Hasselblad + off camera flash backlighting = odd linear flares...?

Discussion in 'Medium Format' started by daniel_muchnik, Nov 9, 2010.

  1. So I've noticed this with a lot of hassy photos. When a flash is too close to the edge of the frame it makes this trademark flare of sorts. I'm just wondering what exactly is causing this... where and how exactly is the light bouncing to do this? WIth other cameras and strong backlighting, you can sometimes see when the light overpowers the anti-halation later and bounces back, but the flare looks very different is is always closer to the edge. I'm just curious as to what exaclty is going on. Here's a link to an example from a roll I developed last night.
    [​IMG]
     
  2. This is not flare. If it were, it would affect the skater too. It looks like spill from the flash, or possible a reflection against the back wall. You might consider barn doors or a flag to control the light.
     
  3. I really dont think its spill just because of how perfectly vertical the cutoff is. Here's another example of the same thing with no wall for the flash to reflect off of... this one isnt mine.
    [​IMG]
     
  4. Dan, I don't recall seeing this with a Hasselblad before. Can you give us more info? You say the second pic isn't yours. Is it with the same camera? Your flickr stream shows similar images, but without the effect. Can you give us more to go by? Did you leave the dark slide in the side of the camera? Have you had the back serviced lately? Maybe a light leak? The key is whether the two photos were made using the same back or camera. If it was the same back, but different film, I would say your seals need replacing (something you can do yourself with a kit on fleabay or directly from Hasselblad).
     
  5. It is an internal reflection, yes. Not a lightleak, or any of the other suggested 'probable causes'.
    I do not know where and off what light bounces to create this exactly though.
    Here's one i prepared earlier:
    [​IMG]
    You can see that the source of light (the sun, yes) is just outside the frame.
    And that the reflection's location is closely related to the position of the source of light.
     
  6. Fascinating. I've probably exposed 15,000 images with Hasselblads, and haven't run into this.
     
  7. I get much the same thing with my Rollei 35 with back light, though the edge is at the top and fairly close to the edge so I can crop it out. I'm pretty sure the cause is internal reflections/flare that is stopped by a baffle near the edge before it can reach the film, giving a visible edge.
     
  8. I say embrace it, like the Holga folks would. :)
     
  9. Interensting!
    Could you share some info like: Which lens?, where you using a UV Filer? Where you using the square lens hood? Have you tried if the position of the reflection changes with or without the lens hood?
    I'll try to check if I can observe this by using a SWC focusing screen adapter mounted on a 500c/m, shutter on B (T)
     
  10. And where would the light source be in relation to the camera. I'd like to know how to avoid it, since I've never experienced it. That would ruin your day, particularly for a paid shoot. I never shoot without a lens hood, so I wonder if that helps.
     
  11. My example was 'created' using a CF 40 mm lens on a 500 C/M camera.
    No filter. No lens hood except the one that came on/with the lens.
    I think that the position of the light source plays a key part in this. Head on, just outside the frame
    Difficult task for a lens hood, i think.
     
  12. Strange indeed, don't quite recall such a specific side and effect. Where's Sherlock when needed....
     
  13. It is a reflection inside the camera body. I was able to observe it and I'll try to capture it over the weekend and hopefully post them here.
    When an extremely bright light hits the side panel in the camera body, there is a strong reflection. There is a frame in the back of the body, that starts out a couple of milimeters from the film plane, that shades a little bit of this reflection and that's why it does not starts from the edge.
    It occurrs only at a specific narrow angle, with the light source almost in the field of view, so as Q.G. said, it would be very difficult, if possible, to solve it with a lens hood.
    I observed it with a 500C/M. I don't know if newer bodies with better antireflection coatings deal better with it.
    Without further testing, the solutions that come to mind are: If you don't want the glare of the light source, as in the case of the OP, move your light source away from the field of view. It really does not have to be that much.
    In the case you are taking an image like the one posted by Q.G. then bring the light inside the image. You will get more glare, but it will look natural.
    I'll do some test, but I suspect that the longer the focal lenght, the less pronouced the effect (speculation)
     
  14. Thank you very much Francisco... I can't quite wrap my head fully around it, but it sure makes a bit more sense now.
     
  15. I have seen this before too. I agree with QG and Francisco that it is an internal reflection of some sort. My suspicion is that it is light coming in from between the body and the film magazine where the darkslide slot is. I can't swear to it now, but I am fairly certain I fixed this once by putting my hand over the dark slide slot. But it might occur on the other side as well. You might try making a little gobo to cover the camera body when you are shooting with a strong light source to the side of the camera.
     
  16. Hmm... I don't know, Stuart.
    I'm pretty confident that it's not that.
     
  17. Stuart,
    What you describe is what happens when the light trap needs to be replaced. In all the examples here, the light source was to the right of the camera, the opposite side from the darkslide slot, so it could not be the cause.
     
  18. You both are probably correct, but wouldn't a light leak through the darkslide slot present on the right side of the film image? The film image is reversed and upside down on the film, but the light leak would be on the left side of the film itself (so to the right of the image...). Am I correct, or just confused? I guess the other suspects I would have would be some reflection through the waist level finder or something like that. For some reason it does not seem to me like a reflection that would come from the light cast by the lens.
     
  19. Stuart,
    The film pane is recessed relative to the dark slide slot, so any light coming through it would need to be on an angled trajectory to reach the film, and it does so starting at about the center of the frame, stretching all the way across to the opposite, 'far' side, with the 'near' side shaded by the step down.
    So a dark slide slot seal leak will show up on the left side of the final image.
    It's not a dark slide slot seal leak though.
    Nor is it a viewfinder leak: the viewfinder is closed off entirely by the raised mirror during the exposure.
    It could not have been a waist level finder leak anyway, because i didn't have one of those on the camera when i produced the example that appears earlier in this thread, but was using a prism finder instead.
     
  20. Ok, I believe you! Your explanation makes sense. I guess the whole dark slide idea makes me vaguely nervous.
     
  21. I did some test about this reflection and got a couple of images. I just put a piece of paper in the place where the back attaches to the body and used a 50 mm wide open on B (T), then used a flashlight to search the spot where the reflection is produced.
    No back mounted here, so we can discard any effect of the dark slide slot
    In the firs image you could see the "double light glare" (I don´t know how to name it) where you see a light glare just at the edge of the frame, then a vertical band and later another light glare
    00Xg15-301785584.jpg
     
  22. Here is the source of the problem, when an extremely bright source of light reflects from this particular part of the body.
    00Xg17-301785684.jpg
     
  23. Just moving the light source inside the frame, more glare but a natural effect
    00Xg18-301785884.jpg
     
  24. How the reflection in the body looks when the light source is just at the edge but inside the frame.

    The only way to check this effect that I can think of, is to take a polaroid proof.
    00Xg19-301787584.jpg
     
  25. Francisco, Thank you. That was incredibly helpful and informative. The mystery is solved!
     
  26. Well done, that man!
    Thanks a lot Francisco!
     

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