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Thread: Are all grain focusing tools created equal?

  1. #21
    Jac@stafford.net's Avatar
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    Re: Are all grain focusing tools created equal?

    Quote Originally Posted by Ted R View Post
    It is made to focus on an image at the same distance as the plane of the base, this is fixed by design. What IS adjustable is the eyepiece focusing, both the Patersons and the PEAK (and MICROMEGA) include adjustable eye focus for the target.
    Yes, by the easel's base - with a sacrificial piece of printing paper on the easel. The Peak/Micromega eyepiece focuses, and also swivels vertically.

    Corran, once you use the focuser it won't matter how it works. It just works. Focus upon the grain and be happy. An interesting application is to get the grain in focus, then stop down the lens to watch for focus shift (should not happen), and see when the grains mushes out due to diffraction.

  2. #22
    Corran's Avatar
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    Re: Are all grain focusing tools created equal?

    Fair enough - if I don't have to worry about it, that's fine. I noticed that when moving the focus on the eyepiece the aerial image defocused...and then I could "refocus" the image. Hence my question.

    I will leave it at it's default setting. Seems to work fine anyway (prints are sharp enough).
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  3. #23

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    Re: Are all grain focusing tools created equal?

    Quote Originally Posted by Corran View Post
    What is the generally accepted way of ensuring the grain focuser is focusing on the right point in space? This has been nagging me for a while during print sessions.
    There is a mark of some sort in the viewfinder. On my Micromega, it is two, pale gray, concentric circles. You adjust the eye piece (diopter) until the mark(s) is as sharp as it can be -- with or without glasses. Just make sure when you use it, you use it the same way -- with or without glasses. Micromega, and I assume Peak, made long-mirror, grain focusers -- with and without the tilting eyepiece. The one with the tilt runs about twice as much. I have the model without the tilt and have no complaints -- it reads WAY off-center if I want.

  4. #24
    Corran's Avatar
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    Re: Are all grain focusing tools created equal?

    Thanks, I feel dumb. The two concentric circles in the center of the field I never even thought about. Now I know.
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  5. #25

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    Re: Are all grain focusing tools created equal?

    Quote Originally Posted by Corran View Post
    Thanks, I feel dumb. The two concentric circles in the center of the field I never even thought about. Now I know.
    Lord T'und'rin Jaysus laddie, don't you dare say you feel dumb !!
    You're a model for us all to follow...
    None of us reads this forum, but to learn !

    And, watching your posts and pictures, we've all learned from you.

  6. #26
    Corran's Avatar
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    Re: Are all grain focusing tools created equal?

    Lol! Thanks. Always more to learn!
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  7. #27

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    Re: Are all grain focusing tools created equal?

    Men are born ignorant, not stupid. They are made stupid by education. ~ Bertrand Russell

  8. #28

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    Re: Are all grain focusing tools created equal?

    Quote Originally Posted by Jac@stafford.net View Post
    Yes, by the easel's base - with a sacrificial piece of printing paper on the easel.
    In tests I was unable to demonstrate loss of sharpness due to paper thickness effect. Some calculations made about a year ago for depth of field at the negative stage strongly suggest depth of focus at the paper easel is by comparison much larger and much greater than the thickness of a piece of paper. This allows the easel to be tilted for perspective adjustment without significant loss of sharpness.

  9. #29

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    Re: Are all grain focusing tools created equal?

    Quote Originally Posted by Ted R View Post
    In tests I was unable to demonstrate loss of sharpness due to paper thickness effect. Some calculations made about a year ago for depth of field at the negative stage strongly suggest depth of focus at the paper easel is by comparison much larger and much greater than the thickness of a piece of paper. This allows the easel to be tilted for perspective adjustment without significant loss of sharpness.
    Depth of field is the area in front of the lens. Depth of focus is behind the lens.

  10. #30

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    Re: Are all grain focusing tools created equal?

    Thank you, however I beg to differ, my understanding is that the illuminated negative is the object, located in front of the lens, and the projection onto the paper is the image, located behind the lens. Thus depth of focus applies to the projected image.

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