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  1. #21
    RalphLambrecht's Avatar
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    Quote Originally Posted by BetterSense View Post
    Why glass in the first place, with smaller formats? There seems to be plenty of dof on the enlarger at f/8 or so with smaller formats, and 4x5 seems to stay perfectly flat under its own stiffness. Are you all making big prints that necessitate large apertures or glass to prevent the negative from warping?
    A truly sharp print only comes from a negative that is sandwiched between glass. Depth of focus is not enough to cover negative curl, sagging and heat popping sufficiently. This is most important for smaller formats. For example, a 35mm negative setup to make an 8x10 print at f/8 has a DoF of just 0.4 mm!
    Regards

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

  2. #22
    BetterSense's Avatar
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    Why is it that I can see sharp grain, then? If I can see sharp grain all across the print, then how could it be any sharper? I'm just wondering. None of my negative carriers has any glass, and the commonly available negative carriers one finds on ebay for say the beseler 23C are all glassless. Is it possible to retrofit a negative carrier to be glass-type?
    f/22 and be there.

  3. #23

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    Depending on the neg carrier, yes it is possible to retrofit it. A 1/8" thick aluminum one can have a recess milled out to use AN and regular glass from a GEPE 6x6 slide mount. Neg warping can depend on the image and the size of the enlarger bulb.

    I've got a set of 35mm negs of a narrow plume type waterfall shot in bright sunlight, they bow downwards in a couple of seconds in a single an glass carrier in a 4x5 durst enlarger with a 250 watt colour head with a 1/4" thick heat absorbing glass, but are fine in a similar carrier in a 150 watt condenser enlarger.

  4. #24

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    Quote Originally Posted by BetterSense View Post
    Why is it that I can see sharp grain, then? If I can see sharp grain all across the print, then how could it be any sharper?
    Don't worry about it, then.

    When I started, I used a fairly low watt enlarger, a Philips PCS2000. I used glassless negative carriers. When I replaced the Philips with a big De Vere, I found that the added heat caused the negative to bow up with glassless carriers. So I do what Ralph suggested. I use AN glass on top of the neg, and a glassless insert on the bottom, at least with roll film. With 4x5, I use a full glass carrier.

  5. #25
    Chazzy's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    A truly sharp print only comes from a negative that is sandwiched between glass. Depth of focus is not enough to cover negative curl, sagging and heat popping sufficiently. This is most important for smaller formats. For example, a 35mm negative setup to make an 8x10 print at f/8 has a DoF of just 0.4 mm!
    You're the expert, and I'm willing to take your word for it, but it doesn't make sense to me. Since the glassless carriers for larger formats necessarily have larger holes in them, it would seem that the larger the hole, the greater the opportunity for sagging to occur. Beseler seems to acknowledge this by producing the Negaflat carrier for 4x5 sheet film, and I have noticed that at least one other company has a carrier which tries to stretch sheet film negatives.
    Charles Hohenstein

  6. #26

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    Lots of good answers. The reason I am thinking of using an anti newton glass is because my enlarger has a full glass carrier and I thought that it would be simple enough just to put an AN top glass in and get flat negs with no newton rings. I have never used AN glass before and was sure it would be ok until I saw some pics on the net with the AN glass printed as well as the image! Maybe it was bad focusing. I have some Aumet 35 glassless inserts and Bimena 6x9 but no 6x6 (although I may just make some). I just didn't want to blow cash on the AN if it was no good but it seems that it is fine.


    dave

  7. #27
    RalphLambrecht's Avatar
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    Quote Originally Posted by Chazzy View Post
    You're the expert, and I'm willing to take your word for it, but it doesn't make sense to me. Since the glassless carriers for larger formats necessarily have larger holes in them, it would seem that the larger the hole, the greater the opportunity for sagging to occur. Beseler seems to acknowledge this by producing the Negaflat carrier for 4x5 sheet film, and I have noticed that at least one other company has a carrier which tries to stretch sheet film negatives.
    You are right to question it. The 35mm negative is sensitive, because it has a natural curl, it's thin and sensitive to heat. That does not mean that the 4x5 negative does not have its own set of problems. You already mentioned the large opening and the need to lightly clamp the negative to keep it from sagging. However, a large negative has the advantage of less magnification required to make the same-size print. As I said earlier, at f/8 an 8x10-inch print from 35mm film has a DoF of just 0.4 mm. To make the same-size print from a 4x5 negative at the same f/stop you get luxurious 2.1 mm of DoF.

    In any case, I highly recommend glass at least on one side of the negative carrier, and prefer to have the negative sandwiched. I happily put up with cleaning and spotting to have a perfectly flat negative to print with.
    Regards

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

  8. #28
    Martin Aislabie's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    I thought it was the other way around. Newton rings form in too dry conditions and a humidifier actually helps. Have I gotten this wrong?

    Dry would explain the winter months!
    Ralph, I don’t know if you get Newtons Rings in very dry conditions – I have no experience of such a phenomena

    We (in the UK) get Newtons Rings in the very damp conditions we get in the winter – as the Neg sits in the Enlarger warming up.

    For a few days each winter, when the conditions are just right, I can even get Newtons Rings, despite using Anti Newton Ring Glass and an IR Filter – I guess I am just “lucky”

    The damp(ish) Neg as it warms up “sweats”, some of this moisture is then trapped in the small parallel gap between the flat supporting layer of the Neg and the flat (plain) glass.

    Light passing through this uniform layer of moisture Diffracts and hence you get Newtons Rings.

    If the glass on the side of the Support Layer in the Neg Carrier has an uneven surface, then a non-uniform layer of moisture builds up and the uniform Diffraction (which we see as Newtons Rings) cannot occur.

    That I why the Anti Newton Glass has an irregular surface and as the Emulsion side of the Neg has its own uneven surface, why the mating lower glass can be plain.

    Martin

  9. #29
    Martin Aislabie's Avatar
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    Quote Originally Posted by Chazzy View Post
    You're the expert, and I'm willing to take your word for it, but it doesn't make sense to me. Since the glassless carriers for larger formats necessarily have larger holes in them, it would seem that the larger the hole, the greater the opportunity for sagging to occur. Beseler seems to acknowledge this by producing the Negaflat carrier for 4x5 sheet film, and I have noticed that at least one other company has a carrier which tries to stretch sheet film negatives.
    The other thing to remember, is that Sheet Film has a much thicker and stiffer backing /support layer than is used for Roll Film

    With Roll Film, the Support Layer needs to be thin and very flexible - to allow it to be tightly wound around a small diameter reel and fitted inside a small outer casing

    The sole purpose of this support layer for Sheet Film is to remain flat and rigid.

    I can Enlarge my 5x4 Negs without needing to resort to a glass Neg Carrier.

    However, I am not so sure I would get away with it if I were trying the same thing with 10x8

    Martin

  10. #30

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    I live in a very dry climate and only get Newton rings when the humidity in my darkroom reaches 50% or when I print negatives I've just processed and dried. My solution, without A/N glass, is to heat the negative with a hair dryer to dry it completely and place it in a warm carrier. With this procedure, I never get Newton rings. I wasted a lot of paper until I learned this. I believe that all negatives should be printed between glass if ultimate sharpness is important and the bottom glass should be very thin and of optical quality.
    Denise Libby

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