Cause of enormous flare?

Discussion in 'Large Format' started by mike hardeman, Dec 28, 2004.

  1. After purchasing a used 480mm Schneider lens with a Copal shutter for my 8x10, I was surprised to find the enormous flare in the middle of some of my images. The first one was taken at about 8:30 AM at Sequoia National Park under a clear sky, but the sun had not hit the trees or the camera at this point. It's about a 2 minute exposure at f64, spot metered. The second one was taken the evening before in much lower light, a 10 minute exposure at f 64. I'm trying to figure out the source of this anamoly. I've checked the lens, shutter and lensboard for light leaks. The camera does not leak, either, brand new Tachihara. I have used other 480mm Schneiders with no problems. I did not use any filters with either version of the lens. Any ideas???? Thanks.
    00AaFo-21108384.jpg
     
  2. Well, I can clearly tell you that you should not have used the flash with the first image! I cant see what your talking about. Do you have a scanner? or maybe just take the image without the flash.

    Sun flare does NOT always have to come dirrectly from the sun shinning INTO the lens.

    Ryan McIntosh
     
  3. It almost looks as though you have a pinhole in the darkslide. That is a pretty strange looking spot, don't know how you could get it right in the middle without their being something obvious with the lens. No holes in the lensboard, right?

    Isaac
     
  4. Does not look like a lens problem to me. Too intense in a small area.

    IMHO it is a light leak. Could be a small hole in the slide, or a small hole in the lens board.
    Or it was caused during loading/unloading the holder.
    Who processed it? Could have happened then also.
     
  5. Maybe the lens was stopped down to f32 or more to focus and you pulled the darkslide before re-adjusting for exposure causing a double exposure? Been there..done that.
     
  6. A shutter problem? The shutter does not close completely? In the shorter exposure the effect would be larger than in the longer exposure due to the fact that the light leak is stronger in brighter light. Definitively some sort of light leak.
     
  7. I think that Ryan is the only one who is on the right track here. No holes in the holders, the shutter is tight, not a processing problem. The flare happens, even in the second image, but not as intensely. I think shading the lens might help, as it becomes more pronounced as you point the camera towards more ambient light.
     
  8. Michael,

    If it was flare, you would see it while composing and focusing.

    Think about it. Flare would only happen for the same amount of time as your exposure. So if it was that bright in the final image, (relative to the rest of the image) you couldn't miss it while focusing. So this must be happening for a longer period of time than your exposure. Therefor it can't be flare.

    Nor can it have anything to do with the shutter, since a shutter that didn't close all the way would result in a blurred image and over-exposure.

    Have you had this happen with film in different film holders?

    What type of film are you using? If you're using Readyloads the problem could be in the holder.
     
  9. If he was doing a 10 minute shot, then he would NOT have been able to see any flare on the ground glass because clearly the ammount of light was very soft when making the image.

    A light leak in the lens board or anywhere in the camera, would have slightly fog the whole film, not just a small exact spot right in the center. Because the lens was open more for the second image, there would of been MORE flare in the second, you would think.

    I would recommend just going out in your backyard and make a negative and see what happens. Make a few negatives with the bellows and lens extented to different lengths. I had this problem with a old Ektar lens on a 4x5 Graphic. The closer my lens was to Invinity, the worst it was, but when I would extend the lens out to focus more closly... it would go away. It was a problem with the possition of the lens and I belive reflection inside the camera that was causing a weird spot on all my film.

    Ryan McIntosh
     
  10. Ryan,

    I did point the camera indoors at a bright source, while having the ground glass removed, and noticed that a lamp above the lens was producing a reflection, or flare, within the rear element of the lens, so I suspect this IS a flare of some sort, but not enough to become clear on the ground glass.

    The first image in this posting is the WORST manifistation of the flare. The flare is actually present in the second image, but to a much lesser degree. I think the reason for this is that the sun was more behind me and had already set behind the mountains. In the first image, the sun was higher in the sky, and more to the right and front of the camera, thus producing more of a flare.

    I think exposing some chromes outside would be a good idea, both WITH and WITHOUT extra shade around the lens, to see what happens.

    Besides a flare, my other theory is that the light reflects from the film, back to the rear element of the lens and back again, but if that were the case, it would do it to the same degree in all shots.

    At any rate, I don't understand why this happens on this particular 480mm because I've used the same model lens with no problems before.

    Again, this is NOT a problem with film holders. All the holders are in excellent shape, and the same flare shows up to one degree or another, regardless of which holder I'm using. I have not quite ruled out a light leak, but, like you said, they tend to fog entire areas of the film, without any focus.

    Mike
     
  11. "If he was doing a 10 minute shot, then he would NOT have been able to see any flare on the ground glass because clearly the ammount of light was very soft when making the image."

    If light levels were so low that he couldn't see that bright a flare, he couldn't have seen the image to focus. So, unless this is one of those new autofocus 8x10 cameras, it ain't flair. It's a light leak.
     
  12. I'm sorry, but that last comment makes NO sense at all.

    Yes, it was a 10 minute exposure, but at f64. My light meter gave me a "4" and I was shooting Velvia, pushed one stop to 100. I had NO trouble with seeing the image on the ground glass. There are no light leaks in this camera. I've used other lenses with it with no problems, it's a brand new camera.
     
  13. The first one ... under a clear sky, but the sun had not hit the trees or the camera at this point. Without direct rays from the sun reaching the lens, I have a hard time envisioning flare in the lens causing an effect as strong as seen in this photo. One time I got a flare image of the aperture from a cloudy sky which filled half of the view of the lens, but the effect was much, much weaker than this and the polygonal shape of the aperture was evident.
    A light leak in the lens board or anywhere in the camera, would have slightly fog the whole film, not just a small exact spot right in the center. I have seen other examples of light leaks that actually form an image. A small light leak will function as a pinhole and make a faint image. If this is a light leak, the hole would have to be larger because of the intensity of the spot and thus it wouldn't form a good image.
    I agree with some of the others. The first example has such a strong amount of "extra" light that, if the extra light had been present while composing, Michael H. would have seen it -- the light spot is brighter than the image, so if he could see to focus, he would have seen the light spot. The other possibilities are that somehow the extra light changed during the exposure, or that it was added at another time.
    Are the examples full crops of the films? Are the spots of extra exposure exactly centered? With a light leak, it would be hard to explain exact centering.
    As a test for a light leak, I suggest focusing the lens, then closing the shutter and removing the dark slide from the holder. Next, move the camera around in direct sunlight so that sunlight strikes it in many ways. Finally, develop the film without ever having made an exposure through the lens.
     
  14. Assuming you didn't see this anomaly while focusing, how could it have come through the lens?

    In other words, if it came through the lens, why didn't you see it?
     
  15. Indeed. If it was flare at f:64, you would be able to count the aperture blades.
     
  16. "brand new camera" does not always equal "no light leaks."
    My guess is that with the 480mm you're at greater extension which is
    stretching the bellows and causing it to gap somewhere. (pay particular
    attention to all seams and attachments)
    Let us know when you find it.
     
  17. I agree that it is possible for a new camera to have light leaks. However, I have shot with this camera and a 500 mm lens as well with no problems. I have also double-checked for light leaks in the traditional manner.

    However, there IS the possibility that a leak might originate with the lensboard, although I have checked for that as well.

    I like the idea of the test without doing an exposure. That might be it. I will do one test in that manner and another one using "barn doors" around the lens, to see if that cuts down on the flare.

    The top image is full-frame, the second one has a bit of the top and bottom cut off, but is more or less centered, with the full width of the original frame. Again, the bottom image DOES have the flare, but to a MUCH lesser degree.

    Some of the images "in between" simply look more exposed in the center part, as if a center graduated filter may lessen the problem.
     
  18. Peter is right- it's not flare. It's a light leak of some sort.

    b.
     
  19. I have a couple of questions that may sound silly, but I ask due to experience. Is the shutter new or used? What was the temperature when the shots were taken? Have you taken any shots at faster speeds, say 1/30 ?
     
  20. The temperature was very comfortable, in the 50s for both shots. I don't shoot anything, ever, that's less than a 2 second exposure.

    In regards to so many people saying it can't be a flare, it must be a light leak, I must ask how you know that? If it's a light leak, then why doesn't it happen with every shot? I'm not ruling a light leak out, and it doesn't LOOK like a flare, if I didn't know what I know, I'd say it was a leaky film holder. But, if it's a leak, then why is it CENTERED in the picture and perfectly circular? What would produce a leak like that in some pictures and not in others?

    Thanks for everyone's thoughts...
     
  21. I don't think it's a light leak. I've had light leaks from sun shining into film holders with the dark slide pulled, I've had light leaks from pin holes in the bellows, I've had light leaks when I didn't properly replace the standard bellows after using a bag bellows, and I've had light leaks from a tiny hole in the lens board (caused by the cable release thingy on a Linhof board falling off and my not thinking about the effect of the resulting hole in the board until it was too late). None of them produced results that looked like the first photograph.

    It's true, as others have said, that flare isn't caused only by direct sunlight striking the lens. Flare is actually more of a problem when photographing in bright diffused light because you can't use your hand to block that kind of light. However, I wouldn't think the flare caused by that type of light would be as stong or as directional as the flare in the first photograph. So I don't know exactly what the cause is, maybe a defect of some sort in the lens, maybe light bouncing around inside the bellows, who knows, I just feel reasonably confident that it isn't a light leak in the lens board, film holder, or bellows.
     
  22. We know it's not flare because flare is reflected light from the glass to air surfaces within the lens. It isn't light that passes through the lens without bouncing around, so to speak. That's why you can see either the aperture blades or the subject with flare.

    For instance, if the sun is causing flare, and the sun is within the image, you'll see the sun in the image, just not positioned where it's supposed to be, and not as bright as it should be, but usually 180 degrees around the axis of the image from where it's supposed to be, along with the actual image of the sun positioned where it is supposed to be, and as bright as it is supposed to be.

    If the sun is outside the image, it can still cause flare. If the sun is at 11 o'clock but outside the field of view, it can flare and put one or several reflected images of the sun on the film, in a line extending from the center of the image, towards the 5 o'clock position.

    But they will be images of the sun, focused just as sharply as the sun would be if the sky is focused at infinity. There would probably also be reflections from the aperture blades, unless the aperture was fully open.

    But unless there was an extremely bright source of light that was very out of focus, you would never get flare that looks like the anomaly in your images. That anomaly isn't in focus. If you get flare from a light bulb, you will often see the filament in the bulb. Your fuzzy bright area isn't an image of a thing, like the sun or a light bulb. Therefore it isn't flare.
     
  23. Is it possible that it might be a processing problem? We seem to have eliminated everything else?
     
  24. Michael,

    Is there some exposed metal in front of the glass, like a ding, reflecting light at an odd angle?

    best,
     
  25. You know, there actually is a small ding on the back element ring. I would not think it was large enough to cause this problem, but right now, I think anything is possible. Here is a picture of the rear element.
    00AaqA-21121784.jpg
     
  26. Oh, and processing is not the issue. Nor is the film. The film has 9 months before the process-by date, and is all from the same box. The processing was done by the same lab at the same time. AND there were several very good shots in that same batch, shot with other lenses.

    I believe that is caused by a defective element, that is overexposing the center part of the picture. The reason it looks like a light leak is because this particular picture is so extreme. Several other shots simply appeared to be a couple of stops over-exposed in the center. The outlying areas of those shots were perfectly exposed with no evidence of any problem.
     
  27. I once had a lens which developed moisture condensation on an interior element when I took it outside in the morning. Moisture on the front element evaporated right away, but it took a long time for the interior moisure to disappear.
     
  28. Well, crazy as it sounds, I had the exact problem once upon a time in a smaller camera.
    Same exact spot, everything. All elimination testing pointed to the lens. Maybe it was or
    was not flare, but it came with a particular lens (relatively modern) and that lens only.
    Sunshades, cleaning, even exorcism - nothing worked. The solution was elegant and
    totally effective. After careful consideration, we determined that screwing around with
    defective junk was a much bigger mistake than buying the junk in the first place, so we cut
    our losses and threw the lens off a bridge over I-95. The problem has never returned, so I
    firmly believe that we hit upon the correct cure. Hope this helps. (PS: This is not a goof, I
    am serious about having had this problem.)
    Jon
     
  29. Weird. More weird that you wouldn't see such an obvious spot while focusing/composing the shot, unless it only shows up when well stopped down. Setting up with a bright enough subject so that you can see the GG image at f64 might be an idea. Does the contrast seem low when focusing?

    A bellows pinhole would tend to overlay an image on the film ("WHY is there an image of the window over my still life?"), and unless you have a light with a diffuser panel mounted with the camera, this doesn't look like that.

    That ding might have something to do with it, if the lens is tossing light that far out the edge and the ding is on the bottom (reflecting sky?). Try a shot with the whole thing mounted upside down if you think that might be it.

    Light reflecting from the film, back into the lens, to be reflected and sent back to the film in an out of focus spot is an unlikely possibility, as would be some sort of light leak through the shutter. Hmm, there's no chrome or other shiny/reflective surfaces on the inside of your camera, are there? Just considering ways that it would be possible to intentionally produce this effect, the right shiny plastic curved surfaces could make it happen, and only with one lens focused at the right distance.

    The thing that really bugs me about this is that it looks an awful lot like the kind of spot you'll get if you try taking your picture (with flash) in a mirror, and that the spot itself seems taller than wider AND appears to have it's own flare, which makes it look even more like the mirror-flash thing. Odds are that you don't have some wise guy sticking a flash directly (and perfectly centered every time) in front of your lens while the shutter is open.

    There doesn't seem to be a color cast to the flare spot, more like an overexposed area - or an average of the scene? Too bad you can't see it on the glass, else you could wave colored paper around to see where it's coming from.

    How about this - look at the edges of the internal elements, do they have the proper blackening in place? Or did some previous owner decide that "schneideritis" was unsightly and that the offending blackening should be removed? This might create a large reflected diffuse source within the lens that could conceivably end up directly centered on the image. I knew an eyeglass wearer that had a vaguely similar problem with a high correction on large lenses. If you can see much light through the blackening it's probably inadequate. Just another idea, I'd be alarmed too.
     
  30. I am sceptical of most of the guesses here, but one may turn out to be right. I expect that the cause won't be determined unless Michael H. can recreate the problem -- then he can start varying one (or a most a few factors) at a time and see which correlate with the problem. It may be that the cause is so oddball that Michael H. won't be able to recreate it, which won't be so bad because then he can go back to using the lens.

    I can't see it being from a defective elements that refects light forward, and the another reflects it back to the film. Then you would see the problem in most exposures, plus it would have been visible on the ground glass for the first photo.

    Which Schneider lens is this? It is single or multi-coated?

    The ding doesn't look big enough nor positioned to cause this problem, but you can experiment by covering it with dull tape or paint.
     
  31. Not to muddy the waters further, but is that "flair" at the top right corner of the first image?

    To tell the truth, on my screen it looks like there's actually two bands of flair streaming diagonally down from both top corners to form the center hot spot.

    Unfortunately, even if that's the case, I'm not sure what it would tell you except that the symmetry of that kind of formation would suggest some weird kind of bellows flair to me. Perhaps a strange combination of that particular lens' image circle and bellows extension? I guess you could test this by taking a couple different shots in constant light conditions but with shifted focus so as to see if different bellows lengths changes things.

    I dunno, it's a puzzler!
     
  32. I too noticed the star shape of the spot. That looks like the diffraction pattern of a rectangular hole.

    Open up the aperture and shine a bright light through the lens. Make sure the shutter closes all the way. How cold was it when you shot? Perhaps the shutter gets a little sticky when cold and leaves a hole open.

    Just WAGs...
     
  33. Come on guys, it's "flare," not "flair."
     
  34. Who cairs?
     
  35. I'm going to have to go over all of these theories again, so bear with me for a day or so while I do that. I'll also post one of the other images that went bad, for comparison. Again, the temperature at both exposures was in the upper 40s to mid 50s, so I don't think that it's an issue. After I post a second picture, it might make more sense.
     
  36. I must admit that I haven't read all 2 million responses here but I had a thought. Well, actually 2.

    Thought #1. It is an accidental double exposure. (Probably not but it was a thought.)

    Thought #2: Because this is in the exact center of the lens, it might be a shutter that is intermittenly (sp?) not functioning correctly. These shutters open from the center and close back to the center. I know I am splitting hairs here but the center of the lens does expose the film ever so slightly more than the edges. Therefore I think it might be a shutter that is not closing properly every time. Obviously it is only happening every once in a while so there is probably no way to know for sure but it wouldn't hurt to have the shutter cleaned and lubed.

    Just my thoughts,
    Happy new year to all,

    Randy
     
  37. Regardless of how much the shutter is opened, all the light passing through it is focused. The shutter is right next to the aperture. So a shutter that's slightly open is really no different than a small aperture opening.

    If we assume that Michael removed the dark slide after focusing the image and replaced it before moving the lens and/or camera, a slightly opened shutter would have only one effect: to increase the exposure.

    It would not increase the exposure just in the center of the frame, just as an aperture of f:64 doesn't result in a greater exposure in the center of the frame than shooting wide open would, relative to the rest of the frame.

    In fact, the opposite is the case. The smaller the aperture, the larger the image circle, and the less the light falls off in the corners.
     
  38. Don't know, but I had an experience with a similar "ghost" on a chrome and it turned out to be a light leak from a opening on the front of my lensboard for a packard shutter tube. Taped it off inside the bellows and the "ghost" left!
     
  39. How's this for a theory, Michael:

    The ghost was created when your stack of film was exposed to light due to a leak in a film box or a lapse in handling. The lighter second ghost was made by the light that passed through the top sheet of film to the second sheet.
     
  40. Sorry, doesn't wash.

    I did some test shots and confirmed that shading the lens gets rid of this problem to a great degree. The tests ruled out light leaks because I covered any possible source of a light leak and still had the problem on that shot. But when I completely shaded the lens (to a large extent than normal), the anomoly subsided a great deal (not completely).

    The film holders are in top shape, the camera is new, the lensboard tight. THERE ARE NO LIGHT LEAKS. I think the tendency to call it a light leak is from the extreme nature of the overexposed portion of the first image. I should have displayed an image where the overexposure was not as intense. In those images, it really looks like an overexposure, whereas the one I chose looks like someone drilled a quarter-size hole in the film holder.
     
  41. Michael,

    How do you explain the first image? Why didn't you see the anomaly while setting up the shot? It seems to me that you couldn't possibly have seen it, otherwise you would have done something to prevent it.

    So, since you didn't see it, how could it have happened while making the exposure?
     
  42. I think one of the reasons is the fact that the film is Velvia and pushed one stop, making it more contrasty.

    Another reason is that it was a long exposure, 2 minutes.

    I've tried very hard to see this flare in the ground glass, it simply does not show up.
     
  43. "I think one of the reasons is the fact that the film is Velvia and pushed one stop, making it more contrasty."

    Say wuh? Michael, I'm sorry, but that's ludicrous.

    "Another reason is that it was a long exposure, 2 minutes."

    How would that effect the anomaly? The trees were exposed for the same two minutes. The background was exposed for the same two minutes. The relative values of the trees and background and anomaly would be the same for a 2 second exposure as for a two minute exposure.

    "I've tried very hard to see this flare in the ground glass, it simply does not show up."

    Therefore it isn't flare.
     
  44. Thanks. Maybe "flare" isn't the right word, perhaps "glare" is a better term. Whatever it is, it's reduced or eliminated by shading the lens. Light falling on the outer element of the lens is refracted in such a way as to produce an overexposure in the center of the picture. I'm sorry if it doesn't show up in the ground glass, but that's the way it is.
     
  45. I'm just having a very hard time imagining how something could show up on film, but not on the ground glass.

    It would be one thing if the phenomenon only occured at a small aperture and you closed down to that aperture without checking the focusing screen for the effect. But since you would have checked the screen after closing down to shooting aperture in order to be sure that you got into focus everything that you wanted in focus, and since you didn't see the phenomenon then, it's a bit of a puzzle as to how it could have gotten there.
     
  46. Over Christmas I picked up a 1951 copy of "Lenses in Photography" by Rudolf Kingslake (then Director of Optical Design for Eastman Kodak). I just got to Chapter VI - The Brightness of Images - and therein are two example photographs that look just like yours. His explanation:
    "Flare Spot - As shown in Fig. 68, any doubly-reflected light beam from a lens will cross the lens axis somewhere, and at that point it will form a well-defined image of the iris diaphragm itself. If this happens to fall close to the film plane, it will cause a more or less sharply-defined image of the iris, superposed on the middle of the picture (Fig. 71). This may be easily distinguished from the out-of-focus ghost image referred to in the last paragraph because it is precisely central, while any kind of ghost image moves about as the source is moved in the field.
    If several of these multiply-reflected images of the iris diaphragm fall close to the film but not in focus upon it, their intensities may nevertheless add up to a considerable amount of light, causing a "flare spot" in the middle of the picture (Fig. 72).
    A flare spot, or an in-focus central diaphragm image, is visible only at the smallest diaphragm openings, because it is usually highly magnified and at the larger diaphragm openings the image falls entirely outside the picture area. Moreover, the brightness of the diaphragm image is independent of the size of the iris, while the brightness of the background increases as the square of the iris opening; hence as the disphragm is opened, the background brightness rapidly and soon drowns the faint iris image entirely. The color of a flare spot is, of course, the average of the whole scene.
    A flare spot is particularly unfortunate when stray light reflected from shiny regions in the lens mount is also present, because the two sources add up and may lead to a serious situation. Indeed, many cameras have been entirely cured of their flare spot troubles by an adequate blackening of the interior of the lens barrel."
    Whew! Hope this helps.
    Chauncey
     
  47. That's what I said.


    What?
     
  48. Chauncey,

    Thanks a bunch for that. I think you're analysis is by far the most intelligent and closer to what I believe is going on.

    One thing should be noted: the test shots (not shown) that I did last week confirm that this problem occurs at its worst when the lens is not sheilded. There need not be (as is the case with other lenses) any DIRECT sunlight on the outer element to see this problem. That is typical of a FLARE.

    In this case, what is seen in all of the troublesome images is merely an overexposure of the central area. You do not see the typical image of the leaves of the iris, as is the case with a flare.

    So, even in the best of situations, you have an area that is slightly over-exposed in the middle. When the light source is directly behind the camera, this over-exposure is at a minimum and is barely detectable.

    I wonder how practical it is to blacken the inside of the barrel of this lens.
     
  49. Michael,

    For the last time, if it's flare, why didn't you see it when viewing the image on the ground glass?

    Perhaps there's something you haven't told us? Perhaps you didn't look at the image after you stopped down? Hmmm?
     

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