I can't get my histogram into the red with my proc amp. Is my capture card clipping those color values internally?
I am kind of wanting some advice for using my proc amp. I am thinking I should not mess with it on tapes where my histogram looks like this but idk if that's the right idea. From what I hearing the tint changes the relationship of the colors that are wrapped around the luminance in the YUV colorspace and you use bright and contrast to control the levels on the histogram.
I am also just wondering how everything looks to you guys before I get started.
I just have to get different cables before I start. I think I am going to order some Blue Jean Cables.
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I asked that question too early without looking through the forum enough on that subject. So most cards clip out of bounds colors. I’ll look through the forum some more and redo the tape tomorrow. I’m just kinda messing with all that now until I get my cables.
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I adjusted (histogram 2.jpg, test 22.avi) the brightness and contrast on my proc amp in my TBC 3000 to properly expose the video. Now I just need to calibrate my IPS monitor so I am not adjusting it to an uncalibrated monitor.
Just remember that your eyes take precedent over any meter/graph/-gram. If it looks too bright, it is, regardless of what a meter says. But again, monitors must be calibrated for that sort of override.
Exposure (luma) levels can vary a lot from tape to tape or scene to scene, so I think as long as playback of your captured file is without flat-lined clipping (flat peaks of waves on a software waveform monitor above 100IRE), you should be fine to edit it back into legal ranges later without data loss.
I will say I've adjusted a freshly recorded color bar tape to be at the correct levels using a vectorscope and waveform monitor, but then after putting in a different commercial VHS tapes, levels were way higher and resulted in clipping with those same settings. So you almost have to check levels with each tape you're doing at the brightest scenes to make sure luma isn't clipping for that specific tape. Using something like a hardware waveform monitor can make that easier to monitor live, or you can use a software one if your recording app allows the waveform monitor to be visible during live recordings.
Seems relatively rare that chroma will clip since those levels are usually far below legal limits for most content types.
you should be fine to edit it back into legal ranges later without data loss.
The color data outside of the legal limits isn’t captured by my card so I can’t edit it back. It would just be lost detail in my highlights and shadows unless I use my proc amp to bring my color values into the legal limits before the signal is captured by my capture card. You can see it on the histogram when you adjust with a proc amp how it brings the colors into the legal limits so they can be captured.
The color data outside of the legal limits isn’t captured by my card so I can’t edit it back. It would just be lost detail in my highlights and shadows unless I use my proc amp to bring my color values into the legal limits before the signal is captured by my capture card.
100% correct.
You can see it on the histogram when you adjust with a proc amp how it brings the colors into the legal limits so they can be captured.
The color data outside of the legal limits isn’t captured by my card so I can’t edit it back. It would just be lost detail in my highlights and shadows unless I use my proc amp to bring my color values into the legal limits before the signal is captured by my capture card. You can see it on the histogram when you adjust with a proc amp how it brings the colors into the legal limits so they can be captured.
Are you using the software proc amp settings for the capture card (in software) or something else to adjust your levels? If the levels are that high, the VCR or your TBC may need some adjusting?
Are you using the software proc amp settings for the capture card (in software) or something else to adjust your levels? If the levels are that high, the VCR or your TBC may need some adjusting?
I am using the proc amp in my TBC 3000. It’s a hardware proc amp. A lot of TBCs have built in proc amps. A lot of analog tapes have illegal color values. That is why manufacturers built proc amps into TBCs. There are standalone proc amps too which are really strong but I believe they reduce your signal quite a bit and are a use only if you really have to. It is ideal to edit in both the analog and digital domains. Some errors are baked in if they aren’t fixed in the analog domain before capture. On the first histogram you can see that the sides are cut off on the far left and the far right. That is clipping of my highlights and shadows. All values below 16 will be 16 and above 235 will be clipped to 235.
I don’t think my VCR or TBC are the reason that my values are illegal but I don’t know for sure. With the way I bought my TBC uncertainty on stuff like that kinda comes with the territory. I can’t calibrate my TBC. That is a factore if you are wanting to evaluate a TBCs performance over another though. Tgrant calibrated my VCR. Hopefully it’s good. It’s been a while since he calibrated it. My monitor isn’t calibrated either yet. It was factory calibrated but that’s also been a while and factory calibration doesn’t get as wide of a color gambit as calibrating yourself with a Spyder. I don’t think my histogram levels are really high or really low. The more seasoned members here have seen color values way higher and lower than mine. It’s the format and the fact that people didn’t worry about having things actually properly exposed before shooting with their VHS camera. They don’t dim the lighting or anything like that. They just pulled out the camera and shot.
Legal signal levels mean legal for broadcast. E.g., luma levels above 100 IRE can cause interference in the audio within the broadcast signal. As noted in other posts some gear will force legal levels, potentially by clipping out of range values.
For analog video signals, maintaining proper signal levels requires impedance match through out the signal chain; 75 ohm outputs feed 75 ohm inputs. IA100 IRS signal will appear to be 114 IRE if the it feeds a 100 ohm load, or 80 IRE if a 50 ohm load, Cable impedance is important for all but short (compared to wavelength) cable runs (to avoid ghosts). Also equalization may be needed for longer runs to offset cable losses, especially at higher frequencies.
The reason for color bars and tone are to set levels through out the system. Consumer gear and aging gear may or may not provide proper pass-thru levels to the next stage. Bars are also used to setup monitors to display proper black and white levels.
While (for NTSC) 7.5 IRE is black and 100 IRE is white it is not unusual to see camcorder digital recordings with highlights above 100 IRE and shadow details below 7.5 IRE. Outputs from analog VCR's will depend on both the original recording levels and how the VCR is calibrated.
I definitely am using bad cables. I can see quite a bit of ghosting. I’ll fix that before I start capturing.
Quote:
The reason for color bars and tone are to set levels through out the system. Consumer gear and aging gear may or may not provide proper pass-thru levels to the next stage. Bars are also used to setup monitors to display proper black and white levels.
Exposure (luma) levels can vary a lot from tape to tape or scene to scene
it’s really color balance that changes from scene to scene minute to minute. That’s why people usually stay away from hue on their proc amp. You can play an analog tape back twice and it will measure differently on your scopes each time. Digital is the same each time. Luma changes too but you can set it for a worst case scenario and do it in segments. Adjusting hue in real time is just a bad idea. Jwillis covers that all really well in that last link.
We're really going to get in the weeds on this one.
You're probably seen me post that "no TBC is perfect" and that "all TBCs add some % of processing noise".
That dual statement can be read two ways
1. The wrong way. Morons will say "if none are perfect, and all add noise, then all are fine!" which ridiculous and utterly stupid. It's the political equivalent of "they're all the same?" (NO!) spouted by low-knowledge/no-knowledge voters (or even non-voters). That's what you say when you don't know know what the hell you're talking about.
2. The proper way, the complicated way.
TBCs don't really have "shades of gray" but more like "shades of white" or "shadese of black". It is fairly binary, good or bad, black or white. But you can have charcoal and eggshell in their.
DataVideo TBCs have more of an "analog look" to them (or "analog processing" or "analog feel"). Certain DataVideo models, and certain generations of those models, are indeed some of the best TBCs ever made. (For example, DataVideo TBC-3000 4th gen, and potentially your interesting 5th gen. Note that I once believed 4th was 3rd, but a quirky quasi 2~3 was discovered, making it 3rd now, bumping former 3rd to 4th. And of course those are only good when working properly, and many sadly now are not.)
And yet, not perfect.
Best is not perfect.
All TBCs "lock" onto signals, but not how most people understand. Some are more like anti-lock brakes, while others are bicycle brakes. DataVideo proc amps locking is not really internally matched against a test patterns as the Cypress are, and can therefore waiver a bit from session to session. It's not large, but present. Member nicholasserra has discussed this before at times, something he observed with his own unit, and for that reason calibrates against a patterns per session.
Cypress is not really like this, though it has more of a "digital look", or "pixel look" to it. However, that doesn't mean it's noisy as most laymen would think (ie, they think it badly made DVDs, old Youtube videos, VCDs, etc, as having digital/pixel look; that's not what I refer to). Analog and digital processing have distinct looks, even when both are completely devoid of noise.
Sometimes jwillis84's older posts can be off (as he was/is still a relative newbie to video; though a smart one, given his jobs/resume), but that exact post was quite accurate that I just saw from quick reading it.
You can get overly anal about image values, but the goal should be pragmatism. Get as close as possible, but without being lazy, without being OCD. At some point, you do need to remember it's consumer analog, VHS, NTSC, etc, and was never perfect, will never be perfect. Even "perfect digital 1's and 0's" is nonsense, and not perfect.
You don't want grandma to be sunburned at Christmas, because the colors are fubar. But if grandma is sunburned by the pool in summer, you don't need to argue whether the hue should be 1% towards orange or 1% towards red. Have some sense about it all.
