75mm enlarging lens vs 50mm

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Hi, I have a friend who is getting rid of a very nice 75mm Rodenstock lens. He has offered it to me at a very good price. Right now I only work in the 35mm format and use a "normal" 50mm lens for all my printing. If I were to put the 75mm lens on my enlarger what could I expect? Would the overall projected image be larger? Or perhaps smaller? Thanks!

-- Justin Fullmer (provo.jfullmer@state.ut.us), January 22, 2002

Answers

I will be smaller, which can be very useful. Using 35mm negatives, I replace my 50mm lens with a 75mm lens for 5x7, and smaller, prints because it gives me considerably more room for focussing, dodging and burning. With my enlarger, I have to elevate the easel in order to focus 4x5 prints from 35mm, and so the 75mm lens makes it a lot easier to print these sizes since I can keep my easel on the baseboard where it belongs.

-- Ted Kaufman (writercrmp@aol.com), January 22, 2002.

I've used a 75mm for most work for years. I only dig out the 50mm when I need to make a particularly large print from a 35mm neg. I don't think you can go wrong with the Rodenstock.

-- Ed Buffaloe (edb@unblinkingeye.com), January 22, 2002.

Depends on a number of factors. The Rodenstock Rodagon line is excellent, however some of the other Rodenstock’s (Rogonar, etc.) are of lesser quality. Obviously, it also depends on what brand and line of 50mm lens you are comparing it to.

The problem of maximum enlargement on the baseboard has already been mentioned. Other factors include the optimum enlargement factor of the lens. Many 75mm lenses are optimized for about 4x enlargement, but many 50mm lenses are optimized for 10x. The closer you are to optimum enlargement factor of the lens, the better the resolution and flatness of field. To make an 8x10 print from a 35mm negative requires about an 8.5x enlargement factor (without any cropping).

All other things being equal, the lens with the largest image circle (in this case the 75mm) will have better resolution because it will be using only the middle portion of the lens, as compared to the 50mm lens that relies on edge-to-edge sharpness to cover the entire negative. The sharpness of a lens is usually lower at the outer 1/3 of the image in comparison with the middle.

So the missing link here is the exact models of the 50mm and 75mm lenses you are comparing. For example, I would choose the El-Nikkor 50mm f/2.8 (but not the f/4) over the Rodenstock Rogonar 75mm lens.

-- Michael Feldman (mfeldman@qwest.net), January 22, 2002.


You don't mention if you are using a condenser or diffusion (cold light & color head or VC head are diffusion types) light source. If you are using a condenser you must change condensers to focus the 75. With an Omega (B series mostly)you must remove the thick top condenser & replace it with a thin condenser OR if the enlarger has a V (as in D2V D5) in its name you adjust the focal length of the condenser array. If you own a Bessler you adjust the condenser by changing the distance between them by a bellows adjustment. I believe the other brands use a system similar to Omega but I only have personal experience with Omega B series & Bessler 23C.

-- Robert Orofino (minotaur1949@iopener.net), January 23, 2002.

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