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  1. #21

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    Quote Originally Posted by BetterSense View Post
    I often print at f/22 if it results in reasonable print times.
    I haven't noticed it unsharpening my prints. Perhaps
    I should do more testing.
    Smaller apertures work to correct lens aberrations.
    Some that may be affected include Astigmatism,
    coma, spherical, chromatic, and a few others;
    depending upon the lens.

    Likely diffraction limiting takes a visable toll only at
    very small apertures; perhaps beyond f45. A mute
    point when enlarging due to prolonged exposures.
    Also, diffraction is a function of the absolute size
    of the aperture. For example, two lenses at the
    same aperture will exhibit diffraction in
    proportion to their focal length. Dan

  2. #22
    Guillaume Zuili's Avatar
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    Let me tell you something about Bob...
    This gentleman has a nasty habit to cut my 35mm strip into single frame to put it into his glass carrier...
    I hate that.
    But... Bob made 30x40 prints which were tack sharp.
    I had this issue before. Very frustrating after a long lith dev to see the final image with one corner out of focus.
    Now I only use glass.
    You should do so Thomas.
    If you go close to Bob one day just look for his scissors and hide them !
    Just to piss him off.
    Otherwise you can trust him 100%.
    :-)

  3. #23

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    Correction

    Quote Originally Posted by dancqu View Post
    Smaller apertures work to correct lens aberrations.
    Some that may be affected include Astigmatism,
    coma, spherical, chromatic, and a few others;
    depending upon the lens.

    Likely diffraction limiting takes a visable toll only at
    very small apertures; perhaps beyond f45. A mute
    point when enlarging due to prolonged exposures.
    Also, diffraction is a function of the absolute size
    of the aperture. For example, two lenses at the
    same aperture will exhibit diffraction in
    proportion to their focal length. Dan
    The last sentence should read: ... will exhibit
    diffraction inversely in proportion to their focal
    length. Dan

  4. #24
    smieglitz's Avatar
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    Well. I'm glad this thread just turned out to be something simple about lenses and negative carriers. When I read the title, I thought Thomas was off again combining split-grade filter printing with unsharp masking on lith prints on Solstice dates or some such thing.

  5. #25
    Guillaume Zuili's Avatar
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    :-) :-) :-)

  6. #26
    Kvistgaard's Avatar
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    Quote Originally Posted by Bob Carnie View Post
    Thomas is posting on a problem that I think is caused by not using a glass carrier. Second exposure or during the first I suspect the neg is popping.
    Bob - excuse my ignorance, but when you refer to glass carriers- is that one or two layers of glass (the latter with the negative sandwiched in between the glass)?

    Currently I am using just one layer of glass (above the neg), for both 120 and 135, and results are reasonably sharp. This is advice I picked up from one of Barry Thornton's books, along with the instruction to stop down your lens before adjusting focus (using a grain finder).
    S°ren

    "We are much more likely to act our way into a new way of thinking than think our way into a new way of acting." - R. Pascale

  7. #27
    Guillaume Zuili's Avatar
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    He refers to 2 layers of glass.

  8. #28
    Bob Carnie's Avatar
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    Yes I am referring to two layers of glass, antinewton on top regular on bottom.
    I sometimes do use only a single layer of anti newton on to and none on the bottom, but I am printing murals with very long exposures and quite a few filter changes . I want make sure that the negative has no chance to move as a 30x40 sheet of paper is expensive and removing any problem areas is critical to me.

    Bob
    Quote Originally Posted by Kvistgaard View Post
    Bob - excuse my ignorance, but when you refer to glass carriers- is that one or two layers of glass (the latter with the negative sandwiched in between the glass)?

    Currently I am using just one layer of glass (above the neg), for both 120 and 135, and results are reasonably sharp. This is advice I picked up from one of Barry Thornton's books, along with the instruction to stop down your lens before adjusting focus (using a grain finder).

  9. #29
    clayne's Avatar
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    Quote Originally Posted by Bob Carnie View Post
    Yes I am referring to two layers of glass, antinewton on top regular on bottom.
    I sometimes do use only a single layer of anti newton on to and none on the bottom, but I am printing murals with very long exposures and quite a few filter changes . I want make sure that the negative has no chance to move as a 30x40 sheet of paper is expensive and removing any problem areas is critical to me.

    Bob
    Bob, on a side note, what's a typical exposure time for a 30x40?
    Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.

    http://www.flickr.com/kediwah

  10. #30
    richard ide's Avatar
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    One thing I tried which seems to work well is mounting the negative base side to the glass with mineral spirits. You just need the top glass.
    Richard

    Why are there no speaker jacks on a stereo camera?

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