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  1. #21
    Helen B's Avatar
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    Um, strictly speaking... condenser lenses focus the light onto/into the objective lens, not the negative. That's why you need different condenser lenses for different formats - but only if the focal length of the objective lens changes (the light needs to be focussed at a different distance from the negative for a 105 mm lens than for a 50 mm lens, for example). Of course, the condenser lenses also need to be physically bigger than the format they are designed for.

    The matching of condensers to objective focal length (and the adjustment of the focal point of the condenser lens) is important if you wish to achieve even illumination.

    Diffusion heads don't need matching to different formats/objective lenses in the same way.

    Best,
    helen

  2. #22
    Helen B's Avatar
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    ... and nobody's mentioned the so-called 'Callier Effect' yet? But does it exist?

    A good part of the reason why condenser enlargers generally produce more contrasty images?

  3. #23
    lee
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    Hi Helen,
    I can't prove the Callier Effect exists but I think it exists. There are those that will disagree with that last statement.

    lee\c

  4. #24
    rbarker's Avatar
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    Quote Originally Posted by Helen B
    ... and nobody's mentioned the so-called 'Callier Effect' yet? But does it exist?

    A good part of the reason why condenser enlargers generally produce more contrasty images?
    My old Omega D2V didn't come equipped with Callier ID, so I'm not sure.

    I've always just thought of the difference as being similar to using a fresnel spot versus a big softbox. The spot (condenser) produces hard shadows (the sharp, contrasty image on the paper), while the diffuser/dichroic/cold-light produces softer shadows due to the light "wrapping around" the film grains.
    [COLOR=SlateGray]"You can't depend on your eyes if your imagination is out of focus." -Mark Twain[/COLOR]

    Ralph Barker
    Rio Rancho, NM

  5. #25

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    Quote Originally Posted by lee
    Hi Helen,
    I can't prove the Callier Effect exists but I think it exists. There are those that will disagree with that last statement.

    lee\c
    It sure does............appear to. The mechanism seems logical enough and you cannot argue with prints compared side by side! My diffuser is very soft and If I can print on G2 with it, the condenser will be running at G0, perhaps even G00. The contrast divide does not seem constant to me either, sometimes the difference is 1 grade, others times more, perhaps th highlight (dense silver) component dictates.

  6. #26

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    I'm sure SchwinnParamount is now thoroughly confused

    Condenser lenses collimate the light; that is, they get all the photons marching in a straight line. Diffusion enlargers send light through the negative at all different angles.

    The Callier Effect, as I understand it, deals with light striking a medium, i.e. the negative, from a directional source. One would hope, with a properly exposed negative, that as density increases, the amount of light passing through the negative decreases proportionally. The Callier Effect says, though, that this relationship becomes skewed, and with particularly dense areas of a negative, proportionally very little light is passed through. So, your shadows get darker and darker, but you still don't show much highlight detail. Hence, "blown" highlights. No "glow." "Chalk and soot."

    I don't know why light striking at multiple angles, as in a diffusion source, passes through the negative better than a directional source, but apparently it does.

    That being said, Schwinn, museums are full of fine prints made on both types. It's really a matter of gearing your process to the equipment.
    "If You Push Something Hard Enough, It Will fall over" - Fudd's First Law of Opposition

  7. #27

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    Quote Originally Posted by Helen B
    Um, strictly speaking... condenser lenses focus
    the light onto/into the objective lens, not the negative.
    That is true for one condition. The lens must be positioned so
    that it is at the focal point of the condensers. If the lens be
    racked up or down any amount than that is no longer true.

    I think this to be the case. The lens must not be positioned
    beyond the condenser focal length. I've a 105 on my Omega
    B8 and have the long focal length condensers installed. At
    full extension the lens is at or a small fraction of an inch
    shy of the condenser's focal length. So, the lens falls
    at or within the condenser focal length at all times.

    I think it may have already been said, in effect, that smaller
    formats may be printed with long focal length condensers
    and a short focal length lens. If one wishes to tighten
    that condenser beam for a brighter projection add a
    supplementary lens; at least for many Omegas.

    An easy test may be made. Let me know if interested. Dan

  8. #28
    Helen B's Avatar
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    'That is true for one condition. The lens must be positioned so
    that it is at the focal point of the condensers. If the lens be
    racked up or down any amount than that is no longer true.'


    Often the lamp height can be adjusted easily and left in the position appropriate for the majority of the work you do. At least that's how I do it. How much tolerance there is depends a lot on the type of lamp (point, clear, opal).

    'I think it may have already been said, in effect, that smaller
    formats may be printed with long focal length condensers
    and a short focal length lens.'


    Maybe it's worth checking for even illumination at the working aperture if you have a mismatch - most of the time things will be OK though. Results seem to vary depending on the lenses and lamp in use.

    I mentioned the Callier effect by posing rhetorical questions rather than launching into yet another of my irrelevant, confusing speeches. Maybe I should have said "Does it really exist in enlarging?" Ctein presented some thought-provoking evidence in two articles on the differences between diffusion and condenser heads in the Jan/Feb and March/April 1999 issues of PT.

    Best,
    Helen

  9. #29
    SchwinnParamount's Avatar
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    Quote Originally Posted by Doug Bennett
    I'm sure SchwinnParamount is now thoroughly confused

    Condenser lenses collimate the light; that is, they get all the photons marching in a straight line. Diffusion enlargers send light through the negative at all different angles.
    ...
    . So, your shadows get darker and darker, but you still don't show much highlight detail. Hence, "blown" highlights. No "glow." "Chalk and soot."
    ...
    That being said, Schwinn, museums are full of fine prints made on both types. It's really a matter of gearing your process to the equipment.
    My eyes started glazing over until I read 'collimate' and my ears perked up. I know what that means from one of my physics classes at Berkeley so many years ago. Actually, your mention of 'chalk and soot' strikes a familiar chord here. I have too many negatives that I can't milk more than chalk and soot out of. Sounds like a diffusion light source is the way for me to go. I'll keep my condensors on the shelf and use them in the right situation.

    I'm going to pick up the cold light head tomorrow (Aristo if memory serves) and let you all know what comes of it for my prints

  10. #30
    rbarker's Avatar
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    Quote Originally Posted by SchwinnParamount
    . . . I'm going to pick up the cold light head tomorrow (Aristo if memory serves) and let you all know what comes of it for my prints
    Aristo makes two types of cold-light heads - a single lamp for graded papers, and a dual tube unit for VC papers. So, if you use VC papers, be sure to get the right one. Also, look into compatible control and timer units. Because the light output can vary, the special timers often have light probes to sense the variations so it can adjust exposure time accordingly.
    [COLOR=SlateGray]"You can't depend on your eyes if your imagination is out of focus." -Mark Twain[/COLOR]

    Ralph Barker
    Rio Rancho, NM

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