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  1. #1
    BetterSense's Avatar
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    Confused about focal lengths and bellows draw

    I have an Omega D2 for printing 4x5 negatives. I have a 135mm lens. I can just barely print an 8x10, if I loosen my lens several turns for more extension. Any smaller, and my bellows racks all the way out before I obtain focus. So if I want to print a 5x7 from 4x5 right now I can't.

    My first instinct is "Oh, I need a longer lens, then the baseboard image will be smaller". But wouldn't a longerr lens need MORE bellows draw? Or would a longer lens force me to put the enlarger higher, paradoxically resulting in less bellows draw (real focal length)? This is confusing my brain.

    Also, has anyone ever printed medium format and/or 35mm with the 4x5 condensers in place? I understand that they make special condensers for smaller formats but I'm having a hard time understanding why, considering that if it works for 4x5 it shouldn't work the same for 35mm, considering 35mm is basically a crop out of a 4x5 negative.
    f/22 and be there.

  2. #2
    David A. Goldfarb's Avatar
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    A 135mm lens on an Omega D2 should be on the medium sized cone (around 2 inches) if I remember correctly. It sounds like you probably have it on a flat lensboard. That would be your problem.

    The original D-II, which I have, only came with the option of 4x5" condensers, and smaller format and variable condensers came into place later.

    The main purpose of the condensers is to produce even illumination across the negative, and in this regard, you should have no trouble using condensers for a larger format when enlarging a smaller format negative. Having condensers matched to the format would give you more efficiency (brighter illumination) with smaller formats, but in my experience the difference isn't enormous. (Of course you can't use a condenser designed for a smaller format with a larger format neg, or you won't illuminate the whole neg evenly).

    Another issue that some people think is important is the role the condensers play in the collimation of light in the system, and if this is significant, then condensers that are well matched to the format and focal length of the enlarging lens could produce sharper prints, more like a point source enlarger, so Durst, for example, offers a wide range of condenser sets for different enlarging lenses and formats. I could see this being important, if you were making a lot of enlargements to the same size, and the condensers, format, and enlarging lens were matched for that specific reproduction ratio, but change the magnification ratio without adjusting the condensers accordingly, and as I see it, the system is no longer matched, so I'm a bit dubious about matching condenser lenses closely to format in general for the purpose of improving sharpness.

    And in any case, I prefer cold light.
    flickr--http://www.flickr.com/photos/davidagoldfarb/
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  3. #3
    BetterSense's Avatar
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    May I ask, why do you think cold light better? Is it just because cold light heads tend to be diffusion heads? I don't even know if that's true I'm just wondering about cold light heads. All I know about them is they use fluorescent tubes, which would keep heat down in the darkroom.
    f/22 and be there.

  4. #4
    David A. Goldfarb's Avatar
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    Less spotting and a smoother look with diffuse light sources. Ansel Adams also explains in The Print that diffuse light sources reduce the Callier effect, which can cause high values to become blocked, which I haven't attempted to sort out for myself, but I like the look.

    Condensers produce sharper grain than diffuse light sources, if you like that.
    flickr--http://www.flickr.com/photos/davidagoldfarb/
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  5. #5

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    Check into the Aristo VCL4500. I've used one for many years and have found it to be very worth-while. They are not cheap but you don't need different paper grades and can easily vary the contrast within an image ( multigrade paper ).

  6. #6
    BetterSense's Avatar
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    They are not cheap but you don't need different paper grades...
    Do you mean that with a cold-light head, you can vary the contrast of graded paper?

    and can easily vary the contrast within an image ( multigrade paper)
    I don't quite understand this.
    f/22 and be there.

  7. #7

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    Quote Originally Posted by BetterSense View Post
    Do you mean that with a cold-light head, you can vary the contrast of graded paper?
    With SOME cold light heads, you can vary the color mix of the light. This does the same thing as the variable contrast filters. So you can vary contrast of VC papers.

  8. #8

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    The Aristo has 2 bulbs, one blue and one green. There are three different modes and you can dial in the contrast grade when using multigrade paper. A "plain" cold light would require using variable contrast filters. www.aristgrid.com

  9. #9
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    Quote Originally Posted by David A. Goldfarb View Post
    ...Ansel Adams also explains in The Print that diffuse light sources ... can cause high values to become blocked, which I haven't attempted to sort out for myself, but I like the look...
    That's possibly the only misinformation AA ever distributed. There is no difference in tonality or gradation between both types of enlarger if the negative was developed accordingly. Yes, a condenser will block the hightlights in a negative developed for a diffuser, but not if the negative was developed for the condenser.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  10. #10

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    sorry for the error it is www.aristogrid.com

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