Home Made Alignment Tool

Discussion in 'Enlarging' started by dr bob, Jan 1, 2005.

  1. dr bob

    dr bob Member

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  2. Mongo

    Mongo Member

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    I have to wonder why he went through the trouble of drilling through the mirror for the LEDs...wouldn't this have worked just fine with the LEDs, the wires, and the batteries all on the mirror surface? Also, rather than drilling a hole in the mirror for viewing, why not just scrape away the silvering from the center of the mirror and leave the glass in place?

    Don't get me wrong...his solution is great...it just seems a bit over-engineered to me.

    And as long as I'm picking nits....a mirror placed at a 45 degree angle to the hole would work as well as the pentaprism...just that the image wouldn't be upright so you'd have to mentally rotate it when you make the alignment changes to the enlarger.
     
  3. Neal

    Neal Subscriber

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    Dear Mongo,

    I must agree with you, he has a great solution.

    If I had to guess, drilling a few holes is easier than building a frame to keep the diodes straight and it is easier to use a pentaprism than install a mirror at exactly 45° without a machine shop.

    Now, how can the mirror be attached to the lens to align that?

    Neal Wydra
     
  4. Loose Gravel

    Loose Gravel Member

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    Use mirrored plexiglass. It makes drilling the holes a whole lot easier.
     
  5. paul ron

    paul ron Member

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    Mirrored plastic is not optically flat, the variations in the surface will not allow you to get proper parallelism<sp?> of the planes.
     
  6. lee

    lee Member

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    I have a set of mirrors that are front surface and instead of drilling a hole we just scratched some of the silver off so we could see through it. We used these mirrors to optically alighn the copy boards with the film plane


    lee\c
     
  7. Loose Gravel

    Loose Gravel Member

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    No, plexiglass is not optically flat. Optically flat is defined in fractions of a wavelength of light. I don't think anything in my darkroom is that flat and mirror tile is not optically flat either. Cast plexiglass has worked for years. It is 0.005"/ft flat. Probably as flat as mirror tile, negatives, lensboards, lensboard alignment, the edges of your enlarging paper, image flatness, negative holders, and the rest, all RSS'd together. This is photography, not laser interferometry.
     
  8. dancqu

    dancqu Member

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    When all is said and done the trapezoidal method should
    provide the most perfect alignment possible. I do not believe
    the method can be faulted.

    Not much is heard of the trapezoidal method probably
    because it does not sell any equipment. Dan
     
  9. pwcphoto

    pwcphoto Member

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    Seems like a lot of work

    Seems like a lot of work, I don't want to think about how many mirrors were cracked in the process, that is a lot of bad luck at 7 years a crack! ;=] Pretty neat concept though.

    I purchased a laser aligner at a trade show many years ago. It produces a laser beam that is perpendicular to the paper plane (easel) or baseboard. They supply a front surface mirror that sets in your negative carrier and one that fits in the lens board.

    Basically you shine the laser up with the lens removed and adjust the negative carrier so that the beam falls back down on the emiiter, if you see it anywhere else you are out of alignment. The higher the enlarger head the greater the accuracy as the error is magnified. You do the same thing for the lens board and you have a nicely algined enlarger with all planes parallel. It is very fast.


    I have a pair of Suanders LPL-4550XLG enlargers and I must say that out of the box, they are about the most accurate I have ever seen, almost no adjustment required. Can't say that for my Zone VI or Omega's.

    Phil
     
  10. dancqu

    dancqu Member

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    That very narrow beam of light is almost as small as one
    of the infinite number of points which make up a plane.

    The trapezoidal method is a more real world method as
    it uses the carrier or a negative in the carrier and it's
    projected image to make the alignment.

    In a nut shell, a square in the carrier must project a
    square and it be in focus across the entire plane.

    Actually I think trapezoidal to be a misnomer. Dan
     
  11. L Gebhardt

    L Gebhardt Subscriber

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    Dan, with the laser you can move it around the baseboard to check that everything is aligned. I have never seen a difference as I have shifted it around. Remember, it you are perpendicular to one point on a plane you are perpendicular to all points on the plane.
     
  12. dancqu

    dancqu Member

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    " ... if you are perpendicular ... " A first BIG IF in my book.
    I suppose it is assumed the ray is projected perpendicularly
    within some degree of manufactureing tolerance; the base
    of the tool, the insetting of the emitter, quality control
    allowances, etc.

    Using the trapezoidal method all I need are a square, ruler,
    and hand tools. The proof of good alignment is a square all
    corners image, sharp across the entirety of it's plane. Dan