Not too long ago, I had to clean a rear element on one of my M lenses. Well, looking into the lens, I see some swirl marks around the edges of the element. Don't know if this is from the factory, but I suspect that some of the lens barrel black paint made its way onto my cleaner dampened cloth and perhaps made for a gritty ride on the element! This will be covered, so no worries about being stuck with a clunker lens. Thought I'd pass this precaution on to other M users. I would say if you need to clean that element, maybe use a clean area each time and work towards the edge rather than running it around the edge in a circular motion. That way, the possibility of gritty contaminants is lessened. Maybe the same applies for the front element as well!

-- Fred (yuma@yahoo.com), March 03, 2002

Answers

The standard procedure that is advised in every single lens cleaning instruction that I've seen, is to start in the middle and work outwards. For the rare times that I need to clean a rear element, I just blast it with compressed air, then take a mini LensPen (yes, they actually come in two sizes) and use it as directed. I have yet to damage or smudge a single lens.

-- Anon Terry (anonht@yahoo.com), March 03, 2002.

A surgical strike on the offending grime in this case would have been excellent. I will order one of those lens pens straight away for such occassions, thanks.

-- Fred (yuma@yahoo.com), March 03, 2002.

The swirl marks are residue from an incomplete cleaning. Breath on the lens and clean that off using a clean lint free cloth in a circular motion.

-- John Collier (jbcollier@powersurfr.com), March 03, 2002.

"For the rare times that I need to clean a rear element, I just blast it with compressed air . . ."

If it's eally compressed air, maybe that's OK. The stuff that comes out of the cans we buy in the photo stores isn't air though. It's a pressurized chemical that can:

A. Leave a residue on the lens; or

B. If you're really unlucky, some of the chemical can escape in liquid form, freeze on the glass as it evaporates, and crack it.

If you must use it, then hold the can level to make sure no liquid can run out of the nozzle tube; and keep it 8 or 10 inches from the glass.

-- Bob Fleischman (RFXMAIL@prodigy.net), March 03, 2002.

I'm pretty sure that the swirl marks aren't residue, but I'll try it out thanks. I'll report what happens later on after trying it...

-- Fred (yuma@yahoo.com), March 04, 2002.

Compressed air usually has a little bit of oil and water mixed in with it courtesy of the compressor and the compression process. I work at a company that produces electro-optical products and we use air that has been thru filters to remove the oil & water. If that's not available then tinned air is fine but you have to watch out for condensation.

Cheers,

-- Duane K (dkucheran@creo.com), March 04, 2002.