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  1. #11
    clayne's Avatar
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    Quote Originally Posted by Thomas Bertilsson View Post
    False alarm...

    I had to go from an aperture of f/8 to f/5.6 on the lens. That's enough to introduce un-sharpness... I did the same print at f/8 and things are fine again. Damned enlarger lens, it's supposed to be a good one, a Rodenstock Rodagon. The sharpness at f/5.6 compared to f/8, in a print as small as 10x10" is very poor. Clearly visible to the human eye.
    This sounds very suspect to me. Unsharp across the entire print @ f/5.6?

    There is no way the difference between 1-stop should be clearly visible to the human eye with a Rodagon, especially at 10x10" so I believe something else is amiss.
    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

  2. #12

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    Quote Originally Posted by clayne View Post
    This sounds very suspect to me. Unsharp across the
    entire print @ f/5.6?

    There is no way the difference between 1-stop should
    be clearly visible to the human eye with a Rodagon,
    especially at 10x10" so I believe something else
    is amiss.
    I wouldn't be so sure of that. A stop down with my
    F/5.6 El Nikkor is easily seen as sharper. Dan

  3. #13
    ath
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    Aligning the enlarger properly and using a glass carrier gave a major rise in technical quality of my prints.
    Suddenly all, even the "grainless" films printed with grain...
    Regards,
    Andreas

  4. #14
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    I would suggest to inkjet yourself a test grid onto transparency stock and put it in the enlarger to check the alignment, with the lens wide open. You can of course also check the registry with a grain finder but it is much more difficult and better for fine tuning.

    I also doubt that there will be significant differences between 5.6 and 8 except maybe in the extreme corners. But bear in mind that I don't enlarge much, the largest prints I make, even from 4x5, are typically 11x14 or smaller. If you are enlarging significantly beyond that then you may indeed need to stop down to f/11 or whatever. Anyway, as I am sure you are well aware, there is almost no meaningful penalty in resolution when stopping down to f/11 - f/22, and there may in fact be significant gains in corner res and overall smoothness of the illumination, so... it's your call. Nevertheless a registry check may be in order. (Now why do I have a strong feeling that somebody is going to lecture me on diffraction limited lp/mm through a stopped down enlarger lens...)

    Actually I never use a glass carrier. I never came to terms with the idea of something touching my negs
    "Only dead fish follow the stream"

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  5. #15
    Bob Carnie's Avatar
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    I have been using every size of enlarger lenses, rodenstock mainly.
    With a glass carrier, properly aligned, there is no shift in focus if you focus grain wide open then close down two stops.
    If someone here can prove that a shift is happening then I say their lens is crap and align their enlarger and use glass.
    After a few hundred thousand focuses over the last thirty five years I have never once seen this shift when aligned and using glass.
    Ok maybe I bumped into the enlarger once or twice, maybe I swatted the head while changing filters, maybe I hit the easel or kicked the feet, maybe a train went by and bumped the room I was working in.
    But we are talking about good lens , glass and aligned , focus shift is not going to happen.

  6. #16
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    Every lens MTF or resolution test for enlarger lenses I can recall ever seeing shows more sharpness at the center at f5.6 vs f8.

  7. #17
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    Quote Originally Posted by ic-racer View Post
    Every lens MTF or resolution test for enlarger lenses I can recall ever seeing shows more sharpness at the center at f5.6 vs f8.
    Yes but that's only part of the story. We just had a very annoying thread on this very topic. Bottom line (for me at least) is that it's not only about center sharpness. Please visit this flashlet and play with the aperture dial. You will see evidence for what you describe as well as some other very important things going on off center.

    While this particular demo is not for an enlarger lens, the behavior is quite typical and evidenced in almost any chart on any lens.
    "Only dead fish follow the stream"

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  8. #18
    Bob Carnie's Avatar
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    I have sold to discerning photographer thousands of prints, to my eye and theirs the prints are sharp.
    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.

    Every technician I have ever worked with focus lens wide open and decide on whether to stop down or not, I stop down two stops from wide open using apo glass,and have never seen a difference.

    Maybe I am missing something here, and have been doing it all wrong all these years... I hope my clients don't find this out.

  9. #19
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    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.
    f/22 and be there.

  10. #20
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    I've always refocused at the aperture I'm going to print at. It can make a difference. After printing all day I find spotting relaxing so you can send me your prints to spot.

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