Two questions about enlarging

Discussion in 'Enlarging' started by David Lyga, Jun 9, 2013.

  1. David Lyga

    David Lyga Subscriber

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    I have an Axomat 5 35mm enlarger and it does all that I need done. But, for about three years I have had a 3" x 3" square of drafting film (available cheaply in any art supply store) inserted into the filter drawer in order to convert the light from condenser into diffusion. I like the really even results. (For focusing, I simply temporarily pull out the drawer so that more light will reach the easel.) Does anyone else like this simple method?

    Also, is it true that a blue light will result in slightly sharper prints, due to the fact that you now do not have to worry about all the various colors present in tungsten 'white' light needing to be focused? - David Lyga
     
  2. NedL

    NedL Subscriber

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    I only have a cold light, so don't know about the first part, but that's interesting.

    As for the blue light, I guess it wouldn't matter much for fixed grade paper and might matter very slightly for VC paper, since no lens is perfectly achromatic. I'm not sure how much UV or violet light gets through an enlarging lens ( and film! ), probably not much, but it might make more difference up at that end of the spectrum. Maybe someone has done a calculation to show that these aberrations are smaller than the "CoC" or grain size on paper....
     
  3. David Lyga

    David Lyga Subscriber

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    Ah, since 'no lens is perfectly achromatic' NedL this becomes all the more reason to be concerned with such lens' inability to focus all colors at the same time. Thus, by allowing ONLY ONE color, blue, to hit the paper maybe that deficiency can be solved. And maybe I am being naive here but I wanted to pose this in order to receive reaction. Thank you. - David Lyga
     
  4. NedL

    NedL Subscriber

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    Hi David,
    You like to ask "provocative" questions, to provoke thought, I mean! So I'll add to your question. When we look at the world with our own eyes, in color, presumably the lenses in our eyes are not perfectly achromatic either. Our brains probably use the color variation to enhance our perception of patterns and edges and textures etc... So perhaps if we could make a print using perfectly monochromatic light, perfectly focused, it would look less natural and lose information compared to the "micro-blur" in the gradation of tones caused by slight chromatic aberration? In other words, would this kind of sharpness be too much of a good thing at the expense of important contrast? Perception of sharpness is more than resolution... it's not obvious to me that a perfect monochromatic projection would appear sharper!
     
  5. tkamiya

    tkamiya Member

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    Microscopists use this principle of using blue light, light with shorter wave length, to obtain the sharpest image possible. BUT, they are looking at objects at 1000x magnification and trying to extract finer resolution at that extreme magnification. They also use Apochromatic lens so that convergence error is minimized. But again, they are worried about it at an extreme magnifications.

    B&W paper is already mostly sensitive to blue/green spectrum only. Magnifications we are talking about isn't nearly as extreme either. Provided that you are using quality lens, I doubt it'll make any visible difference.
     
  6. polyglot

    polyglot Member

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    If you use only blue light on VC paper, you will get an extremely high contrast image. You also need some green light to activate the lower-contrast layer(s) and thereby get an appropriate image.

    For any quality 6-element enlarger lens, the focal differences due to wavelength are not an issue. You should be able to make prints of the grain from slow fine films.
     
  7. ac12

    ac12 Member

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    I recall a similar method to diffuse the light in a condenser enlarger.
    I think they used a piece of frosted/ground glass or a piece of white plexiglass (which also soaked up more light than the frosted glass).
    I don't know why I did not try it myself.
     
  8. dorff

    dorff Member

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    Well, I am sure your approach will make it a bit easier to print from slightly scratched negatives. That is one of the main reasons a diffuser source is preferred over a condenser source. As for blue light: If you use VC paper, it will simply give you the highest contrast the paper is capable of. So you would have to use graded paper. Not in principle a problem, but then you can use any pure colour, and get into the part of the spectrum to which the paper is most sensitive. It might be that colour is blue, I don't really know. Green would be better for your eyes to work in. I would only do this if my enlarging lens was not very good. I don't have that problem, since I use Nikkors, Rodenstocks and Componons. They are all good enough that I don't have to bother with monochromatic light. Given the hassle of working with graded paper, a decent enlarging lens seems a cheaper and more efficient solution.
     
  9. LJH

    LJH Member

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    In one of his videos on YouTube, Clyde Butcher is shown enlarging with blue light.
     
  10. Richard Jepsen

    Richard Jepsen Member

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    I used to use a frosted cut glass above the condensers in a Omega B-22. It added about 50% to the print times and lowered the contrast by no less than 1/2 grade. The concept works.
     
  11. David Lyga

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    NedL: you are asking a philosophical question to a person not properly versed...

    It would seem to me that, here, in this instance, the human brain (flawed as it is) nevertheless sets the 'standard' of perfection as far as proper hues go. But, on the other hand, it would also seem to me that acutance is not relative, but absolute, in measurement. (How could it NOT be, as it is essentially mathematical?) It would be interesting to see if I am agreed with or refuted but I plead ignorance here.

    Here is the source of my original query: The Amateur Photographer's Handbook by Aaron Sussman, 8th revised edition, 1973. Page 526, Hints and Suggestions #46:

    - David Lyga
     

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  12. MattKing

    MattKing Subscriber

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    David:

    With respect to the colour of the light, the issue is that a simple lens (such as a magnifying glass) will focus different colours of light to different distances. More complex lenses can and are designed to correct for this - in some cases exceptionally well.

    A basic, three or four element enlarging lens is probably not highly corrected for this, but there is some correction built into the design. Higher quality five, six or more element enlarging lenses will most likely be highly corrected for the problem.

    So if you use a good quality enlarging lens (Componon, Rodagon, Nikkor) at typical enlargement amounts (full frame, 5 x 7 through 11 x 14 or 16 x 20) this shouldn't be a problem for you. If you are making very large enlargements, you may need to use the higher range APO lenses to avoid the problem.

    You need to realize, however, that even if you use the basic lenses, there is another factor to consider. There is a certain amount of depth of focus at the paper plane available to you when enlarging, and any focus shift that falls within that depth of focus will tend to be almost invisible in the result. So, in most cases, stopping down the basic lenses will also help avoid the problem.

    I would guess that the target market of Mr. Sussman's book was most likely the hobbyist photographer in the late 1960s, early 1970s. Top quality enlarging lenses were probably fairly rare in that market, at that time.
     
  13. David Lyga

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    No, top quality Nikkors were readily available and not too expensive: about $35 then (1973) for the 4/50, though, of course, it was not apo. The Sussman book was full of interesting information but, true, did not delve fully into theory like the British books did and do.

    MattKing: for what I do, the sharpness if fully adequate: My argument was more theoretical than practical and the 'suggestion' that was in the book piqued my interest, as we are all looking for sharper and sharper results. It was worth bringing up the topic, if only to cause thinking. - David Lyga
     
  14. dorff

    dorff Member

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    The demands on a camera lens is somewhat greater than the demands on an enlarging lens, because the visible light spectrum is considerably wider than that which enlarging paper is sensitive to. In my view the more expensive lenses fix other problems, such as field curvature, distortion and vignetting, to a greater degree than the three element lenses. Those are perhaps more important for ultimate sharpness and print quality than the apochromatic design. All paper will be sensitive to green/blue light, and if you can find a narrow band pass filter in that part of the spectrum it would make your results sharper. But that approach cannot fix all the other problems inherent to simple optical designs, and cannot make them look like $500. They will still distort, focus in a curve rather than a plane, vignette etc.

    The above notwithstanding, I think there may be darkroom printers who derive enough benefit from such a technique to justify the hassle. For most of use, though, getting a fraction more resolution makes little difference. One has to optimise every part of the image making process to see it culminate in sharper images. That means sharpest lenses at optimum apertures, rock solid support and fast shutter speeds, optimal development i.e. non-solvent, very fine-grained film, and so on. And then printing huge, certainly larger than 16"x20". How many of us really give attention to the point of obsession, to every part of that equation? I doubt many. We all rather focus on the image and its message, and do the best we can under the circumstances with the rest. Some images succeed because of their resolution when printed large, but those are somewhat in the minority in my view. Other images succeed because they have general visual impact.
     
  15. David Lyga

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    True, dorff, this never ending search for resolution CAN be obsessive, and, as the eminent Roger Hicks once said: smaller prints are more 'intimate'. How correct he was and is. - David Lyga
     
  16. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

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    David , I think you should think about there is art in designing these papers , films and lenses. If it is designed for wide spectrum bulb , it would be needed to be used as it is. I think blue light use is similar to print a bw advertisement on a luxury magazine with cyan separation. Good art director uses cmyk bw print.