I was out looking at 35mm lenses this weekend and noticed the 35mm Summicron ASPH is somewhat longer than the version prior to the aspherical lens. Why is this so? Could it be that the aspherical element (s) account for this increase in length? Which element or elements are aspherical? Just curious. Thank you experts.

-- John Alfred Tropiano (jat18@psu.edu), November 11, 2001

Answers

Go to this link: http://www.leica-camera.com/produkte/msystem/objektive/pdf/index_e.html and download the Adobe file for this lens. And a terrific lens it is, I might add.......

-- john costo (mahler@lvcm.com), November 11, 2001.

John Alfred: Yes, sort of.....

Every Leica-M lens from 35mm to 75mm, prior to the ASPH designs (and excepting the 50 f/2.8), uses a variation of the same optical formula - the 'double-gauss'. If you go to this web site you can see all the optical diagrams from 1954 on. The 'double-gauss' is everywhere - a more or less symmetrical design with 3 to 4 elements each side of the aperture. In cross-section it looks like 6 to 8 nested peanut shapes.

When Leica created the first ASPHERIC 35 f/1.4 in about 1990, they decided that they had reached the limits of the double-gauss layout - the design was compact and elegant, but just couldn't be stretched any further to deliver better quality than they already had, even with aspherics and better glass and so on.

Instead they started from a 'blank computer screen' and designed a whole new lens formula from scratch, using aspherics, but also a lot of other optical ideas, including the concave front and rear elements. This new layout, or at least the new principles behind it, has been picked up and modified to create the 35 Summicron-ASPH you saw, and also the 28 Summicron-ASPH.

It is the combination of ALL the new lens design ideas, and not just the ASPH surface, that make the 35 f/2 larger and more heavy. For example, the rear element is very thick - almost as thick as the whole rear half of the previous 35 'cron - which adds both length and weight.

For your last question: the aspherical surface is the first surface BEHIND the aperture blades. (I think)

(P.S. the web site linked above also shows the optical diagrams of the screw-mount lenses, too. Links are at the bottom of the 35mm page I linked to.)

-- Andy Piper (apidens@denver.infi.net), November 11, 2001.

Well, Andy, that's quite a website. It answers questions that have been posted here for a couple of years, like what the formula of the 40mm Summicron looks like. I wonder how the authors of the site aquired such a wealth of data. I saved it all on a floppy for later reference.

-- Bob Fleischman (RFXMAIL@prodigy.net), November 12, 2001.

Bob - did you notice they even have the design for the never-produced 40 Elmar(it) f/2.8 - a tessar layout.

I think it's part of the site for a Korean camera store.

-- Andy Piper (apidens@denver.infi.net), November 12, 2001.

Optical layouts are in Puts' book too.

-- Robin Smith (smith_robin@hotmail.com), November 13, 2001.

When the 35 ASPH Summicron-M came out, I called Jim Kuehl to buy one. He talked me into buying a new pre-ASPH. Did I make a mistake?

Actually, Don Chatterton also recommended the pre-ASPH. I'm still trying to decide if they just wanted to get rid of a discontinued lens or actually believed what they were telling me.

As for the pre-ASPH, I love the neutral color rendition and the 35 is a focal length I almost never use wide open (my people lenses are medium telephotos).

-- Bud (budcook@attglobal.net), November 13, 2001.

Andy,

the 40/2.8 was indeed produced at least in a few examples: I run across an ebay auction where someone was selling one about 5 months ago. It might be that these were just prototypes ...

Kai

-- Kai Blanke (kai.blanke@iname.com), November 13, 2001.

When the 35 ASPH Summicron-M came out, I called Jim Kuehl to buy one. He talked me into buying a new pre-ASPH. Did I make a mistake?

I don't think so. The ASPH is meant to be better into the corners than the preASPH at f2-f4, but many people like the bokeh of the earlier lens. The earlier lens is smaller. God knows which is "better". They are both very good by anyone's standards. They seem to be roughly equally valued in the second hand market.

-- Robin Smith (smith_robin@hotmail.com), November 13, 2001.

I haven't bought the ASPH because I already have the 8 element 'Cron, plus the Lux. I couldn't bear to part with either. If I had a third 35mm, I don't know how I would decide which one to take a picture with.

For now, I've decided that if I'm happy with something, it doesn't need to be replaced just because there's something better out there.

-- Bob Fleischman (RFXMAIL@prodigy.net), November 13, 2001.

Right-on Bob! That's the whole point of not babying your Leica gear. You need to wear it out so that you can replace it with that "better" unit someday ;-)

-- dan Brown (brpatent@swbell.net), November 13, 2001.

"When the 35 ASPH Summicron-M came out, I called Jim Kuehl to buy one. He talked me into buying a new pre-ASPH. Did I make a mistake?"

.

. . I don't think so. SHE doesn't think so. The puppy says the jury is still out, but what does HE know?

35 pre-ASPH, FP4, 1/1000 @ f/5.6-8

-- Andy Piper (apidens@denver.infi.net), November 13, 2001.

Wow! The sharpness of that photo is the best argument against buying the latest and more expensive version of a fine older lens.

-- Peter B. Goldstein (peter.goldstein@us.cgeyc.com), November 19, 2001.

.....based on a low res 5x7 scan of a high contrast scene probably shot at f/8?!?

-- ray tai (razerx@netvigator.com), November 19, 2001.