding color theory and principles, and no push-button killer software that does it for you. Go to your nearest movie theater, watch old and new color work, and see what real-world results the pro's get. Stay away from YouTube (haven for the clueless, con artists, and wannabees). Stay away from megabuck color software until you can learn to use the basics in Avisynth and Virtualdub (which happen to be pretty decent for most of us). Get a long-standing industry standard on the subject: https://www.amazon.com/Color-Correct...s=books&sr=1-2. There are no workarounds. |
A bit harsh sanlyn, even if mostly accurate. :unsure:
Premiere has long been my preference for color grading, but I do want to learn DaVinci (free version) at some point. For easy cheat methods, I rely on VirtualDub, and Avisynth. Each is more powerful that I take advantage of, hence the cheat comment, but for power I again use Premiere. I really don't color grade that much anymore, my main focus is getting footage to the point where that can happen. Capturing and restoration. There are some good tutorials for color correction on Youtube, but equally as many bad (some clueless). Remember that any schmuck that make a Youtube video, so credentials matter. |
Sanlyn, go back and read my first post. You've made a lot of assumptions not based on what I actually wrote.
I'm asking how valid they are and if and how to add them to the workflow. I'm not looking for nor asked about any kind of workaround or some kind of magic button to press. And for the record, I already have that book and am slowly working my way thru it. Not everyone has your years of experience. Erich |
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Funny thing about experience ... you get rusty, forget stuff, refreshers never hurt. :o At any rate, to get back on-topic, without seeing the full video, I'm just not inclined to believe it's perfect as dubbed. George Lucas is famous (and infamous) for constantly going back and re-coloring Star Wars. Sometimes for the better, sometimes for the worse. But my point is that correction can be improved. So a test pattern on an old VHS should never be considered the epitome of accuracy. I've taken a look at the pattern. I do see tape noise, but it could be merely being critical of an old tape. Sometime, even with TBC, good cables, NR, it still has some degree of noise. That's determined by testing, just finding the best possible settings combo. You're probably fine, just double-check everything to be sure. |
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I've had a few tapes where the color looked pretty decent throughout (of those with color bars, the bars didn't seem to have anything to do with it), but that's rare and they still needed some correction to satisfy us OCD'ers. I've seen a few threads in other forums where people attempted to use the color bars to determine color grading values for various scenes in various tapes. The "corrected" samples they posted had terrible color correction. In most cases the poor guys obviously didn't know what they were doing, and much of the time they were apparently using uncalibrated monitors. You would also have results such as corrected (unquote) skin tones that looked like terminal liver disorders, and frames with bluish brights and greenish blacks that were transformed into clipped brights, reddish brights, and purple blacks. The next scene would have entirely different problems. Also, those color bars were set up for CRT displays, not for YUV capture. Years ago I tried using the colorbars to set capture levels but ended up readjusting levels within a few seconds or minutes of playback. Except for a very few old tapes that had obvious and consistent YUV tint problems from start to finish, I gave up long ago on trying to correct VHS color during capture. it's an exercise in clinical masochism. I do have a PA-100 proc amp that I use for checking and setting signal levels (which I still re-check with VirtualDub's capture histogram). Color problems with VHS aren't linear and are seldom consitent from minute to minute; I've found retail movie transfers to be among the worst. Often you'll need curves filters to make corrections -- those color wheels aren't precise enough. Quote:
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Thanks both of you, that's exactly the kind of first hand experience that makes this site so valuable.
As for re-colored films, I just watched the Blu-ray release of Disney's 20,000 Leagues Under the Sea - a favorite film of mine. Yuck! The "restoration" consisted of removing the film grain and changing the color balance so badly I'll happily go back to watching the lower resolution original transfer DVD version in the future. Erich |
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