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  1. #1
    David Lyga's Avatar
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    Negative stage design

    It would be interesting to see what feedback this warrants. I am talking about 35mm format here:

    Is the enlarged image quality best served by 1) allowing a glass plate to touch the top of the negative and thus keep it flatter (at the real expense of introducing some possible 'in focus' dust) or 2) is it better to be able to use a traditional negative carrier in which nothing touches either the top or bottom of said negative (thus allowing a slight curvature to result on the top of the negative)?

    The Leitz Valoy and the Durst M301 utilize the first design and most other enlargers (especially Japanese) utilize the second design. Personally, I cannot find any comfort using the first as the introduction of that other surface to keep immaculate greatly bothers me. The slight curvature that might result from not allowing any glass to touch the upper portion of the negative can be greatly mitigated, even eliminated, by stopping the enlarging lens down. But is there any real validity to the first approach that I am not seeing? I recently turned down an enlarger (Durst M 301) because of this. - David Lyga.

  2. #2
    hpulley's Avatar
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    I have an old Durst M-300. It has a glass negative carrier but I rarely find dust problems with that, instead it is dust on my negatives I need to work on. I simply blow off all surfaces before I begin. It's the only style I've ever used so perhaps I don't know what I'm missing. I am looking at an M-605 soon which I think is the same design.
    Harry Pulley - Visit the BLIND PRINT EXCHANGE FORUM

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  3. #3
    Mick Fagan's Avatar
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    If you wish for optimal quality, then two sheets of glass is a virtual requirement, regardless of format.

    That said I don’t use glass too much these days, but in another life working in a pro lab, glass was the go.

    If you wished to enlarge 135 to 20x24” then you had to use glass. Enlarging 135 to 24x30” or larger you need an optimally aligned enlarger, otherwise you will find very noticeable out of focus fall-off in all corners and along the long edges of the negative frame.

    You can get away with using removable magic tape on either side of a 135 film to stretch it slightly. I use this technique, on every negative I enlarge without glass.

    Mick.

  4. #4

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    Depending on how much burning etc the print requires, and how long the basic exposure is, the curvature or waviness of the negative in a glassless carrier can become an issue due to heat buildup at the negative stage, which causes the negative to bulge upward. I've done alot of experimenting with this lately. Stopping down the lens obviously helps compensate for negative curvature, but you don't have much tolerance there, and stopping down also increases the exposure time, which increases the tendency for the negative to curve/bulge. And I have found this to be an issue even if the enlarger has heat absorbing glass below the bulb. The negative receives less heat in my LPL diffusion enlarger, but it can still pop.

    For maximum sharpness ideally the negative should be sandwiched between glass on both sides. However due to the additional surfaces this introduces for dust, most people have found a good compromise by using glass only above the negative. This works pretty well since the tendency is for the negative to bulge upward. As for dust, I have not found this to be much of an issue. Just keep everything clean, give the negative and glass a blast of air, and get the glass on top of the negative as quickly as possible after blowing off the dust.

  5. #5
    Nicholas Lindan's Avatar
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    For ultimate image quality with an APO lens you need to use the lens close to wide open and thus need a glass carrier as there is close to no depth of field. Another consideration is negative popping and unpopping which are greatly mitigated by glass carriers.

    The arrangement with the bottom of the condenser providing a 1/2 glass carrier is a good compromise between dust problems and flatness. If you keep the negatives clean the glass stays clean. Glass carriers that leave the enalrger are prone to picking up dust when put on the table to load negatives. Additionally a full glass carrier has four dust collecting surfaces while the condenser-as-carrier design only has one.
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  6. #6

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    Quote Originally Posted by David Lyga View Post
    ... The slight curvature that might result from not allowing any glass to touch the upper portion of the negative can be greatly mitigated, even eliminated, by stopping the enlarging lens down. ...
    Your comment above is true, but is also the problem. If you stop down enough to get the depth of focus to cover the negative curvature, then you are reducing the crispness of the image by diffraction.

    I was enlarging 35mm to 11x14" a couple nights ago and noticed the edges and corners of my print had very slightly mushy grain. I was worried that my enlarger had gone out of alignment, but simply putting the negative into a glass carrier made the grain crisp to the corners at my printing aperture of f 5.6. With the glassless carrier I was preheating my negative to pop it before the actual exposure, so it was stable, just not flat.

    Glassless carriers are a convenience when they give you sharpness adequate to you needs, and they often do.

  7. #7

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    The Leitz and Durst enlargers you mention are particularly notable for their sharpness. Flatness does count. But 35 mm negatives are small, and most of the glassless carriers do a good job of keeping all but the most badly curled negatives flat. A few designs allow a badly curled negative to push the flaps of the carrier open, thus defeating its purpose. With either design, you have to be careful about the potential of the carrier scratching the film as well. Glass carriers require regular cleaning, but dust is really not much of a problem with them.

  8. #8
    David Lyga's Avatar
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    Mike Fagan, your reply offers the answer to my dilemma: using magic tape on each long side (sprocket sides) to force (by pulling) the negative to stay quite flat. Theoretically, this will STILL not be as flat as 'the glass alternative' but the exceptional advantage of not having anything touching that negative, despite naysayers out there, gives at least one of us a greater sense of security. Thank you. Pragmatism in darkroom matters is too scarce a commodity. Routinely going 'by the book' can sometimes prevent this from happening. And I think that the magic tape would also aid with potential popping (which I never experience with heat absorbing glass). - David Lyga

  9. #9
    Bob Carnie's Avatar
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    what mick says

    Quote Originally Posted by Mick Fagan View Post
    If you wish for optimal quality, then two sheets of glass is a virtual requirement, regardless of format.

    That said I don’t use glass too much these days, but in another life working in a pro lab, glass was the go.

    If you wished to enlarge 135 to 20x24” then you had to use glass. Enlarging 135 to 24x30” or larger you need an optimally aligned enlarger, otherwise you will find very noticeable out of focus fall-off in all corners and along the long edges of the negative frame.

    You can get away with using removable magic tape on either side of a 135 film to stretch it slightly. I use this technique, on every negative I enlarge without glass.

    Mick.

  10. #10
    RalphLambrecht's Avatar
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    Quote Originally Posted by Nicholas Lindan View Post
    For ultimate image quality with an APO lens you need to use the lens close to wide open and thus need a glass carrier as there is close to no depth of field. Another consideration is negative popping and unpopping which are greatly mitigated by glass carriers. ...
    That's my recommendation too!
    There might be another 'sweet spot' with non-APO lenses, rather than wide-open, but ultimate focus accuracy is only achieved with glass carriers.
    Regards

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

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