Uneven tonality in an apparently even scene?

Discussion in 'B&W: Film, Paper, Chemistry' started by jmal, May 23, 2007.

  1. jmal

    jmal Member

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    I have a question or two about the tonality of my prints. When I'm shooting anything with a lot of sky, the sky always appears uneven in its tone, despite the fact that it appears consistent to the eye. Is this just a difference between what my eyes see and what the camera sees? The reason that I ask is that it often appears to lighten when it's next to a darker object/tone. Is this a characteristic of film in general? It doesn't seem to happen in my non-landscape shots. I have attached an example, though it's hard to see exactly what I'm talking about. 35mm Tri-X in DDX. Straight print with no dodging or burning, but cropped to square. http://www.flickr.com/photos/71163977@N00/510294056/ Thanks.

    Jmal
     
  2. pentaxuser

    pentaxuser Subscriber

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    Attachment is simply a box with a X in on my screen. This might be only my screen, of cours but I just thought I'd mention it.

    pentaxuser
     
  3. fhovie

    fhovie Subscriber

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    Causes could include:
    Your camera lens - what kind of distortion does it create? - ALL lenses distort.
    Bromide Drag - negative reaction to specific development proceedures - often mechanical such as agitation.
    Film sensitivity to non visible spectum (UV- IR)
     
  4. Kino

    Kino Member

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    Looks like shutter issues. Are you shooting at the highest or near highest speed of the camera? Is this a FSU (former soviet union) camera? Looks like shutter drag as it starts out and then again when it stops on the other side.

    My Kiev rangefinder, Zenit SLR and Kiev 88 all do this to one degree or another at the highest shutter speeds on a bald sky.

    The reason you probably don't see it on your non-landscape shots is, you aren't running at top shutter speed due to light constraints.

    Try shooting a brightly lighted wall at your top 3 shutter speeds and see what happens on your next roll.
     
  5. Monophoto

    Monophoto Member

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    Jmal -

    I presume that you cropped the image lengthwise.

    A development problem would most likely appear as unevenness across the width of the film - which would then show up as uneveness from top to bottom in a landscape image like you have shown us.

    On the other hand, one can expect that there will be a gradation in sky tonality from the horizon up. So I would tend to accept that the top to bottom variation is real.

    What is of greater concern is the gradation from left to right - with obviously increased exposure in the middle of the frame.

    Two questions -

    1. What camera are you using, and which way does the shutter curtain move in that camera? Does it move from left to right (or right to left), or does it move top to bottom?

    2. What lens are you using? Specifically, are you using a wide angle lens?

    This could be a shutter problem, or it could be the natural phenomenon that the center of the field will receive more exposure than the outer perimeter. But we need to know more to determine which it is.
     
  6. glbeas

    glbeas Member

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    From what I can see the most likely scenario is the enlargers light source has a fall off at the edges, for a diffusion type, or a mismatch in focal lengths between the condensor and enlarging lens with a condensor type, or the wrong bulb in either type.
     
  7. jmal

    jmal Member

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    Camera: Nikon FM2N
    Lens: Nikkor AI 50mm 1.4
    Enlarger: Omega C700 with Nikkor 50mm 2.8 lens and stock bulb

    The shutter was checked in September and was within spec at all shutter speeds. I don't remember the exact shutter speed used in the photo, but I think it was around 1/1000 at f16. Max is 1/4000. The photo was cropped at the top and was not cropped to eliminate a problem; I just likd it square better. The real question in this one is the difference in tonality at the left and right edges. Thanks for the ideas. I'll have to look at a number of prints and see if I find any patterns.

    Jmal
     
  8. nathantw

    nathantw Member

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    I know this is a silly question, but are the corners of the paper that lies on the easel laying flat? I have the same problem with my borderless easel where the paper doesn't lie flat. To fix the problem I get double-sided tape and put it in the corners of the easel.

    Another possibility is that your enlarger isn't set for the correct condenser distance. On my Beseler 23CII I can set the condenser anywhere between 35mm and 6x7. If I set it incorrectly then you can get a hotspot in the middle.

    Well, those are my two ideas. Good luck!
     
  9. Gary Holliday

    Gary Holliday Member

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    My initial thought when looking at the print was a light leak at the edges of the film. I had a bad batch of cheap Eastern European film which done this.

    My suggestion is to shoot some colour transparency film to eliminate any possible enlarger problems. Photograph sky again or something with a continual tonal range.
     
  10. jmal

    jmal Member

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    The easel is a very flat 4-bladed easel, so I don't think that is the problem. It also seems that if there were a light leak on the edges, they would be darker, not lighter. I don't believe my enlarger has any adjustments for the condenser. I am attaching another link for a photo taken at the exact same place and exposure, just framed differently. I did print it a little darker than the other, so I'm not sure it's a fair comparison. This one seems lighter at the horizon and around the tree in particular. The top, which would correspond to the right side of the other image, seems fairly consistent.http://www.flickr.com/photos/71163977@N00/511310878/
    Thanks for the help.

    Edit: the suggestion to shoot some slides seems good. I'll do that after I finish my current roll.

    Jmal
     
    Last edited by a moderator: May 23, 2007
  11. Bob Carnie

    Bob Carnie Subscriber

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    Sanders McNew had a thread going that though not the same result I believe it to be the same cause.
    Insufficient agitation in the initial stages of development.
    Uneven development over flat skys or grey backgrounds*in his case*.
    I don't think this is a exposure problem or camera problem.
    Increase agitation and rotation of the film in the first 15 seconds of development.

    To test for even development photograph a nuetral grey card and work on your agitation and rotation methods. I belive the problem will solved.
     
  12. jmal

    jmal Member

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    Thanks, Bob. I never thought I had a problem with agitation, but perhaps I do. I'll certainly try something different. I usually do 5 twisting inversions per minute. Would you recommend constant for the first 30 or 60 seconds, or just more vigorous agitation? Or both? Thanks.

    Jmal
     
  13. percepts

    percepts Member

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    Take a sheet of paper and expose it to a mid tone on your baseboard with no negative in the carrier using aperture you used for the sample you gave. Develop normally. This will tell you if your enlarger produces even light or not.

    Sky is usually siginificantly brighter towards the horizon due to fact light is passing through much more atmosphere nearer the horizon and haze and atmosperic moisture create the lighter tones.

    Main light source also has this effect to left or right of image and can be dramatically emphasized by printing at higher contrast. Also emphasized when sun is low in sky.

    Could also be your camera lens but I doubt it. Could also be your enlarger lens.

    Shutter? I doubt it.

    Uneven film development also a possibility.

    Uneven paper development also a possibility.

    You will just have to try and illiminate the possibilities by testing methodically.
     
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  15. Bob F.

    Bob F. Member

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    If you have another camera body (or can borrow one) try shooting with that and with your Nikon on the same subjects. Then compare the two sets of subsequent prints. That should tell you if it is your camera or your processing where you need to look closer.

    Good luck, Bob.
     
  16. percepts

    percepts Member

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    take a look at this image and tell me if the two halves are constant tones or does one side have a light gradient towards the join?

    mackieline.gif


    then copy the image and measure the tones with your graphics software and see whether what you see is actually what is there.

    p.s. this image has never been near a camera or any developer of any sort. It is computer generated.
     
  17. jeroldharter

    jeroldharter Member

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    I second the enlarger condenser theory.
    I assume that contact prints don't have the same problem?
     
  18. fhovie

    fhovie Subscriber

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    When you twist a spool in developer - the action is much greater in the center than near the edges where the fluid is slowed down by the rim. I use tank(s) that can be inverted. When I agitate, I invert a few times - more slowly with larger tanks with larger volumes of fluid and then twist a few times so there is no pattern in the motion of the fluid. - Not that this is your problem ... your image is darker in the center which might hint that it is light fall off either from one of the lenses in your process or from the light source.
     
  19. jmal

    jmal Member

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    Thanks for the replies. I'm going to test my enlarger, my agitation, and shoot some gray cards. We'll see if I can either eliminate or reproduce the problem.

    Jmal
     
  20. fschifano

    fschifano Member

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    You are correct of course. It does appear that there is a light gradient near the join, but in fact there is not. Using the dropper tool in Paint Shop Pro, anywhere you measure to the right of the join, the numbers are the same: R=94, G=94, and B=94. To the left of the join the numbers are 0 for R, G, and B. So yeah, your reply does illustrate an optical illusion. Very clever. It is possible that that the OP is also seeing an illusion, but I can't be sure. Truth be told, we know very little about the image. We have no information about the time of day, the condition of the sky (overcast overhead with clearing at the horizon), position of the sun, etc. I don't think it is a development problem, and I really don't think it is a problem with the enlarger's light source.
     
  21. skahde

    skahde Member

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    Can you see this difference in densitiy in the neg? What does the print look like if you turn it by 90° in the enlarger?

    My initial response was uneven developement. About 10% more density at the edges turned out to be pretty normal for me when I got a densitometer and started using it. If you burn in the edges as a standard or print small it is not even a problem and noone will notice it but you seem to have more of a difference than 10%.

    Best

    Stefan
     
  22. JBrunner

    JBrunner Moderator Staff Member Moderator

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    My 2cents are- look to the enlarger first, and then development, camera last. Rule out each in turn. ie the enlarger is easy to test, rule it out, and you know its development, or camera. Rule out the development, that leaves the camera. try a different camera and lens, rinse, repeat.

    My bet is the enlarger.
     
  23. Bob Carnie

    Bob Carnie Subscriber

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    Try mixing your dev with distilled water.
    When you are ready to process , try to think you are sitting in your car with one hand on top of the wheel and one hand at the bottom. Turn the wheel to change the position of the hands , you will notice a distinct twisting motion.
    the first 15 seconds of development is important to get the chems to all areas of a light nuetral grey of either skys or nuetral grey backgrounds, unfortunately if this is not immediate we get uneven grey tones and I think this is definately the problem with the negs you are showing.
    If it was a lens issue either in the camera or enlarger ie lens falloff the problem would be on all sides and would manifest itself as a darkening on the corners , not lightening.

     
  24. jmal

    jmal Member

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    Bob,

    I already use distilled water for all of my chemicals. My agitation method also involves a twist as well as inversion, very similar to what you describe. I will really concentrate on beginning the agitaton as quickly as possible and continuing it a little longer initially. Hopefully this helps. Also, I can see how light fall off in my camera lens would create darker edges, but wouldn't fall off in the enlarger lens create lighter edges? However, I do agree that it would be more uniform--a least I would think.

    As for the conditions, it was a moderately sunny day and the sky appeared to be a consistent light blue. Around 1 o'clock. I don't remember exactly where the sun was at, though. As the problem occurs on both sides of the print, I'm not sure it has to do with the location of the sun. I could be wrong; light behaves in strange ways. The shot was taken in the Flint Hills of Kansas, so there is not much else around to cast obvious shadows. That's about all I can think of in terms of the conditions.

    Jmal

    Jonas
     
    Last edited by a moderator: May 24, 2007
  25. PepMiro

    PepMiro Member

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    I think the most probable cause is uneven projection of the enlarger.
    You could try to print a paper with no negative with an exposition time enough to print a middle gray (more or less) an look the result if grey is uniform or not.
     
  26. Bob Carnie

    Bob Carnie Subscriber

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    Jonus
    you would really see the fall off on the easel and if you take out the neg and just print to a nuetral grey you will see immediately if it is the enlarger. Prepmiro is right it would be very obvious if this is the cause.
    you are correct the falloff would lighten the edges but this really looks like a familiar film dev problem. critical in the first 15 secs.