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  1. #11
    Mick Fagan's Avatar
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    Yes, he had an article in Photo techniques, in January February 1997 which I have, and read when it came out.

    I carefully tested my own filter and had others test the same filter equipped peak focuser, using my enlarger.

    The enlarger is where I believe most problems come from, that is, most enlargers are not capable of exact fine focusing and locking of the negative stage.

    I have a DeVere 504 free standing enlarger, I know what enlarger was used in the published article.

    I have used a near identical enlarger as the one used in the testing for that article, I would agree with the results of the published article.

    I have also read carefully Ralf Lambrecht and Chris Woodhouse's book, "Way Beyond Monochrome". In their book Ralf and Chris have one chapter called, "Sharpness in the Darkroom". This is an excellent chapter as it contains a multitude of tips, one of the sections in that chapter has a section called, "Accurate Focusing", there is a sub heading about "Focusing with Filtered Light", it is in this section that they make reference to using a blue coloured filter.

    Their conclusion is the same as Patrick Gainer, it really doesn't work the best, mainly because a constant exact focus, is hampered by the human eye and it's poor light gathering capability in that part of the spectrum.

    Basically I agree with both of them, however, and one does have to have the however. I do believe that there is a difference and various people (four to be exact) using my darkroom and my enlarger, have agreed that there is a difference, it is noticeably better, but it is dependent upon having equipment and lighting capable of harnessing this quite accurate focusing ability.

    I have used some pretty interesting enlargers over the years, only a handful of these would be capable of utilising the power of very accurate negative stage movements with repeatable accuracy.

    The top end Durst units, which includes most of the 8x10" models, but none of the 4x5 models I have used. All of the vertical tabletop and free standing DeVere 504, 507 and 810 enlargers manufactured in the last 35 odd years that are equipped with the front focusing wheels and locking knobs alongside the vertical column.

    These are the only enlargers I have used, that would in my opinion, be capable of using a blue filter over a focusing lens, to obtain finer grain focusing.

    Any other enlarger I have used, and certainly most I have seen pictures of, are just not manufactured to the exacting standards of what I call a very precise machine, for that kind of focusing precision.

    I have spoken at length with my sister in-law's husband, he is an Opthalmic surgeon in Germany. He tested my filter and the wavelength of light that my blue filter passes, does present some difficulty with the human eye. Interestingly, the wavelength of my filter does correspond to that part of the spectrum the paper is subjected to (generally).

    There is an interesting aside to this, which I have since tested in my darkroom, grades of paper contrast. I would humbly suggest that as you deviate from about Grade 3 and get closer to either Grade 1, or Grade 5, the accuracy of the blue filter seems to be ever so slightly off. It is this possibility I am now testing.

    This is obviously an interesting subject, with many variables to consider.

    Mick.

  2. #12

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    That is really very interesting Mick. Thank you for posting that.
    Claire (Ms Anne Thrope is in the darkroom)

  3. #13
    jeroldharter's Avatar
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    Thank you all for the advice.

    I dug out the odd sized 55mm Heliopan 8x ND filter that woould fit my Schneider 150 mm Apo-Componon enlarging lens. That worked very well. Also, as someone pointed out, the ND filter let me open up the lens 3 stops to avoid diffraction.

    Then I tried to make a 16x20 of the same image. I use a Jobo Colorline 5000 analyzer in the integrated sensitometer mode to zero in on the appropriate exposure when I change enlargement ratios. That works pretty well, although the larger size still requires tweaks. Anyway, at the larger aperture of f5.6-8 that I was using, the image was horribly out of focus due to alignment issues. I unburied the Beseler alignment tool and made some minor tweaks but found no glaring alignment issues. I discovered that the issue is the lensboard for the Schneider lens. It is a big lens and requires a special lensboard (although it will fit on a standard board awkwardly). The special lens board does not have the two screws to lock down the board so it has a slight wobble which accounted for my sharpness problems. I swapped out the lens for a Rodagon 150 mm that I obtained "for free" as part of an Ebay indulgence and screwed down the standard lens board. I had never used or tested the Rodagon lens before. It is much smaller than the Schneider but my alignment issues were solved and the quality of the print was excellent with this lens.

    I think I will continue to use the Rodagon for this project until I have time to re-mount the Schneider and compare the two side to side for a large print. I also have a Nikkor 135 mm that I might include in the test.

    I know everyone talks about alignment being so important so I am careful about it. This is the first time I have had a problem but having seen the results I think alignment is perhaps the most important variable for getting sharp enlargements. I am not sure that I could discern any issues with diffraction though, so for this round of chaos at least, I think that alignment is a much more important issue than diffraction.
    Jerold Harter MD

  4. #14

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    Jerold,

    glad you fixed it, the only other option I can think of is a "Magnasight", a image focuser not grain focuser. Very handy that most people can wear their glasses and still use it also.

  5. #15

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    In ancient times (when I was in school), I learned to us a green filter when looking at the grain of metal samples through the microscope. It took a lot of getting used to, but eventually I realized it helped. Something like that may apply here as well. For enlarging, I actually avoid my grain focusing tool. I never could get used to it. Instead, I use an ordinary magnifying focus tool. My favorite is the MagnaSight, but I have an old Durst model as well. Once I learned to look really hard, I discovered that I could see and focus on the grain with these, even doing an 8X10 from 120. Incidentally, I'm nearsighted, and age has taken its tool on accommodation, but if I take off my glasses it works fine.

  6. #16

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    Quote Originally Posted by Doremus Scudder View Post
    Stopping down a lot for small prints because of the brightness of the light source can introduce diffraction degradation.
    Theoretically, that can be true. In practice, not so much. The enlargement factor is small and any degradation of the image will likewise be too small to notice unless you start examining the print with a magnifier.
    Frank Schifano

  7. #17

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    If one is using a smaller aperture with say a 4x5 inch print vs 16x20 from a given film format, the 4x5 print may have the larger effective aperture.
    Claire (Ms Anne Thrope is in the darkroom)

  8. #18

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    Quote Originally Posted by Doremus Scudder View Post
    Stopping down will increase the depth of focus ...
    Just as with a camera depth of field does increase as the
    lens is stopped down.

    I focus using strong reading glasses, both eyes open and
    the lens wide open. I fine tune the image until it is as
    sharp as can be then stop down. I know the image
    will be sharper yet for having stopped down. Dan

  9. #19
    jeroldharter's Avatar
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    I ordered some screw in B&W ND filters to fit my enlarging lens from Calumet. That definitely helps and solves the problem. Also, when I go from 8x10 up to 11x14 or 16 x20 I can adjust the ND amount and maintain about the same standard exposure times which I like.
    Jerold Harter MD

  10. #20
    ic-racer's Avatar
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    Quote Originally Posted by jeroldharter View Post

    I know everyone talks about alignment being so important .
    I have been there. Nothing like high magnification enlargements to bring out any weaknesses in the system.

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