Exposure or developing issue?

Discussion in 'Large Format' started by dirk-san|1, Dec 3, 2004.

  1. Hello, I am fairly new to LF, using a 4x5, currently using TXP 320. The other day I shot and forgot to stop down the lens, but I realised it and made a second exposure. After processing I found that the negative overexposed by two stops looks a lot better than the "correctly" exposed one. I know that box speed is not always real speed, but two stops difference seems a lot. Looking at another pair of negatives where exposure is one stop different, I cannot see any difference between the negs whatsoever. This is also very odd. Maybe my processing is to blame. I am processing in trays with constant agitation on a self-built frame that holds 8 sheets of film fixed in the tray, similar to Phil Bard's frame. I am using Xtol 1:3, which is quite diluted, maybe too much? Anyway, looking at some of my previous negatives, I find a lot of shadow areas that when scanned, strangely enough, look like flare. It happens sometimes, but not always. I am not sure whether those two things are related though, but I have a feeling they are because I never get the fog on well-exposed negs. I am really stumped by this, can anyone give advice? Dirk
  2. I would suspect development.

    Look at all of the negs that were developed in the same batch and see if the 'flare' is in the
    same part of the frame.

    Xtol 1+3 isn't recommended in general..lots of people still use it though. There is a
    minimum recomended amount of Developer for a given amount of film. 8 sheets of 4x5 is
    a lot of film...

    Don't change too many variables at once or you will never figure it out!@

  3. Thanks, yes, I consider 4 sheets as one 35mm, thus 100ml of developer and 300 of water.

    It doesn't occur in all pictures of a batch, although if it occurs it is always in shadow areas,
    and often in the lower part of the frame.

    Again, that shot I did twice, same scene. The "correctly" exposed shot shows very slight
    signs of the phenomenon.

    I am also using shift movements, if there's a connection.
  4. I also pre-soak, if that's relevant (because I had cases of film sticking to surfaces).
  5. Perhaps there's something wrong with the scans, and nothing wrong with the negs.

    Have you tried proofing or printing the negs "conventionally"?

    Are these "flare" areas visible when you inspect the negs?
  6. Lucks for me more like fogging from light. Could it be thad the camera back was not fully light tight because you did not put the holder 100% at the right place, for example?
  7. I agree with Armin -- it looks like fog to me.<P>And Xtol @ 1+3 -- I know dozens of people who use it (actually from the day Xtol was introduced -- they swear by it (as do I for both 35mm & 120 -- I don't shoot 4x5). <P>The only thing you MUST be careful of is the 100 mls of stock per 80 sq inch's of film recommendation -- something you're doing. (just out of curiosity -- is the 400 mls of solution you're using completely covering the negs and is the stock fairly fresh and well stored).<P>I think you should perhaps make some contact prints. If the problem shows on them then it's time to do some carefully recorded test shots of the ol' brick wall.
  8. Hello Dirk,

    It looks like a light-strike to me. when I first got my LF camera I used to get similar areas of fogging. It turned out that sometimes I was careless pulling out or reinserting a stiff darkslide - I was forgetting to keep the holder pressed tightly against the back now and then while I was struggling, so the problem was intermittent. I now keep my thumb squarely pressed against the holder when withdrawing/inserting the slide, and the problem has gone.

    I used to wonder about the difference in exposure on similar negs, too. Then I got a small calumet shutter tester and examined all my shutters. Most were out at top and bottom of the scale, the better newer shutters by a third or half stop, but some older ones were a stop out. If I took two exposures, varying the time/aperture between them but keeping (I thought!) the same relative exposure, my calcs were often well out, particularly at lower shutter speeds.

    I have made notes of the true speeds of each shutter, so this isn't too much of an issue now. Worryingly, the shutter tester showed that some of my older shutters had intermittent faults, giving irregular times - short of a CLA, I can't do much to remedy that1

  9. "After processing I found that the negative overexposed by two stops looks a lot better than the "correctly" exposed one. I know that box speed is not always real speed, but two stops difference seems a lot."

    Not really. My experience, FWIW, is that Tri-X and some (not all) other b+w emulsions are unforgiving of underexposures, but can take overexposures with ease. I always rate Tri-X 400 roll film at 200 and Bergger 200 4x5 sheets at 100, and even then I err on the side of overexposure when dialing in aperture and shutter speed. I get much better shadow detail that way, without losing highlight detail.

    If it matters, I develop both in Rodinal, 1:100 at 13 minutes for the Tri-X and 1:50 for 12 minutes for the Bergger. (I've not worked with Tri-X 320 sheets, but I assume it is a different beast and my roll film recipe would not work for the sheets.)

    Sanders McNew (www.mcnew.net)
  10. TXP pro is really about 160. If the development time is cut 20%, 80 could get a nice neg with lots of shadow detail and printable highlights.

    I think you have a light leak in the camera , upper left corner. You need to solve this before proceeding. Holder might be warped or the rear standar warped or the bellows not attaching properly.
  11. Thanks a lot for the answers everyone. No, I haven't proofed the negs in a darkroom yet, and also suspected the scanner, but I am starting to suspect a light leak. I have looked at the negs again, and yes, there is certainly a lack of contrast in certain areas, indicating fogging. Now the question is where from? My holders are numbered and I keep track. The effect doesn't seem to be related to certain holders. My handling of the holders could certainly be an issue. I will try the technique suggested by Neil, although the seating of the holders is quite firm, if done correctly. Shutter should be OK, as the lens is new (but you never know). My greatest fear is that what Ronald said is true, a problem with the camera. But then why is it intermittent? Shouldn't a camera fault affect all images? What's particularly strange is that shots of the same subject can be different, really indicating handling error. But to be sure, what kind of testing should I do? Like inserting a holder, removing dark slide, maybe moving the camera or a light source around the seams and develop that sheet? My exposure/developing question really seems to be a different issue altogether. Maybe I am actually rating TXP at 80 without realising. The joys of LF... just when you thought you had some experience taking and processing pictures, it is all back to square one. :)
  12. TEST 1:place camera without lens and bellows fully extended in a dark room. Using a small flashlight such as a minin mag adjusted to spot at about 2 inches, run the full length of the bellows along all cornors and sides. ANY hint of light is a leak! Now insrert a film holder into the back and shinning the light from inside the camera observe the outside for any hint of light comming from around the holder. Do this for both sides of all holders. Now close the camera partially, recheck the holders as before and pull the darkslide, and check for light coming thru the darkslide slot. Try the light both from the inside and outside of the slot. Next put a lens on the camera and from the inside test for light leaks around the lens board(s).

    Test 2: Inspect all holders at the side to top and bottom seams for looseness or gaps. If you can get a razor blade edge in the gap then it is a potential leak. I filled such gaps on my 8x10 holders with RTV black silicone sealant.

  13. I think you have a little light leak coming from somewhere. If it's consistantly in the same place, perhaps a pinhole in the bellows that fogs at certain focal points? Maybe a little fog in your processing method?
  14. Thanks again for the follow-up responses and advice. I am really grateful for them.

    I will do these tests and also double-check the processing stage to try and find the culprit.
  15. Results!

    I did the test with the flashlight/torch as explained by Charles Monday (thanks again), and
    you were all right, it is a light leak and has nothing to do with processing or exposure
    (well, it is exposure but...).

    It appears that the bellows was once before glued by a previous owner to the frame that
    attaches to the standard - badly. This glue seems old and dry and a small slit had opened
    up. Since the bellows can be attached in 4 different ways (top/bottom/front/back) the slit
    would wander leaving me clueless, and since the lens is short-ish (120mm), rise and fall
    would put enough tension on the bellows to open the slit a little.

    I have removed the bellows from the frame part wherever the adhesive seems porous.
    Question now is what glue to use to do the job properly? Frame is plastic, bellows artificial
    leather-ish type of material. Camera is a Cambo SC II, actually.

    Super-glue seems is my initial thought.
  16. Sorry, one more: and how to remove the residues of the old glue?

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