APO Summicron-M 90mm ASPH and Filters

greenspun.com : LUSENET : Leica Photography : One Thread

Greetings,

I recently purchased an APO 90mm f/2 ASPH and the instructions booklet contained a loose leaf adenndum saying

"Caution!

When a polarizing filter is to be used, special care must be taken to ensure that the distance from the back surface of the filter glass to the plane circumscribed by the back rim of the threaded filter mount is at least 1.8mm (5/64"). Circular polarizing filter E 55 Order No. 13335 must not be used on this lens."

Sure enough, the front element of the lens is visibly quite close to the innermost filter thread, so I'm guessing the problem is the filter could scratch the front element.

First, why would this warning only apply to polarizers?

And does anyone have a brand of polarizer to recommend for this lens? The local photo store is reluctant (understandably I guess) to let me open the seals on their better filter packages so I can measure same. (I know some Leica fans would recommend no filter period, but I've learned a polarizer sometimes really helps, especially down thisaway in sunny Florida.) Any suggestions/advice are greatly appreciated.

Cheers, Jeff

-- Jeff Stuart (jstuart1@tampabay.rr.com), July 05, 2001

Answers

The simplest solution would be to remove the glass from a scratched- up 55mm filter and use the mount as a spacer bewteen the lens and polarizer. It is unlikely that there will be vignetting with a 90mm lens, but a test shot or two at the end of a roll will make certain.

-- Jay (infinitydt@aol.com), July 05, 2001.

My Heliopan polarising filter works just fine.

Cheers,

-- John Collier (jbcollier@powersurfr.com), July 05, 2001.


Heliopan filters have a bit thicker rim than other filters I own. This has been a disadvantage for very wide angle lenses, but could make it the right choice for that 90mm with a front element clearance problem. They also probably make the best polarizers in the world, and all are calibrated so they are not too hard to use on a rangefinder.

-- Andrew Schank (aschank@flash.net), July 05, 2001.

Anyone who has the Universal Polarizer and wants to use it on an E55 90 Summicron (APO or non-APO)here's how to make an adaptor, the parts cost about $15:

Ingredients: 1 55-52 step-down ring 1 empty 52mm filter ring (from filter with glass removed--careful not to get cut!) 1 52mm Cokin adaptor for the "A" series 1 tube Red Loctite

Tools: Bench grinder/polisher or Dreml Tool set

Procedure: 1. Grind flange of Cokin adaptor down to 56mm diameter (careful, it gets *really hot* when you grind on it) 2. Use rubber impregnated Dreml polishing wheel to smooth the ground surface (or use very fine automotive sandpaper) 3. Put small amount of Loctite on male threads of Cokin adaptor and screw into front of the empty 52mm filter ring. 4. Put small amount of Loctite on male threads of empty 52mm filter ring (now with Cokin adaptor permanently attached) and screw into front of the 55-52 step-down adaptor.

To anticipate the question, no a 55mm Cokin adaptor alone won't do the trick, nor an empty 55mm filter plus the Cokin adaptor. It needs the 52mm ring's thickness *and* exact diameter to clear the retaining tabs on the Universal Polarizer.

-- Jay (infinitydt@aol.com), July 05, 2001.


Greetings again,

Thanks for the suggestions, I appreciate your help. I think I'll check out the Heliopan (what a great name.)

Thanks again, Jeff

-- Jeff Stuart (jstuart1@tampabay.rr.com), July 06, 2001.



Moderation questions? read the FAQ