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  1. #1
    kwmullet's Avatar
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    Cutting down exposure times w/Neutral density?

    I've got a Beseler 45MCRX enlarger with a rheostat-looking thing called a "Resistrol" that has a voltmeter on top which I can use to control the voltage to the lamp in my condenser housing. I've, uh, resisted using it so far because I suspect that if I change the voltage to the incandenscent bulb in my condenser, the color temperature would change along with it.

    Even with multigrade filters in place, with a 50mm lens all the way down to f16, I get print times of 30 seconds or so at 8x10. I'd prefer they be closer to a minute to make dodging easier. What's the prescribed way to lengthen exposure time without affecting performance of VC paper? If changing the voltage to the lamp changes the color temperature, that would likely change the contrast of my print as well. I've got a hefty-size tray in my condenser for CC filters. Do I need to buy some neutral density filters and put them up there? Does anyone know for sure that changing the voltage to the lamp up to a given point will NOT change its color temperature?

    It's occured to me to use a 75mm lens instead and crank the enlarger way up and get that extra time through the law of inverse squares, but I'd much rather keep my head where it is and change the intensity of the image somehow. I'd also rather not keep a dimmer bulb in the drawer for such occasions.

    As a sidenote, the serial# on my enlarger is 50354. Any way to tell when it was born?

    cheers,

    -KwM-

  2. #2
    David A. Goldfarb's Avatar
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    An ND filter is a perfectly good way to lengthen the exposure time. You could use an ND gel (even a lighting gel) in the filter drawer or condensor box or an optical quality ND filter on the enlarging lens. Many enlarging lenses have 40.5mm filter threads, but you can check the manufacturer's website to be sure, if it is a modern lens.

    Some enlargers also take different sized bulbs. For instance, if you have a 150 W bulb in there now, it may be able to use a 75 W of the same physical size.
    flickr--http://www.flickr.com/photos/davidagoldfarb/
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  3. #3
    L Gebhardt's Avatar
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    Using the 75mm lens will not change your exposure times. You are still focusing the same amount of light over the same area, so the time will be the same at the same f/stop. With the 75mm lens though you may get an extra stop or two to use. I think the smaller bulb is your best bet.

    You may also want to change the way you dodge and burn. I have generally found that 20 to 30 seconds works fine for me. I use Fred Picker's 3 second burst method now and I feel it has given me much more control over print manipulation. Before I felt that a minute was also better for more complex prints.

  4. #4

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    The Resistrol is where the "R" in MCRX comes from... it is a voltage regulator that was put on to adjust the intensity of the light source. It has been removed from later designs, available as an optional add on. Quite frankly, most folks I know that use the MCRX just leave the light at full setting...
    Your options for adjusting the exposure times are good ones, adjusting the light output will have an impact on your contrast, correctable by filtration adjustment. The use of a 75mm will result in increased exposure only because you will need to have the enlarger at a greater distance from the table for the same size enlargement. You also have the option of using different lights (PH212/150W, PH211/75W, PH213/250W) but as with adjusting the Resistrol, you will notice a change in overall contrast, not to mention negative popping from the high watt bulbs (also a relatively short life span togo along with them). You probably have all these suggestions in your toolbag already...
    As for the age of your baby... well... suffice to say that I have an MCRX that is numbered 50293, purchased new in 1974. Is yours blue, black, or grey???
    Good luck, Ray
    Do not question what you have not done, question what you will not try.

  5. #5
    kwmullet's Avatar
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    Happysnapper,

    cool on the serial#. I'll bet that'd put mine sometime during late Ford or early Carter, and while I was in middle school. Mine is a blue model. There's a picture at http://bellavestudio.com/kwm-enlarger.jpg. I think I'll look into getting a neutral density filter to go into the housing and just keep it there when the enlarger isn't cranked up high.

    Interesting for me that this model of Beseler is new to me. I used various public school, workplace, art center and US Navy darkrooms from about 1974 until 1986 when I experienced my Great IT Distraction from which I recovered a couple of years ago. Although I used other Beselers, I don't think I ever used one of the M series until now. When I was ebaying for the enlarger for this darkroom, I was hoping to get an Omega, but now that I've got this Beseler, I'm very glad I have it. I wouldn't have liked mucking about with all those lens cones. One day, I'll get my hands on a 3-lens turret for this Beseler and be in hog heaven.

    -KwM-

  6. #6

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    KW:
    Should be able to get ND material with relative ease, As I recall rosco made this stuff in 24" sq sheets. Try calumet/B&H/Adorama, anyone that sells pro lighting will know what you're asking for.

  7. #7
    kwmullet's Avatar
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    Cool, Shaggy. Thanks. (:

  8. #8

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    KW...
    The turret is a fun toy for about an hour... you will be better advised to just use individual lensboards for your separate lenses. They are more stable and much easier to tighten as needed and less obtrusive than that monster turret device. You would have money better spent on an anti-Newton glass negative carrier...
    You will really enjoy that enlarger. It is built like a tank and as long as you maintain it and keep it covered when not in use, it will be worth every cent you invested, tenfold! Beseler still uses the same design for the newer MX models with only slight variation on the placement of the screws mount to hold the thing together, I guess a minor tolerance allowance after years of using the same tap and die machines. In this day of constant obsolescence, that is rather remarkable. I do have quite a lot of time spent with that machine, holler if you have any questions!
    Ray
    Do not question what you have not done, question what you will not try.

  9. #9

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    Good Evening, KW,

    I don't think you'll ever regret having the MCRX. I've used mine for close to thirty years with no problem. As Happysnapper says, the Resistrol is rarely used at anything other than its full output setting. One exception for me has been the extremely rare circumstance of making a B & W negative from a color transparency. I remember turning the Resistrol back considerably to get a more convenient exposure time on the panchromatic film (probably T-Max 100) I was using. I've also, on a couple of recent occasions, tried making contrast masks for B & W negatives and found the reduced output useful. The voltage gauge on my Resistrol has been inoperative for years, but the Resistrol itself still works fine. As long as you shoot nothing larger than 4 x 5, the MCRX should be the last enlarger you'll likely need.

    Konical

  10. #10

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    printing with the Resistol.

    I am not at this time using a beseler. I am using a Durst condensor enlarger; However, I use an inexpensive bulb dimmer and a set my enlarging timer to standard time to expose my paper. I would imagine that the color temperature of the bulb changes. Since you are printing on VC paper I doubt that the change in color temperature will cause any problem whatsover.

    My reason for doing this are two: I use a 63mm 2.8 N series lens for my 35mm work. The best apeture is F4. I use glass in my carrier so film flatness is not a problem. Using a set time allows one to have a constant that you get used to for burning and dodging. With practice one develops a feel for the intensity of the projected image and increases or decreases the brightness for the initial test. I would image that those that use an enlarging meter would find this to be helpful also.



 

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