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  1. #11

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    The late Canadian photographer Gene Nocon wrote a book about printing and focussing the lens on the baseboard. He explained that because B&W images are only really interested in the blue end of the spectrum the focussing should be made with a grain magnifier which has a blue filter. He has images in his book demonstrating the difference between a non-blue filter focusing image and one where a blue filter is used. It does apper quite dramatic. The focussing magnifyer is one that used to sold in UK under the Peak name but was available under different names.

    I happen to have one of these grain magnifiers but sadly no blue filter, so I use the colour gead on the LPL enlarger and dial in 50Y and 50C which gives a good blue light source. And yes I can support his theory that a blue filter does improve the focus point when using B&W. Obviously with colour neg there is no use for the blue filtration.

    I focus wide open using my Nikkor 2.8/50 and then stop down to f11 for normal negatives and F8 for those a little denser. Corner to corner sharpness guaranteed.

  2. #12
    darkosaric's Avatar
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    Wide open with grain focuser on maximum size, then wide open on some small size (like 15x20cm) with grain focuser to check if autofocus is ok (V35 focomat).

  3. #13
    baachitraka's Avatar
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    Perhaps, it is good to consider the focus with paper.
    OM-1n: Do I need to own a Leica?
    Rolleicord Va: Humble.
    Holga 120GFN: Amazingly simple yet it produces outstanding negatives to print.

  4. #14

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    Quote Originally Posted by BMbikerider View Post
    The late Canadian photographer Gene Nocon wrote a book about printing and focussing the lens on the baseboard. He explained that because B&W images are only really interested in the blue end of the spectrum the focussing should be made with a grain magnifier which has a blue filter. He has images in his book demonstrating the difference between a non-blue filter focusing image and one where a blue filter is used. It does apper quite dramatic. The focussing magnifyer is one that used to sold in UK under the Peak name but was available under different names.

    I happen to have one of these grain magnifiers but sadly no blue filter, so I use the colour gead on the LPL enlarger and dial in 50Y and 50C which gives a good blue light source. And yes I can support his theory that a blue filter does improve the focus point when using B&W. Obviously with colour neg there is no use for the blue filtration.
    Not buying that. It may depend on how crap one's enlarging lens it, but I've tested it with graded paper and found no difference. Furthermore, variable contrast paper is sensitive to blue and green. So I would advise against the blue filter thing.

  5. #15
    ic-racer's Avatar
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    How do you focus your enlarger? -- Just like I focus a view camera!

    Method for critical focus when negative is not held flat or lens is not perfectly flat field. Focus the enlarger by moving the head on the column and focus like a view camera. Focus on the corner of the image and note where the column is. Then focus on the center of the negative without touching the focus knob, by moving the enlarger head. Then set the head to the point exactly half-way between the extremes. This will optimize your depth of field at any aperture.

    If you want, you can actually calculate the aperture to get it all in focus based on the focus spread (based on view camera focus equation of Hansma).

    N = 20/(1+M) * square root of 'dv'

    N = Aperture number
    20 = user dependent constant (circle of confusion 0.15mm for me)
    M = magnification
    'dv' = millimeters of focal depth on the enlarger column.
    Last edited by ic-racer; 10-21-2013 at 02:42 PM. Click to view previous post history.

  6. #16

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    Quote Originally Posted by ic-racer View Post
    'dv' = millimeters of focal depth on the enlarger column.
    This puzzles me, care to explain.

  7. #17
    cliveh's Avatar
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    Quote Originally Posted by BMbikerider View Post
    The late Canadian photographer Gene Nocon wrote a book about printing and focussing the lens on the baseboard. He explained that because B&W images are only really interested in the blue end of the spectrum the focussing should be made with a grain magnifier which has a blue filter.
    What a load of tosh. Full aperture, no filtration, focus by eye the check with magnifier.

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

  8. #18
    Mainecoonmaniac's Avatar
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    I wonder if filtration is one of the factors in focusing since it changes the wavelength of the light?
    "Photography, like surfing, is an infinite process, a constantly evolving exploration of life."
    Aaron Chang

  9. #19

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    I posted a thread a few years back in which I tested this with different filters, moving the easel up/down etc. It was based on Ctein's focusing "gotcha" thing. I found no difference. Generally one focuses with white light or whatever filter is in place.

  10. #20

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    I focused my leitz focomat Ic once, using a grain magnifier.

    Since then, set it and forget it, as they say... (self-satisfied grin)

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