Beseler 23C - Focus not flat

Discussion in 'Darkroom Equipment' started by Worker 11811, Jul 3, 2010.

  1. Worker 11811

    Worker 11811 Member

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    Have an old Beseler 23C. The old, "Universal Color" type.

    I can not get the thing to focus evenly across the easel.

    If I focus at the center of the image, the edges are out of focus. Mostly at the top, left and the bottom right.

    If I focus at the top, left, the center can be brought into focus but the bottom right will be out and vice versa.

    I can fiddle and fiddle with the focus but, eventually, I can get it to be close but not perfect.

    I have aligned the X-axis pretty well. If I fiddle with it, I can get the left and right sides to focus pretty darned close to the same point.

    I can't figure out if there is a Y-axis adjustment.

    I have tried putting several pieces of photographic paper between the negative holder and the bottom of the stage. If I put 6 or 8 slips of paper in there I can get the thing to focus pretty close to flat. But putting that much shim material in the trap every time I want to make a print will be a PITA in short order.

    Does my lens have some kind of astigmatism problem? Is there some way to ensure alignment of the lens on the lens board? Is there an adjustment of the front-to-back alignment that I'm not able to find?

    I have heard that this vintage of Beseler can be cranky in the focus department. Is this just something I'm going to have to live with?
     
  2. 2F/2F

    2F/2F Member

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    Hi,

    The negative stage must be aligned with the easel. Assuming your easel is completely level (which it should be, if it is not a battered speed easel or a bladed easel with missing feet), you can use the baseboard as well.

    I don't know enough about that particular enlarger to tell you where the alignment hardware is...but I am almost certain that it must be there. Even my cheesy Omega B22 was align-able two ways (and believe me, I had to align it OFTEN), and the Beseler is a better enlarger in many ways.

    I am 99.9 percent certain it is not your lens.

    The big thing that will throw Beseler enlargers severely out of alignment is if the left and right gears end up at different points on the left and right columns; a "jumped" tooth on one of the two column racks. Omegas, Dursts, DeVeres, etc. do not have this problem, as they use only one column. However, you already have achieved alignment in this axis, so I think you are OK. It would also be very easy to see this with the naked eye if it was happening.

    As I said, I do not know the 23 models well, but the 45 models have a lens stage tilt, which is actually a great feature to have. I have used this feature quite a bit when shooting with cameras that have no movement or limited movement (such as my Speed Graphic, which has tilt, but no swing). It is possible that if the 23 has this feature, the lens stage is not level to the film stage. Again, this would be along the axis you have already successfully aligned, but you definitely want to look at it.

    What you need is the instruction and/or service manual, which I am sure you can get either second hand or from Beseler proper.

    Good luck. It is a pain, but entirely worth the effort, so stick with it until you get it right.
     
  3. Vaughn

    Vaughn Subscriber

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    Unless the earlier models are different, there are two axis of adjustments, both below the lens stage. One that allows the lens to swing left and right, and the other is a screw and nut that adjusts how far the head tilts toward the column.
     
  4. Worker 11811

    Worker 11811 Member

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    I only have to turn the focus knob a little bit to get the focus to change.

    The entire distance the carriage moves up and down the focus rails is less than a 1/32 of an inch. I put the top/left in focus and marked a pencil line on the rail then focused the bottom/left and marked another line. Both pencil lines touch. The distance to focus one part of the image vs. the other is about the width of a pencil line. (Freshly sharpened.)

    Vaughn, are you talking about that "bumper stop" underneath the back of the carriage? I messed with that but it didn't seem to make much of a change. I'll have to look into it some more.

    Maybe I should move the head up to make an 11x14 blow-up and align that. Theory being that, if that size is in alignment, the smaller sizes should be a piece of cake. Right?

    Here are some test prints I made with SMPTE test film I brought home from work.

    [​IMG]

    (Full Size)
    http://homepage.mac.com/randystankey/.Pictures/B23C/RP-40.jpg

    [​IMG]

    (Full Size)
    http://homepage.mac.com/randystankey/.Pictures/B23C/Clips.jpg

    Yeah... I've got OCD about focus. :wink:
    It's an occupational hazard. When you have 200 paying customers screaming because their movie isn't in focus, you tend to get a bit jumpy about it. :wink: :wink:
     
  5. gkardmw

    gkardmw Subscriber

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    I use to be perplexed about why the lens does not have an adjustment independent of the rest of the head to adjust it from front to back. What I do now to align the lens from front to back is to loosen the screws on one of the two plates that hold the lensboard. This allows the lens to be adjusted either higher in the back or front depending on what pair of screws you adjust. Made all the difference in the world to me.
     
  6. Worker 11811

    Worker 11811 Member

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    I think I've found the source of the problem.

    Reasoning from this point: "The center line of the lens must be perfectly perpendicular so that the focal plane of the lens is perfectly parallel to the film plane."

    Investigation of the lens board and the way it aligns, I found some slop in the screws that hold it in place and allow the user to align the X-axis. If those parts and screws are not aligned and tightened properly, misalignment can occur.

    This is what I found:
    [YOUTUBE]http://www.youtube.com/watch?v=WqT_XfK2G-c[/YOUTUBE]

    I figure if I put a piece of thin, metal shim stock in there and tighten things up the way they should, I'll be able to line this baby right up! :cool:
     
  7. dances_w_clouds

    dances_w_clouds Subscriber

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    There is adjustable lens boards for the Beseler that may help the adjustment for your lens
     
  8. Vaughn

    Vaughn Subscriber

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    The bumper is used to make alignment adjustments (or at least I do on the 8 23C's that we have). A noticeable change occurs when I am using the laser alignment tool I have. But I will also be checking those screws when I align all of them before classes start in the Fall!

    Vaughn
     
  9. Worker 11811

    Worker 11811 Member

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    I wish I had the laser thingamajig! I've got to do it with a spirit level, some test film and my eyeballs. :wink:
     
  10. Vaughn

    Vaughn Subscriber

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    I just use the laser to get it as close as I can, then use a test negative (scratched in a test pattern) to do the final adjustment. It is the light that hits the baseboard that matters!
     
  11. Worker 11811

    Worker 11811 Member

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    I was able to get the difference between the top and the bottom of the image down to about half of what it used to be.

    I spent a lot of time fussing around with shims and putting them in all different places with varying amounts of success. Finally, I took off the thumbscrew that tightens the X-axis adjustment of the lens board and found that there were two thin washers sandwiched between the frame and the enlarger chassis.

    "Aha!" I thought. It looks like somebody designed the enlarger to be adjustable by changing the number of washers in there.
    I just happened to have a bunch of that exact kind of washer my toolbox, out in the garage. I got a few of them and was able to improve it. I only have to turn the knob by half of what I had to before in order to focus the top or the bottom.

    I'm getting tired and a bit frustrated. I'll look at it tomorrow or the next day when I can do it with a fresh mind.
    Cross my fingers... This might be fixed! :smile:
     
  12. Vaughn

    Vaughn Subscriber

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    I have used washers to adjust drooping lens platforms on the Omega D5's -- I hope that you have luck today!

    Vaughn
     
  13. Worker 11811

    Worker 11811 Member

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    I have the owners manual. It doesn't give much information on maintenance or alignment. I don't have a service manual. Is there such a thing? I'd like to get my hands on one if I could.

    ----------

    I have spent some more time working on this problem today. I have had varying degrees of success but have eventually ended up back where I started.

    I have ended up taking apart the whole lower half of the enlarger head. Everything below the film trap: Lower bellows, lens carriage focus rack, etc.

    First off, I have found lots of lovely places where dirt can hide. I'm going to have to attack that problem before going deeper into the question at hand.

    More importantly, I found that there was already a metal shim behind the pivot screw that holds the lens carriage in place. There is also a wave washer on that pivot. It looks like shimming and tightening is the way one is supposed to align this beast.

    What I'd really like to know is whether there is a published procedure for alignment of this mechanism and whether there is a jig or a guage that one can use to assist. (There are special jigs that are used to align movie projectors.)

    It looks like I'm going to end up taking most of the enlarger apart, clean and relube all the parts before reassembling and realigning everything.

    I don't mind doing the work. I just don't like working in the dark very much.
     
  14. Worker 11811

    Worker 11811 Member

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    Okay! I finally figured it out! It took me a day and a half to figure it out but, now that I see how it works, it should take the average person about 20 minutes to do the job with just a 6-inch spirit level and a piece of test film.

    The main way of adjusting the Y-axis focus is by turning the shoulder screw that acts as the pivot for the lens board.

    X-axis is adjusted by loosening the thumbscrew and rotating the lens board until you have it the way you want it. But, above that thumbscrew, there is a large shoulder screw that acts as the pivot. Carefully loosen or tighten that screw to affect Y-Axis focus. If you run out of room to make adjustment you might have to use shims behind the lens carrier. You can place one or two thin shims under the X-axis adjustment thumbscrew or you can place a thin shim behind the pivot screw.

    There is a wave washer on the head of the pivot screw. That is what led me to the discovery. If there was not a need to hold tension on the lens carrier there would not need to be a wave washer there. One could simply tighten that screw all the way down. (In fact, that's what I had been doing.)

    Further, I found that the vertical "bumper stop" screw does not affect image focus very much. It does affect whether the image is square from front to back but it has very little to do with focus at all.