Transparent bands across negative

Discussion in 'Film and Processing' started by n9119, May 26, 2020.

  1. Hi. I've been searching a lot about this problem I'm having and couldn't find a proper answer, so I thought it would be best to post it here.
    I developed a T-Max 400 pushed to 1600 and these transparent streaks appeared. They look black when scanned.
    This isn't the first time this happens to me. I changed my camera because at first I thought it could be some kind of leak, but then the same streaks appeared.
    I prepared a new developer, stop bath and fixer and nothing changed. (I'm using 'Romek', a brand from Argentina)
    Am I doing something wrong when processing? Maybe agitating? I've been developing my own film for three years now, never had a problem like this, but it happened in almost every one of my last rolls and I can't seem to get pass through it.

    Another fact is that these are films that traveled from Europe to South America... could this have something to do with that?
    ALSO, most of these pictures were taken directly from my TV screen. Could the lightning from it be altering the picture?
    I keep thinking and trying to figure out what this is about, but I'm running out of answers, it's honestly so annoying, every time I develop and take the film off of the tank I get so frustrated.

    I hope you can help me. Thanks in advanced

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    Last edited by a moderator: May 27, 2020
  2. It could be due to airline baggage scanning.
     
    oleksandrk likes this.
  3. The image on a TV screen is scanned in scan lines, from top to bottom,
    usually in about 1/30 of a second.

    This was well known in the CRT television days, and isn't quite the same in the
    now common LCD sets. I suspect that it is in plasma sets, though there aren't so
    popular right now.

    You want a shutter speed not faster than 1/30, probably 1/15. You might still get
    some effect, but it should be much less.

    This used to be a good way to calibrate shutters. Take the picture, especially
    with a shutter speed faster than 1/60, and count the scan lines. With a focal
    plane shutter, you get a diagonal stripe, and count vertically though a stripe.

    The scan rate for US sets is 15734kHz, slightly different in other countries.

    Light leaks and others will give black marks on the negatives, white on positives.
     
  4. X-ray scanner damage would fog the film and result in blackened areas on the negatives, as would light fogging. Both would result in white or light patches in the final positive image.

    Also, the streaks appear to be wavy, run across frames and join up, unlike the straight lined bands you'd get from TV scan lines, but scan line banding can't be ruled out.

    It looks as if either the film stuck together in the developing tank, or insufficient developer was used.

    You don't get any of this needless strife with digital BTW.
     
    Last edited: May 28, 2020
    ajkocu likes this.
  5. The first post says transparent on negatives, black on scans.

    I have a hard time figuring out the images, but I suppose they don't look like
    I would expect from TV scan lines. Actually, I don't see scan lines at all.
     
  6. James G. Dainis

    James G. Dainis Moderator

    In one image showing the person's hands, the hands go horizontally; in another image of the same frame the hands go vertically. It is hard to get an idea of whether the bands are flowing horizontally or vertically if the OP does that. He can see the negative and knows which way the bands flow but we can't.
     
  7. If it were baggage CT scanning I would expect to see damage outside the image frame as well as within. I don't see that in the filmstrips shown -- but I agree with comments above that it is not entirely clear what we are looking at. I would also expect such damage to be dark on the negative. I think the reference to a TV screen is using it as a light table to photograph the negatives, but the damage isn't consistent across the strip. Though just to be safe, I would go for a long enough shutter speed to include multiple scan frames.

    If the bands were dark, one might suspect focal plane shutter leaks but what (I think) we are seeing is more like an obstruction in the light path -- something loose flopping around in the camera? Mirror bumper? Note so far we don't anything about the camera other than it's 35mm!
     
  8. What camera did you use? Could be a free floating piece of dense hair between film and back of lens.
     
  9. Start again. Expose fresh film at box speed, use Kodak or Ilford developer and agitate 5sec for every 30secs

    If that problem is persisting with different cameras, then the problem is in the way the film is being exposed and/or processed.

    How much did you "push" the development, and what sort of reputation does Romek chemicals from Argentine have, good or bad ?
     
  10. The OP says it's happened with different cameras.
     
  11. My appology fot not readig the entire OP post.
    This is from google search:
    VSYNC.png
     
  12. Hmmm -- what Pavel says about vertical sync is true -- however if the TV is adjusted correctly, the VSync bar should not be visible on-screen. Anyway, re-reading with more coffee consumed, OP does say the photos are taken off a screen. That would certainly help explain why the bars in question could run along the length of a frame and end nicely at the frame edges. Perhaps what we are seeing is not the vertical sync, but simply not enough scan lines for a full frame refresh; this puts us back to needing a shutter speed long enough to cover perhaps two or three frames at the frame rate. As suggested above, I'm not at all sure what sorts of tricks go on in the latest LCD displays. Given the wide range of input some displays take, there may be a two-step process for conversion and display. Given this and the note it occurred with more than one camera, the problem would definitely appear to be in the actual taking of the photo, not subsequent handling or processing. I very seldom photograph off a display screen, but can't say I've ever seen such an effect this obvious.
     
  13. Here's a late color LCD display taken with flash on my Mamiya Metra 35mm when I was taking a photo of my lounge room while testing the camera just after repairing it. The film was Ilford FP4 exposed at box speed. I've expanded the image and took a screen shot of just the TV set. Make of it what you will. Perhaps the flash stopped the electronic oscillations.

    Black TV lines.png
     
  14. Most older film cameras require a flash synch 'X' speed of 1/60th or slower. This is slow enough to capture an entire TV frame at the US rate of 60fps.

    The old analogue TV used an interlaced scan. Meaning that half of the scan lines were transmitted at the same rate as the local mains frequency - 60Hz in the US, and 50Hz in the UK, for example. Therefore it took 1/30th of a second to transmit/scan all of the frame lines in the US, and 1/25th of a second in the UK (I.e. 30 or 25fps).

    However, because of this interlacing of two half-resolution images, you only get strong banding if you exceed the half-frame scan speed - 1/60th or 1/50th, and usually only with a focal-plane shutter.

    Nowadays, LCD technology stores both half-frames in memory and displays them simultaneously; refreshing the screen at the full frame rate of 50 or 60Hz. Some displays even double up on those refresh rates to reduce visual flicker that some people are sensitive to.

    Therefore it's probably 'safe' to use a shutter speed of 1/60th or slower with an LCD display. But certainly not 1/125th or higher.

    The OP tells us that he rated the film at 1600 ISO (why?), and a TV or monitor at any normal brightness is going to need a high shutter speed <1/60th with an aperture of around f/5.6 at that ridiculous ISO speed. So it's a fair bet that the OP was using a too fast shutter speed for the job of photographing a TV screen.
     

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