VHS-C has crushed brights, but regular VHS does not?

[mirkorm]

Hi everybody, thanks again for all the information on this website, you really helped me a lot with VHS capture and I've been able to organize a workflow that meets my needs.

I now noticed something odd: I have this one recording both on the original VHS-C from the camcorder, and on a regular type VHS that was done back in 97 connecting the camcorder to our old VHS deck.
Now the odd thing is that the one on the original VHS-C has crushed brights, with small to no detail on them, and the one on the VHS doesn't have that spike in brightness and kept the details.

Now: since the VHS was taken from the original it means that the original one has those details somewhere for the copy to show them so: is there a way to grab those details back from the VHS-C? Do VHS-C and regular VHS need different ways for digital capture? The strange thing is that the reg. VHS was digitally captured with the same hardware as the original so it shouldn't be digital-capture hardware related.

In the attachments I loaded the same frame from both captures:

-On the unprocessed one we have the unprocessed video from the regular VHS on the left, and the unprocessed one from the VHS-C on the right.

-On the color corrected one we still have the unprocessed one from VHS on the left, and I tried to color correct the VHS-C capture on the right but I still don't have much detail showing.

As a reference for the loss of detail on the brights on this frame I took the wrinkles on the back of the yellow pajamas.

On this particular case the details missing are not that life changing and I have the VHS with a better quality anyway, but it's the only one of which I have both and I noticed that all VHS-C have crushed brights.

Thanks

[bookemdano]

What playback device(s) are you using for these tapes? Are you putting the VHS-C in a VHS adapter and playing it in the exact same deck as the VHS copy? What brand/model of VCR/camcorder are you using?

[mirkorm]

Hi bookemdano thanks for your answer.

Yes, I use the exact same vcr and the same virtualdub settings without changing anything, the only difference between the captures is that I use the VHS adapter for the VHS-C as you mentioned.

As for the VCR I have a Sony SLV-SE-45, definitely not top choice but I used it for both of the captures without changing anything.

[latreche34]

I would capture the original VHS-C tape and change levels in vdub using histograms as guidance.

[mirkorm]

Alright, thanks latreche34 I'm going to try the VHS-C capture with different levels and report back.

Capturing in lossless format (huffyuv) I thought I had very much information and a virtually infinite postprocessing margin like raw/s-log formats for digital video recording, but I guess it's different for analog to digital capture.

[mirkorm]

Yes, thank you very much, the image is still not as good as the VHS one but close enough so I guess I'll have to play a little with the levels.

With brightness, contrast, hue and saturation I'm already familiar with though but I'm a bit confused as to the gamma level: usually they range from 1.0, 1/1.8, 1/2.6 but on the capture card proc amp on vdub they go from 0 to 50, does it use a somewhat different scale? I'd like to study the situation better but I'm going a little blind changing the gamma parameter.

[timtape]

We only have to clip one link in the chain and its clipped on everything downstream. All the downstream headroom in the world won't fix it. Be careful tweaking proc amp gain! Remember that capturing is not 'enhancement' or 'restoration'. The aim is to make a perfect copy of the data on the tape. Its an objective exercise, not a matter of opinion or interpretation.

[mirkorm]

Yes, I'm gradually tweaking it while watching the preview, but the proc amp uses parameters all its own: even with hue, I thought it changed the overall image color, sort of like a filter to compensate for a skewed white balance but it's not that, it changes so slightly I can't seem notice what I'm actually changing... I really hope there is a proc amp levels guide or I'll go crazy trying to tweak them.

[bookemdano]

That's really interesting that the original would have blown highlights but not a second-gen copy.

Do you happen to have (or at least have access to) another VCR on which you can test both tapes? I really wonder if this comes down to a quirk of that particular Sony. Since (as you said) that detail must be present on the original tape for it to be present on the copy (which it definitely is). So that would seem to point to an issue with the deck. By chance, was the copy originally recorded on this deck?

[timtape]

Quote:

Originally Posted by mirkorm

Yes, I'm gradually tweaking it while watching the preview, but the proc amp uses parameters all its own: even with hue, I thought it changed the overall image color, sort of like a filter to compensate for a skewed white balance but it's not that, it changes so slightly I can't seem notice what I'm actually changing... I really hope there is a proc amp levels guide or I'll go crazy trying to tweak them.

Have you tried using the default settings, meaning flat, neutral? Often its the best way. Proc amps were useful in the past when "mastering" to another analog tape generation but for capture to a strong digital format they can be redundant and in inexpert hands do more harm than good. Capturing the poor dynamic range of VHS should be easy, especially home camcorder footage.

[hodgey]

Quote:

Originally Posted by bookemdano

I really wonder if this comes down to a quirk of that particular Sony.

I have used some closely related sonys quite a bit. There isn't anything in them that should be blowing out levels on playback on it's own, though the "OPC" function will adjust the sharpness and possibly noise reduction a bit depending on the tape condition so it's possible that could affect the levels a little on the end result. This one doesn't have EDIT mode like some similar Sonys do, tho OPC can be turned off if it doesn't perform well.

Anyhow, I suspect the dubbing process is more likely to have affected the video levels. Maybe the output from the original tape ended up a bit high and the AGC in the dubbing deck adjusted to avoid clipping.

There is some details about how to adjust levels with virtualdub here. Basically you want to enable the histogram in virtualdub, and adjust brightness/contrast so that you don't see anything being crushed at the each side, ideally nothing being in the red on the right. (Not noted there is that some capture cards will clip at y=16 and/or y=235, you will be able to see that in the histogram preview as the data won't go fully out to the edges.)

[mirkorm]

Quote:

Originally Posted by bookemdano

That's really interesting that the original would have blown highlights but not a second-gen copy.

Do you happen to have (or at least have access to) another VCR on which you can test both tapes? I really wonder if this comes down to a quirk of that particular Sony. Since (as you said) that detail must be present on the original tape for it to be present on the copy (which it definitely is). So that would seem to point to an issue with the deck. By chance, was the copy originally recorded on this deck?

Unfortunately I don't have another VCR as it's already been very hard finding the one I ultimately got...

My guess is that maybe either the old VCR, with which the VHS-C was copied to VHS back in the day, the camcorder (both VCR and camcorder were Philips but I can't remember the exact models) or the S-Video connection that was used, already performed some kind of enhancing or filtering for the copy... but not having another VCR I can't tell for sure.

Now I'll try to struggle with the capture levels but I still can't figure out what gamma and hue of the proc amp actually do to the image and to what degree according to their min to max values.

PS: Now that I think about it I have a VHS transfer of a VHS-C my cousin gave back in the day, because he brought along his own camcorder that day, and the levels are completely different, so I guess there was some kind of filtering going on in the camcorder to VCR transfer.

[mirkorm]

Quote:

Originally Posted by timtape

Have you tried using the default settings, meaning flat, neutral? Often its the best way. Proc amps were useful in the past when "mastering" to another analog tape generation but for capture to a strong digital format they can be redundant and in inexpert hands do more harm than good. Capturing the poor dynamic range of VHS should be easy, especially home camcorder footage.

Yes, the frames I posted were both captured with the proc amp default levels.

[mirkorm]

Quote:

Originally Posted by hodgey

I have used some closely related sonys quite a bit. There isn't anything in them that should be blowing out levels on playback on it's own, though the "OPC" function will adjust the sharpness and possibly noise reduction a bit depending on the tape condition so it's possible that could affect the levels a little on the end result. This one doesn't have EDIT mode like some similar Sonys do, tho OPC can be turned off if it doesn't perform well.

Anyhow, I suspect the dubbing process is more likely to have affected the video levels. Maybe the output from the original tape ended up a bit high and the AGC in the dubbing deck adjusted to avoid clipping.

There is some details about how to adjust levels with virtualdub here. Basically you want to enable the histogram in virtualdub, and adjust brightness/contrast so that you don't see anything being crushed at the each side, ideally nothing being in the red on the right. (Not noted there is that some capture cards will clip at y=16 and/or y=235, you will be able to see that in the histogram preview as the data won't go fully out to the edges.)

Thanks hodgey, I'll try to tweak the settings as explained on the guide and leave the hue and gamma levels as they are until I figure out what they do.