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  1. #1

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    Grain Focusing - discrepancies

    Hello,

    I've got a problem. I was curious about my grain focuser - a Micro Sight II. I compared it to a Micromega Critical Focuser (the high end Peak ones). The two focusers were different. That was disconcerting. So I grabbed another Micromega Criticla Focuser, and a Peak Enlarging Focuser II. Guess what. All slightly different.

    Truthfully, I don't really know how these things work. They're one of the few pieces of equipment in the darkroom I trust blindly. For them to all give differing information; well that is no good.

    To preface: I use a glass carrier in a Durst 138s. I keep my enlarger aligned with a versalab alignment tool. I'm confident all is good on that end of things.

    So here's what I did. I have one of those "test pattern" focusing negs. The one in question is made by Jobo. I loaded it into the carrier, and made a 5x7 crop from a relatively big enlargment (12x16 ish). I marked each of the four grain focusers, and made RC prints from each focusing as sharply as I could on the same spot on the neg. I also made one print where I focused by eyeballing it. I made the exposures with the lens wide open, hoping to take depth of field out of the equation as best as I could. I batch processed the prints and dried them.

    I went through the 5 prints, and ranked them in order of sharpness. I gave them to my girlfriend, and she did the same.

    The results? The eyeballed print was - by some margin - the sharpest. We both came to that conclusion.

    This has me dumbstruck. What is the point of the grain focuser if the information it provides is not reliable? Those Micromega Critical Focuser are supposed to be high end tools. They sell for a small fortune.

    The problem is, while it's easy to eyeball and focus these "test pattern" negs, it's not so easy to do the same with an overexposed shot from a Holga lets say.

    I'd love your thoughts on this. Is the "test" valid? How can I remedy the situation?

    Thanks!

  2. #2

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    Who cares if an over exposed holga shot is critically sharp?
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  3. #3
    Newt_on_Swings's Avatar
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    Grain Focusing - discrepancies

    Did you happen to follow the manufacturer's instructions on setting the focus of those grain finders/focusers? Also did you place a sheet of paper under the finders the same thickness of the paper you are printing with? Another issue can also be vibration after focusing.

    I have used a number of finders in the past, my favorites are the 25x microsight and my peak 1 focuser. I have also used the hocus focus sometimes which works fairly well with such a simple design. The larger peak helps with viewing corners. It also has a blue filter which has been debated about its effectiveness.

  4. #4

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    Did you calibrate your grain focuser? If you look into a grain focuser, you will see a hair either going across or in X shape. You should also be able to twist your eye piece. You are supposed to turn your eye piece until the hair is critically in focus. Then you could use your focuser to focus on the projected grain.

    I have seen focusers with this hair missing. There's no way to calibrate that....
    Develop, stop, fix.... wait.... where's my film?

  5. #5

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    Unless you expose prints with the lens wide open you should not have a problem. Once stopped down the depth of field should make any small inconsistencies meaningless.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  6. #6
    ic-racer's Avatar
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    I'll gladly take all the bad ones.

  7. #7

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    If you don't adjust the eyepiece on the grain focuser to match your eye, do it with the image WAY out of focus, then the focus on the print should be almost perfect. Otherwise it could be way way off, especially if you are young and have eyes that will adaptively focus too easily.
    Bob

  8. #8
    Steve Smith's Avatar
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    Quote Originally Posted by Newt_on_Swings View Post
    Also did you place a sheet of paper under the finders the same thickness of the paper you are printing with?
    We busted that myth a couple of years ago. I contacted some manufacturers of grain focusers and the conclusive view was that it doesn't make any difference.

    The depth of focus at the paper is quite large whereas the position of the negative is very critical. You cannot move the negative with respect to the lens with enough precision to make any difference as small as the thickness of paper.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  9. #9

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    Eyeball focusing will get tougher and tougher as we grow older, especially after spending longer time in DR under the safe light. As long as the same unit can yield the consistent results, it should be OK. Of course, sometime it could be a little frustrating when grains are too fine.

  10. #10

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    So, to answer some questions: Yes, I did calibrate the grain focusers to my eyesight. The Micro Sight and Micromega Critical focusers make it relatively easy to do. So that's taken care of.

    I didn't use a piece of paper under the focuser. But that was consistent. I didn't put paper under *any* of the focusers. It doesn't explain why the results from the four instruments would differ.

    For Gerald Koch: You say that if I stop down, there shouldn't be a problem. I respect that, but it still bothers me. Surely the grain is either in focus or it isn't. I do have a couple of negatives that I have to print wide open, particularly if I'm doing a large enlargement. When I'm lith printing, I routinely print wide open.

    Is there any way to calibrate a grain focuser other than by adjusting it for your eyesight? I suppose there really isn't.

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