I plan on purchasing an APO lense and am interested in any comparisons that have been done between the APO Rodagon and the APO Componon-HM. Thanks, Jim Stanford

-- Jim Stanford (jdstan@airmail.net), July 21, 2001

Answers

Are you talking 35mm or medium format? In 35mm, I don't think you're going to see enough difference to justify the expense of APO over the regular lenses. I think the nod goes to the plain, old Rodenstock Rodagon 50. (In APO, Rodenstock also takes the cake.)

In 120 format there is more of a difference, and I think the winner is the Schneider APO 90mm f/4.5, which achieves its best MTF scores at f/5.6 vs f/8 for the Rodagon APO. By the way, this lens is available from Robert White for $400-something instead of $600- somthing at B&H.

-- Brian Hinther (brianh@onewest.net), July 22, 2001.

"the winner is the Schneider APO 90mm f/4.5, which achieves its best MTF scores at f/5.6 vs f/8 for the Rodagon APO"

Why is achieving best MTF at f/5.6 an advantage? I would prefer to use a smaller aperture to ensure proper focus of the image. At f/11 my typical exposures are about 12 seconds using an Aristo cold light head. Even then, the voltage to the cold light head has been throttled back at bit using a Zone VI Cold Light Stabilizer.

-- Michael Feldman (mfeldman@qwest.net), July 23, 2001.

Would I be right in inferring from this that, if I use f8-f11, the Rodenstock would give me the best results?

-- Ed Hurst (BullMoo@hotmail.com), July 26, 2001.

Does anyone know where one can find comparitive tests on enlarger lenses?

I've heard great things about Fujinon enlarging lenses, particularly the EP and EX series. How do they stack up against the best from Rodenstock, Schneider and Nikon?

-- Ted Kaufman (writercrmp@aol.com), July 26, 2001.

Schneider MTF specs are readily available over the web at Schneideroptics.com. Rodenstock MTF test results are available at butzi.net.

Both the 80mm Rodenstock and the 90mm Schneider are similarly wonderful over the majority of the field, but the Rodenstock drops off to around 35% contrast at the corner at f/8 (at 40 lp/mm), while the Schneider dips to only about 50% at f/5.6 (at 45 lp/mm), which is why I give the nod to Schneider.

A very good book which goes into great detail on enlarging lenses is Ctein's "Post Exposure." Ctein says, "Diffraction takes a toll on sharpness as you stop down. A lens that performs optimally at f/5.6 always beats out one that is optimum at f/11."

Another instance where an f/5.6 optimum is handy is when making big enlargements from generously exposed negatives. 2:00 at f/11 turns into :30 at f/5.6.

-- Brian Hinther (brianh@onewest.net), July 30, 2001.

"A lens that performs optimally at f/5.6 always beats out one that is optimum at f/11"

I you have 2 lenes, the first optimal at f5.6 and the second optimal at f11, and you always use f/11 (say for DOP reasons), is the first lens better (at f/11)?

-- Michael Feldman (mfeldman@qwest.net), July 30, 2001.

Let us assume that a print is done at f11. Ignoring differences that occur at f8 or f5.6, which lens is going to give the best results (including into the corners) - Schneider APO or Rodenstock APO? In case it's relevant, I'm thinking about the lenses in the 100 - 105 mm range.

-- Ed Hurst (BullMoo@hotmail.com), July 31, 2001.