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Thread: Times?

  1. #1

    Join Date
    Sep 2002
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    747

    I spent a little bit of time yesterday with my new enlarger. What I noticed was how long the times needed were. Thinking about it afterwards I think the issue might be that the bulb is much higher above the negative then my other enlarger. In 35mm mode the bulb must be almost 12" above the negative. Compare that with something like 3" with my other one. So even with the 150watt bulb it takes longer to make a print then the 75watt bulb in the other enlarger. Does this sound reasonable? I've got a new bulb on order and I really should have picked an easier negative but I'm curious.

  2. #2

    Join Date
    Sep 2002
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    38
    Robert, it's difficult to tell from your description whether your enlarger is a condenser type, or a diffusion type. A condenser type enlarger usually has a way to adjust the placement of the condenser lenses for maximum light output for each size format. Condensers allow a less powerful bulb to be used. They can focus the light into a stronger, narrower beam. A diffusion type enlarger uses the inside of the lamphouse as a reflector. It gives off a larger, wider beam of light. It takes a larger more powerful bulb. However, it usually needs heat absorbing diffusion glass between the bulb and the negative to prevent overheating the negative. If you were to use a large hot bulb too close to the negative, you may experience curling and/or cause permanent damage to the negative. There is always a trade off between the size of the bulb and the printing times. the larger bulb placed farther from the negative probably helps to avoid heat build-up, but printing times are going to be slightly longer.

  3. #3

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    Sep 2002
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    It's a condensor type. When it's setup for 35mm the bulb is a fair distance from the negative. I was just a little surprised at how great the times seemed to be. I actually stopped and decided to think about it. Which isn't a bad thing I guess.

  4. #4

    Join Date
    Sep 2002
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    15
    Curious, what brand is your new enlarger and what was your older or previous one? What is the actual difference in times? Same lense or different one?

  5. #5

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    Sep 2002
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    The new one is a 30+ year old beseler 4x5. The old one is a 20+ year old Omega B66. I wasn't thinking enough to use the same negative. Honestly I was just trying to make a print more then doing any real testing. Let me put it this way. I screwed up the first test strip by leaving the lens wide open. With the lens at F/2.8 16 seconds was almost enough time. With the other enlarger a normal negative takes between 8-12 seconds at F/5.6. Hopefully I'll have some time this weekend to try again.

  6. #6

    Join Date
    Sep 2002
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    243
    Are the lenses you are using different focal lengths between the two enlargers?

    Yes, if the negative stage is further away from the baseboard, the exposure times will be longer as light falls off rapidly (1 over the square of the distance).

    However, if you are using the same lens (same focal length), the distance should be close to the same between enlargers for making the same size print. Are you sure you have the condensers adjusted correctly for the format you are using in the Beseler 45? This can make a significant difference in where the enlarger head has to be positioned in order to focus the film on the easel.

    Also, you need to make sure the developer dilution and temperature are correct. If you have changed developer dilution, or the developer is cold (65F or lower), this can greatly affect how the developer acts. Both can cause longer exposure times to compensate for more dilute developer or colder developer.

    As to some of the other comments:

    “A diffusion type enlarger uses the inside of the lamphouse as a reflector.”

    Not necessarily. Cold light heads such as those made by Aristo have no lamphouse per se, but a series of tubes that form a grid above the film stage.

    “However, it usually needs heat absorbing diffusion glass between the bulb and the negative to prevent overheating the negative.”

    “If you were to use a large hot bulb too close to the negative, you may experience curling and/or cause permanent damage to the negative.”

    Not true with a cold light head or a Beseler/Minolta 45A type color head. Heat can be a problem with standard COLOR heads using tungsten – halogen lamps with mixing chambers (the type in general use most enlarger manufacturers).

    But, heat is usually not a problem with condenser enlargers. Also, a piece of “diffusion glass” (opal glass?) would only increase the problem as it would scatter the light requiring even longer exposure times. Heat absorbing glass is usually clear, with a dichroic coating on one side to REFLECT the infrared (IR) back into the lamp house.

    By definition (and especially with the Beseler 45 type enlargers) the lamp is separated from the film stage by the condensers in a condenser enlarger. The condensers absorb a great deal of energy in the 12 micron and above wavelength band (heat) because they are large, thick pieces of glass and glass in and of itself is a very good absorber of IR energy. This is why infrared video cameras must have lenses that are made from exotic materials like gallium arsenide, etc. as a glass lens will not pass enough IR energy to the sensor for it to operate.

    Secondly, the lamp in the Beseler is further isolated from the film stage by the upper bellows that do not absorb or transmit heat. I have never had a heat problem with my D2V with the metal condenser section that sits directly on the film carrier using a 150 Watt enlarger bulb and long exposure times making 16x20 prints from 35mm.

    From my experience with the Beseler 45 enlargers, with a 50mm lens it would not be unusual to have a 30 second or greater exposure time at f/8 making an 8x10 print. This is using Dektol diluted 2:1 with a 3 minute development time and making sure the developer is at 70F.

  7. #7

    Join Date
    Sep 2002
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    747
    I guess I should add a follow up. This Sunday I did three other negatives. The times were normal [at least what I'm used to]. Since I only changed the negative that leaves the first negative as the problem. I'm not really sure why. It doesn't look that bad-) I still wasn't smart enough to reprint an older negative. I've got enough new ones at the moment that reprinting olds ones is down the list.



 

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