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  1. #11

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    Quote Originally Posted by jeroldharter View Post
    I don't think it is lens field curvature because I can measure
    it on the easel with the levels. The lens is a Schneider
    Apo-Componon 150 mm.
    If the field is convex downward I'd expect easel center
    to first come into focus then the corners with a mite
    less extension of the bellows. Has that lens any
    specific best magnification?

    A long shot: By way of trouble shooting you might try
    a red, green, and blue focusing. Dan

  2. #12
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    I did confirm that the focusing is even throughout from center to all four corners on the baseboard. The easels are the problem.
    Jerold Harter MD

  3. #13
    RJS
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    How much 'bowing' do you have? Lately I have been fooling with glass negative carriers, particularly for 35mm and closely inspecting prints I have made over the years with glassless carriers (Beseler 45MX), and I am unable to detect unsharpness in the print made with the glassless carriers. I can see that the negatives are not held flat, and I know glass will keep them flat. But given I haven't been able to detect a difference in the prints I wonder if the glass carrier is worth the bother for 35, at least. For 4X5 I have negaflat, and 2 1/4 the Beseler Negatrans with glass does quite a good job. But this problem is the same as yours; how accurate do you really need to be? If you you can't see a difference in the print, why worry?

  4. #14
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    Quote Originally Posted by jeroldharter View Post
    I did confirm that the focusing is even throughout from center to all four corners on the baseboard. The easels are the problem.
    Good.
    I once had an easel that I beat on with a wooden mallet to flatten it out. The steel was pretty solid so it was not easy.

    Getting back to the issue of depth of field. I presume that since you shoot 4x5 that you are familiar with focusing the view camera using the method of Paul Hansma (http://www.largeformatphotography.info/fstop.html) ? Then you should be able to do the same with the enlarger.

    So, focus on the peak of the easel hump. Note the distance marker on your enlarger column. Then (without touching the focus knob) move the enlarger head downward to focus on a corner. Make note of the distance between the two points in millimeters. Then position the head at the middle point between the two positions. You can use the formula to find your f-stop or I have a hunch you can just use f22.

    If the print is still not acceptable, then either there is a communication gap or the laws of physics have been defied

  5. #15
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    Quote Originally Posted by ic-racer View Post
    ...
    If the print is still not acceptable, then either there is a communication gap or the laws of physics have been defied
    Thanks. I agree. I will try that with a 16x20. Appreciate the advice.

    I feel like using a mallet but I find it hard to do.
    Jerold Harter MD

  6. #16

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    Quote Originally Posted by jeroldharter View Post
    I feel like using a mallet but I find it hard to do.
    If it makes you feel any better about using a mallet, I'm in the position of just having received what was a few days ago a gorgeous near-mint Saunders VT2000 easel. It was improperly packed (by UPS) and manhandled in shipping (by UPS)... the outer steel shell of the easel, especially at the corners, took a beating. The front left corner is so badly impacted that it buckled the steel along the bottom front edge. I feel ill just thinking about it. Fortunately, the top frame, blades, and bed are fine (protected by the outer shell!)

    I'm going to make a claim against UPS for repairs. Far beyond the mallet: It's going to be rather odd going to bodywork shops for an estimate on fixing my easel!

  7. #17

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    Quote Originally Posted by jeroldharter View Post
    I feel like using a mallet but I find it hard to do.
    Support all four corners then stress flatten by weighting
    the center. Might work. Dan

  8. #18
    ic-racer's Avatar
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    When I was dealing with a little hump in my Beseler 16x20 easel, I used a wood mallet and also a steel hammer with a block of wood. I also stood and jumped on it. I couldn't really make any change in it.

    This may not be relevant here, but it is something to think about if you still are having trouble. My little off-center hump in the easel was causing a buckle in the paper. No problem in itself, but I eventually traced a 'blurryness' problem to the fact that the buckle in the paper was shifting and settling out after I closed the easel. Thus causing a problem when closing the easel and hitting the expose button in rapid sequence.

  9. #19

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    I've not read all posts dealing with easels but have
    read a lot of them. This is the first time humps in
    easels has been the issue. No wonder vacuum
    and sticky back easels have some use.

    Clinging bubbles and eddy currents with running
    water slot washers are two more problems supplied
    by the manufacturers of darkroom equipment.
    No wonder a few use still water soaks. Dan

  10. #20

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    Not all enlarging lenses have flat fields. Leicas are the biggest culprits. It is a trade off to keep astimatism under control and they do it with all their lenses.

    The other probably bigger culprit is not having a dead flat negative. Even with a perfect lens, only the center or the corners will be in focus. I have had some sucess matching curved field lenses with non flat negatives. The defects seem to cancel.

    Best results are with a true flat field lens and double glass neg carrier.


    There is no way a 1/8" bow in the center of an easel can put the image out of focus and there is no way you can have a bow that big.

    The double bubble level is ok to get the lens stage to match the base. It is not accurate enough for the lens. You need a lazer device or one of the other products for this. I just use my Peak 10x grain mag at 16x20 and match left/right sides, then forward/backward. After you do this, put it in the corners and all four will be sharp at one time. Then work on the center with a proper lens and glass carrier.

    BTW, every lens is different. So you can`t unscrew one and put another one in it`s place. I know it`s more than you wanted to hear.

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