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  1. #1
    JeffD's Avatar
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    grain focuser questions

    I am new to enlarging 4x5. I have a grain focuser left over from my 35mm enlarging days which seemed to work fine way back when.

    I now have a 4x5 enlarger, and, when projecting a 16x20 image, in no way can I check the edges or corners- the view in the scope goes from a small "ufo" saucer shaped image, to no image at all at the edges.

    I guess my old cheap grain focuser is not good for this.

    I am now using a 135mm lens.

    Is this the fault of my focuser, my lens, or what?

    Is there a feature in a grain focuser I should look for to be able to check the edges of my print?

  2. #2

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    Quote Originally Posted by JeffD
    Is there a feature in a grain focuser I should look for to be able to check the edges of my print?
    Most grain focusers are made to be used only in the center of the print. I know only the different models of the Peak enlarger that are useable in the edges, notably the Peak #1 (usable 30 deg. off axis)

    Martin

  3. #3
    edz
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    Quote Originally Posted by JeffD
    I guess my old cheap grain focuser is not good for this.
    Correct.
    I am now using a 135mm lens.
    Does not matter.
    Is this the fault of my focuser, my lens, or what?
    Its not a fault but (a shortcomming of) the design of your grain focuser. The only grain focuser to my knowledge that allows for view outside of the center is the Z. Koana concept focusers with rotating ocular sold as the Peak#1 (2000) or Micromega. If your enlarger, however, is properly aligned then the center focus should be quite sufficient-- if not most appropriate--- to the task. In a properly designed system, afterall, if the negative is correctly focused in the center then it'll be focused as best as can be at the edges---and, if not, there's hardly much one can do beyond trying to align things and maybe turning the aperature down. I view the Peak more as a diagnostic, aligment and test instrument than as a grain focuser. In focusing I see sometimes advantages to using my (historical) Tourret Scoponet due to his higher form or one of my mirror boxes.
    Edward C. Zimmermann
    BSn R&D // http://www.nonmonotonic.net

  4. #4

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    Not a consideration for me

    I use a Scoponet. It is not any good when used very far off axis. I enlarge with glass carriers on an enlarger that stays in alignment. I use an enlarging lens whose field is adequately flat...for 35mm I use a 63mm 2.8 EL Nikkor N. It is an exceeding satisfactory lens. Because of this I do not find the lack of ability to view the edges or corners of the field to be any short coming whatsoever. When the negative is put into the carrier I use a light table and check the negative for sharpness and for dust with a 7 power loupe.

    There are, however, a few cautions to be observed in using magnification in focussing the enlarger.

    Firstly there are two types of devices for doing so. I). A ground glass device that functions similar to looking at a focussing screen on a camera.
    Generally a dimmer image and lesser magnification is used with this type of device.

    Secondly, an Aerial image magnifyer that is used to judge an aerial image of the projected negative. Generally, thes devices use more magnification than the ground glass variety. One must use care to not focus using this type of device with filters in the light path. Your results can be compromised by the nature of human visual response. Patrick Gainer, in Photo Techniques magazine wrote a very worthy article about this. He is to be commended.

    Either type of device is capable of being a very large improvement in achieving proper focus with an enlarger.

  5. #5
    JeffD's Avatar
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    Thanks! I was given an old Beseler 4x5 enlarger, and I did my best to adjust it to where the negative carrier plane, lens plane, and baseboard are parallel.

    I guess I was hoping for a verification that I did this correctly by seeing nice grain, when focused, all across the image, when projected moderately large (16x20).

    Looks like most grain focusers won't do this.

    I suppose I could get some kind of 4x5 test negative, with a fine test pattern across it, and print it, to see if I get much "fuzziness" near the edges.

  6. #6

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    misaligment

    Misalignment will not take the form of having soft or out of focus edges. It will take the form of one side of the print being sharp when another side is visibly less sharp but that you know is sharp all over. Even if you are not going to use glass carriers, putting a negative between glass will at least get negative buckling removed from your evaluation. Care is required in determining if the misalignment is due to the enlarger or if it is due to a lens with misaligned element(s). Ctein's book Post Exposure will tell you how to test for both. I believe that any top qualty enlarging lens made for 4x5 use should have an optimum aperture of no more than 1 stop down from wide open.

  7. #7
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    There are times when a substitute target is useful. A cleared piece of film with a scratch or two on the emulsion side is easily focused. It is more useful when you are using a glass carrier. You can scribe a line with a razor blade or Xacto knife.

    I wrote that article for Photo Techniques because there was a lot of discussion about errors of focusing due to supposed inadequate correction of lenses for blue and near UV light. Astronomers have known for years that the chromatic aberration of the eye makes the telescope objective look bad. What I found in my experiments is that there are two effects of chromativ aberration of the eye. One is due to the fact that the resolving power of the eye is best with green or white light. As a consequence, the spread of focusing errors is greater as the light is either bluer or redder than the color of best resolution. This being the case, one would expect and indeed finds that there is a bias away from the point of best focus when the focusing light is not green or white. You can demonstrate what causes this bias by viewing a printed page through deep red and deep blue filters in succession, bringing the material each time to the position of closest clear vision. You may be surprised at the difference in position of clearest focus.
    Gadget Gainer

  8. #8
    Bob Carnie's Avatar
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    Jeff
    When I want to see if my set up is ok on any 4x5 enlarger I do the following.
    1. use glass carrier
    2. 35 mm negative
    3. 12x18 image size
    4. make a print, focus on the center
    5. If the grain is sharp in the middle , middle top/bottom, edges middle/top/bottom, then you know your enlarger is aligned. If you do not see grain in these 9 points then leveling the negstage and film stage to baseboard is due.
    There is lots of past threads on this issue , where you can get some good tips.
    I have peak and other cheaper grainscopes and I always focus on the middle area . try to find a contrast difference area for best results.

  9. #9

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    Quote Originally Posted by Claire Senft
    ... using magnification in focussing the enlarger.
    Firstly there are two types of devices for doing so.
    Four. I find correct focus is best determind using both eyes
    wide open. For that I use high diopter reading glasses.

    A fourth device is a two to four power magnifying glass. Lets
    be resonable. With either of the two devices I've mentioned
    one is very closely and at some magnification seeing a full
    sized projected image.

    I've a grain magnifier and think it good for checking grain. Dan

  10. #10
    Terry Hayden's Avatar
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    plane of focus

    My .02 -

    Since we use large negatives here at work ( 9x9 ) and make fairly large
    enlargements ( up to 40 x 50) a an observation may be in order:

    We have not found any ( componon-s, el nikkor, etc) enlarger lenses that project on a truly flat plane. In other words, when the center is in focus, the edges are not as sharp.

    Generally we have found a "dome" of sharp focus. When the edges are sharp, the center point of sharp focus is above the easel.

    This is true when all four edges are sharp. It's not an alignment issue since we use a restitutional enlarger that allows for tip and tilt of the lens stage to maintain proper scheimpflug (sp?) orientation.

    The negatives are in a glass carrier so it's also not a flatness issue.

    Of course stopping down takes mostly takes care of it. Out of habit now, we get the edges sharp, then refocus off center ( the old adage of a 1/3 in front of the plane of focus and 2/3 behind for depth of field).

    Just a bit of info from experience.

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