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  1. #21
    Mick Fagan's Avatar
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    Dan, that is a point I had not considered, makes good sense. I will borrow a friend's Apo enlarging lens and see how that goes.

    I have been producing exceptionally sharp colour RA4 and EP2 prints from negatives, for around 20 years with this lens.

    I was of the understanding that this lens was, or should be alright for B&W. It could be though, that it has limitations with the latest VC papers.

    I have produced quite stunning pictures over 15 years ago with this same lens, but that was single B&W graded paper.

    I am learning a lot from this thread, makes life interesting, eh?

    Mick.

  2. #22

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    Quote Originally Posted by Mick Fagan View Post
    Dan, that is a point I had not considered, makes good sense.
    I will borrow a friend's Apo enlarging lens and see how that goes.

    I have been producing exceptionally sharp colour RA4 and EP2
    prints from negatives, for around 20 years with this lens.

    I was of the understanding that this lens was, or should be
    alright for B&W. It could be though, that it has limitations
    with the latest VC papers.

    I have produced quite stunning pictures over 15 years ago
    with this same lens, but that was single B&W graded paper.

    I am learning a lot from this thread, makes life interesting, eh?

    Mick.
    I've been looking for that article by Ctein. I recall it being
    in an issue of Photo Techniques. Very thorough. I gave it
    a couple of good readings but that was years ago.

    He analysis the problem light source to paper spectral
    sensitivity, condenser and dichro. IIRC, he does suggest
    the use of a UV type filter in the light path. At least B&W
    papers have an extended, exaggerated, blue-violet-UV
    sensitivity. Similar to films.

    Personally, I consider the BG filter a useful tool. Ctein
    tested it as well as other deep blue filters. He measured
    differences in focus by shimming the easel. I think it must
    have been one of his most laborious under takings.
    I'll keep looking. Anybody know which issue? Dan

  3. #23

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    In Ctein's later writing on the subject he conceded that a part of his focus error was due to this filter..approx. 4-5 mm at the easel if I remember correctly.
    Claire (Ms Anne Thrope is in the darkroom)

  4. #24

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    Quote Originally Posted by Claire Senft View Post
    In Ctein's later writing on the subject he conceded that
    a part of his focus error was due to this filter..approx.
    4-5 mm at the easel if I remember correctly.
    I've no context within which to place that remark.
    Mick has made it plain that there is much improved
    focus when he uses the deep blue BG filter.

    Perhaps focus error was the norm with whatever filter
    Ctein used. There is a spread of spectral wave lengths
    to which papers are sensitive. There is a band width to
    the filters used. Focus can be off some due to a
    paper's very short wave length response.

    Ilford's Oriental paper has a band width sensitivity of
    350 to 500 nano-meters and is most sensitive from 400
    to 450 nano-meters. IIRC the BG is most transmissive at
    470 nano-meters. Papers vary in their spectral response.
    Light sources vary.

    Ctein's article is rather involved and very exhaustive.
    The testing included a number of variables. I'm still
    looking for my copy of his article as I've a suspect
    105mm Nikkor which should be tested. Dan

  5. #25
    Matthew Gorringe's Avatar
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    That's a nice score Mick,
    the Sydney market was pretty bare 2 weeks ago. I was looking for one of these there but found very little of interest. I was offered a multigrade 500 head with all extras for $150 but apart from that there was almost nothing really. If you find another one of these (the model 1) don't hesitate to buy it and I'll forward you the money.

    Are Bromide/Chloro-bromide graded papers more finely attuned to the blue wavelengths and would the filter possibly work better with graded papers?

    Regards, Matt.

  6. #26

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    B/G filter..

    Mick - to answer your earlier question : The filter I used was cut from a Rosco swatch book : "daylight" Tough TD25 "Converts 3200K to 6000 K ".
    Hardly scientific ,in fact I'm of a mind to experiment with a variety of blue filters.
    I'll post my impressions.
    FWIW : all my lenses are EL Nikkors : 63mm/80mm/105mm/150mm , which are,according to Nikon "corrected for the near ultraviolet range,to which most black & white enlarging papers are sensitive".

  7. #27
    MattKing's Avatar
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    I wonder, what would the effect be of focussing with full cyan filtration dialled in on my dichroic head?

    or,

    What would the effect be of focussing with full cyan and full magenta filtration dialled in on my dichroic head?

    Matt

  8. #28

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    Quote Originally Posted by Smudger View Post
    ..."daylight" Tough TD25 "Converts 3200K to 6000 K ".
    I'm of a mind to experiment with a variety of blue filters.

    EL Nikkors : 63mm/80mm/105mm/150mm , which are,
    according to Nikon "corrected for the near ultraviolet
    range,to which most black & white enlarging
    papers are sensitive".
    Blue filters for viewing?
    I've a 105mm Nikkor to check. I'd take
    that Nikon quote to mean that the Nikkors are
    corrected THROUGH the near ultraviolet. If those
    very short and not so short wave lengths do coverage
    with all those longer wave lengths of the visible spectrum,
    then the BG or other deep blue will make no improvement
    in the focus. Dan

  9. #29

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    I've bought a Peak scope, but without any blue filter that I could see. I only read now after the fact about the blue filter.

    I'm wondering (without yet having a darkroom session to try it) if I could just put a normal camera lens Blue filter (Nikon B12 or B+W KB12, both of which I happen to have in my drawer here) over the Peak scope eyepiece to get the same effect when focusing a black & white neg????

  10. #30
    ic-racer's Avatar
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    I just got a second Peak 1 new in box, but it did not come with the plastic eyepiece lens cap. However, I found a good use for the included blue fiter---it acts as a good lencap for the eyepiece

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