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  1. Hi All

    I captured an old black and white film using virtual dub, and i would like to correct the picture as its quite dark, i have been messing about with the brightness/contrast in Virtual Dub but cant seem to get a good balance, im sure there are other factors which should be considered, can anyone give me some advice on where to start please? Attached is a short clip without any prior adjustments.

    Many Thanks

    DMS
    Image Attached Files
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  2. You need to capture again with proper proc amp settings. You have crushed all the dark and bright areas and there is no getting back the details that have been crushed.
    Last edited by jagabo; 11th Apr 2021 at 06:49.
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  3. Originally Posted by jagabo View Post
    You need to capture again with proper proc amp settings. You have crushed all the dark and bright areas and there is no getting back the details that have been crushed.
    Hi Jagabo, thanks for the quick reply, i thought that may be the case, is there a flat level i need to be adjusting to? as the film is bright in some scenes and dark in others!

    cheers

    DMS
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  4. Video cameras have a different way they capture dark to light than does movie film. Movie film is designed to be projected through a VERY bright light onto a screen in a big room. As a result, the dark sections of movie film have to be much darker than their video counterpart so that the image doesn't look washed out on the screen. Thus, when you capture film, the shadows are always going to look too dark, unless you use a special camera which has an adjustable "gamma curve" which makes the camera more sensitive to the really dark sections of the film and makes those portions brighter, the same as what happens when projected with a white hot projector bulb.

    When using a normal video camera to capture the result, the trick is to expose for the highlights, while letting the shadows stay too dark. I turn on the zebra patterns on my video camera and adjust the exposure until the zebras almost disappear. Since the overall exposure on the film can change from scene to scene, you want to keep the camera's auto exposure enabled, so the usual trick is to either use the Spotlight function, if your camera has it (most Sony cameras do) or simply use the AE adjustment to subtract a little from the auto-exposure.

    Then, in post, using your NLE, you apply a histogram brightening function which brightens the shadows, while leaving the exposure of the midtones and highlights untouched.

    You NEVER want to let the highlights get over exposed because once you exceed 235 or 255 (depending the luma model used) you have reached pure white, and all detail will be lost forever.
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  5. You can Up the gamma by about 20 units in virtualdub with colormill, that should do it
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  6. Colormill is a great plugin for color, and its gamma adjustment may work, but to do the job right, you would be better off using something which lets you decide how much gain to apply to each section of the histogram. For film, you don't want to touch the darkest pixels, because otherwise the result will look washed out. However, starting with levels of 2 & 3 (out of 255) you want to start gaining quite a bit, all the way through the 30s and 40s. After that you want to taper that gain pretty quickly. There is no science: you have to do this "by eye" on a well-calibrated monitor.
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  7. Obviously, you can make some improvements by adjusting gamma with Colormill or Levels, or by using a knee curve in Gradation Curves. But I would try getting a better cap to start with. Bring the black level up and the white level down using the capture device's proc amp. Hopefully that will reduce the crushing of darks and brights.
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  8. Thank you for your replies, I will give colourmill a try. Just for clarity, the capture was taken from a VHS tape. I think the original film transfer to VHS was poor to start with, I think trying to correct the brightness at the capture stage will be difficult as there are a lot of dark and light scenes in the movie and trying to get level balance is really difficult.

    Thanks again for replying to my question.

    Cheers

    DMS
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  9. Member
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    Originally Posted by DMS View Post
    Thank you for your replies, I will give colourmill a try. Just for clarity, the capture was taken from a VHS tape. I think the original film transfer to VHS was poor to start with, I think trying to correct the brightness at the capture stage will be difficult as there are a lot of dark and light scenes in the movie and trying to get level balance is really difficult.

    Thanks again for replying to my question.

    Cheers

    DMS
    Much better for the dark scenes to be a little too bright, that can be corrected post capture.
    But if they're too dark, shadows are crushed and non-recoverable.
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  10. Originally Posted by jagabo View Post
    You need to capture again with proper proc amp settings. You have crushed all the dark and bright areas and there is no getting back the details that have been crushed.
    Originally Posted by jagabo View Post
    But I would try getting a better cap to start with. Bring the black level up and the white level down using the capture device's proc amp.
    What do you mean by this? I thought we must capture raw AVI at 4:2:2 then do all the adjustments in software afterwards. Are you saying its sometimes better to capture with specific settings and not try and do them in post?
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  11. Once the captured signal is clipped you can no longer recover the clipped part with post processing. What is lost is lost.
    You should therefore adjust the proc amp to keep the luma Y preferably in the 16 ..... 235 range for capturing, which provides some headroom for the luma. You can use avisynth's histogram("classic") for checking.
    In your video sample.avi you have clipped (clamped, crushed) blacks at Y=16 and some clipped whites at Y=255.

    Image
    [Attachment 58538 - Click to enlarge]
    Last edited by Sharc; 22nd Apr 2021 at 05:54.
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  12. So you have to do a clipping analysis before doing a full capture, and adjust so end capture is 16-235.
    What is the easiest way to view clipping in a GUI?
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  13. Originally Posted by agisthos View Post
    So you have to do a clipping analysis before doing a full capture, and adjust so end capture is 16-235.
    Yes, a levels analysis is highly recommended.
    What is the easiest way to view clipping in a GUI?
    For example, load this script in AvsPmod
    Code:
    AVISource("Sample.avi")
    turnright().histogram("classic").turnleft()
    Edit:
    I don't know what proc amp adjustments your capture infrastructure supports. The discussion here might be helpful:
    https://forum.videohelp.com/threads/401349-GV-USB2-Capture-Stick-What-s-In-It#post2615895

    Or if you can't adjust the proc amp for capturing you may try as postprocessing filter something like
    Code:
    Levels(0,1.25,255,0,235,coring=false)
    Last edited by Sharc; 22nd Apr 2021 at 07:52.
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  14. Originally Posted by agisthos View Post
    So you have to do a clipping analysis before doing a full capture...
    You make a few short sample caps from different parts of the film (I do 30 seconds or so at a time), study them, adjust the proc amp, and then capture the complete film.
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    I'm a rank amateur at this, so please correct me if I'm wrong, but can we use the histogram in Virtual Dub to achieve the correct setting for capture, like this?

    - Put VDub into capture mode, choose Video>Preview, display the Histogram (Video>Histogram)

    - Play video and watch the histogram, adjusting Brightness and Contrast to set the levels within the safe areas - up to the red marks (I use Jagabo's Graphstudio method for Proc Amp control).

    A video could be checked by cueing to various points and rechecking histogram and adjusting the levels before doing the capture. If there's obvious differences then very bright and very dark sections could be captured separately.
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  16. You can use VirtualDub's built in histogram but it's a bit tricky -- you lose all spacial information so it can be hard to tell what parts of the picture are out of bounds. For example, the out of bounds area may be the black bars at the left and right of the frame. You don't really care about those bars. I suggest you crop 32 pixels off all four edges to eliminate the edges from the histogram.

    Your earlier sample shows blacks crushed at Y=16. That may be what's on the tape. But it may be that your capture device crushes blacks there. Bringing the black level up while capturing may or may not reveal detail in the dark areas. The white level is too high and crushed at 255. Bringing it down will probably reveal more details in bright areas.
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  17. Thanks for the replies to this, unfortunately Iíve had pc issues and had to reset my pic, my dazzle capture device no longer keeps the audio in sync, or maybe itís the windows audio driver that doesnít work, anyway Iím going to have to work out which way to go next, old windows 7 pc, or try and find a capture device that actually works with w10.
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  18. Hi All

    Me again, finally got my capture device working again, but this time it will only work using AmarecTV, tried everything with Virtualdub and it just doesnt like the audio driver! anway, i have done another test capture and tried adjusting the Proc Amp settings, from what i can tell there isnt a histogram on amarecTV so im having to eyeball it, not ideal as im no expert! Anyway here is a clip attached, is this capture any better?

    Thank you

    DMS
    Image Attached Files
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  19. The black level is way off (the brightest whites are blown out a bit too):
    Image
    [Attachment 58749 - Click to enlarge]


    If you pull it down to full black it gets too dark (ColorYUV(off_y=-42)):
    Image
    [Attachment 58750 - Click to enlarge]


    The original film probably had darker shades that were lost in the telecine. So you might use a compromise setting (ColorYUV(off_y=-25)):
    Image
    [Attachment 58751 - Click to enlarge]


    Pick whatever compromise setting you think looks best.
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  20. Hi,

    Im back again, finally got Virtual Dub2 working again for capturing! Anyway, im wondering if you could check the attached file to see if i have improved on my capturing? Many thanks in advance.

    DMS
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  21. That looks a lot better. Slightly darker black and brighter whites might be a little better.
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  22. I also did it: https://www.sendgb.com/upload/?utm_source=lmZ8pv3M19e

    Neat video is unbeatable!
    Last edited by Truthler; 21st Sep 2021 at 16:09.
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  23. Member DB83's Avatar
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    I'll ask a few questions here rather than 'elsewhere'


    Somewhat confused since there are two different clips both named 'test2' neither of which is the 'unbeatable' clip as above.


    Now I recc Will Hay but not being an expert on his work may I ask:


    1. The title of the film
    2. Is this sourced from official PAL vhs or some other means


    The visual issue I have is the artefacts that are prominent around faces which looks like bad interlacing but can not be turned off at playback.
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  24. Hi DB83

    Thanks for replying, the clip im interested in is the one from post 20, this is the most recent one, i have been trying to improve the Brightness/Contrast during capture using the Virtualdub histogram. Im after a bit of feedback about the quality of this capture. This is how i captured it:

    The film is 'Ask A Policeman' (1939) it is from a PAL official VHS release from Carlton International, my copy is an original copy, i captured via a Toshiba VCR with a Scart out to a Panasonic DMR-EH50 (all filters turned off) then S-Video out to a Dazzle Capture. I captured using Virtualdub2 and Lagarith.

    Ive noticed that the capture looks blocky when in full screen, not sure if this is normal.

    Cheers

    DMS
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  25. Member DB83's Avatar
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    Not really sure if this is a clever workflow. The Tosh will be composite out? and the Panny may well be borking the picture hence all that disturbance. S-Video from there will not really IMO do what it is meant to do.


    Now I see two vhs versions of this film on Ebay. They are probably from the same source just different packaging.


    The other possibility is that the pattern that actually appears throughout the picture - blocky is not the right term - is cable interference. So, yes, NOT normal.


    Normally, if a tape is rare and not on dvd I would also pursue a vhs capture but I see all the films on dvd and there is a set on Ebay (used) for £8.


    But I am prepared to make you an offer.


    Allow me to do a transfer from that tape with my modest set up. No charge to you. I will, hopefully, gain a free copy of the film.


    No improvement = no loss (and if I damage the original I will replace it.)


    PM if interested.
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  26. Hi DB83

    Thanks for the advice, i tried capturing directly from the VCR but the capture was not as good as it is via the passthrough. I might try some different leads (I have loads of them). Iím not really after someone else doing a capture for me, this is more of a hobby just to give me something to do, so I would rather try and get the best possible capture myself, Iíve been trying to source a SVHS player locally but they donít seem to be many about where I am (Lincolnshire). I just wanted someone elseís advice on the capture to help work out how to improve on it. If I do manage to get a good capture I will share the file with you.

    Thanks

    DMS
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  27. There's something odd with the cap in post #20. It looks like it was captured at a lower resolution then upscaled with a PointResize. That is causing lots of aliasing and accentuating noise.
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  28. Member DB83's Avatar
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    That's ok. We all want to achieve the best we can.


    I am also suspicious of the Dazzle given that Win10 'broke' it.


    The offer will stand regardless. I might even get some of these tapes crazy as it may sound. There is a certain 'innocence' about pre WW2 film.
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  29. Member DB83's Avatar
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    FYI The film (probably a dvd source) is available on youtube.


    https://www.youtube.com/watch?v=ah0gR6HlG8k


    Picture wise it is quite dark and there are constant minor light changes probably caused at telecine. Other than that it is quite clean with no obvious noise.
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  30. Originally Posted by jagabo View Post
    There's something odd with the cap in post #20. It looks like it was captured at a lower resolution then upscaled with a PointResize. That is causing lots of aliasing and accentuating noise.
    Hi Jagabo

    I have checked all my settings and I definitely captured at 720x576 and saved using lagarith. Maybe the dazzle is pretending to be capturing at 720x576!

    DMS
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