This lens is known for itīs weak 3.4 diafragm, with halos from ligth sources when wideopen and low contrast. I have read some improvement done by blackening the two inner tunnels on each side of itīs symetrical construction. Has any one read about it?, and if so; what have you found by doing it?

-- R Watson (al1231234@hotmail.com), May 08, 2001

Answers

Roberto, someone has a website about this. He said to take the lens apart and blacken the edges of one or more elements.

However, he also advises filing away part of the protective shield over the rear element, to make it more useable with M6 metering. That sounds like bad advice to me, which reduces my confidence in him. Nevertheless, if I can find my way back to that web page, I'll post a link for you.

Regards,

-- Bob Fleischman (RFXMAIL@prodigy.net), May 08, 2001.

The page has gone to 404 heaven. On it the author recomended blackening the edges of the last element or two.

Cheers,

-- John Collier (jbcollier@home.com), May 09, 2001.

Thankīs for the info, I knew there was something about that some where, Iīll may try to see how the lens looks unscrewed.

-- R Watson (al1231234@hotmail.com), May 09, 2001.

I don't remember anymore the exact optical construction of the 21 3.4 nor the way the rear group is assembled mechanically, but with a lens particularly of that age and a Schneider lens I would be *very* cautions about taking it apart. If you accidentally get separation in a cemented group, or even fail to reassemble everything and tighten to exactly the same specs it was originally collimated at, you are likely to cause a lot more problems than the ones you're trying to fix, which I can't say I have ever noticed with my S/As, although the black one from 1977 (which I still own and use) always seemed a bit contrastier than the 1963 chrome version I kept until recently. The 21 3.4 is fully usable wide open, it just vignettes more than the 21 ASPH. Both lenses are better at 5.6 than wide open.

-- Jay (infinitydt@aol.com), May 09, 2001.

I agree with Jay in that it is a job best left to a professional. My 21/3.4 was very susceptable to flare wide open. I tend to photograph in dim backlit situations more often than not so this was very annoying. The 21/3.4 is good at f/4, much better than the 21/4 at f/4 but the 21/2.8Asph is a stunning lens even wide open. Perhaps the new Voigtlander/Cosina 21 will be a good low cost alternative.

Cheers,

Cheers,

-- John Collier (jbcollier@home.com), May 09, 2001.

OK; thankīs for the advices, I was temptde and unscrew it, it was very easy to figure out, now I better think whatīs next. Iīll explain what I did, whit my fingers unscrew the rear side of the lens, and the entire group of elements came together, it was so easy and made me realise where the problem may be, there is betwen the center elements (those near the diaphragm), and the larger ones, a round tunnel of ligth, the fact is present on the two sides of this lens construction, remember it is a simetrical design, so what we have in front we have in the back, to unscrew the front group I needed a compas, better do it carefuly. Well now Iīm here, what Iīm thinking is, not paint but cover with black silicon those two tunnels, why silicon? because is easy to remove.What Iīm speacting to get with it?; Well if you work with the lens wide open there is a chance that the ligth that goes through the tunnels contaminates the space in betwen front and rear group, just where the diafragm goes, by looking at it seems logical.Iīll let you know my results.

-- R Watson (al1231234@hotmail.com), May 09, 2001.

DO NOT USE BLACK SILICONE!!!!!

It gives off corrosive fumes as it dries which will attack the coatings, adhesives and lube in your lens. If you do not believe me put some on your finger and take a good sniff. You can taste the acidity. This off-gassing lasts a long time. Also any lube in your lens wil tend to cause black silicon to break down into an gooey mess.

DO NOT USE BLACK SILICONE!!!!!

Again if you do not know what you are doing, let someone who has done it before do the modification.

Not so cheerily,

-- John Collier (jbcollier@home.com), May 09, 2001.

Thankīs John, I removed it, already dry, it didnīt touch any glass surface, hope this doesnīt have any consecuences, man you scared me, well I closed the lens back, now I know how it feels to atempt doing something on a leica, enough for now.What I also did was taking and before and after picture wide open against a ligth source.Weīll see.

-- R Watson (al1231234@hotmail.com), May 10, 2001.

I knew I had it somewhere; this is the address where I read of this SA 3.4 improvement;

http://reality.sgi/jessen_esd/angulon_compare.html

For who ever cares.

-- R Watson (al1231234@hotmail.com), May 23, 2001.