View Full Version : Petzval barrel repair - Light Traps

karl french
12-Jul-2018, 08:52
Just picked up a very reasonably priced Dallmeyer 3B. It's missing the two bands of light trap material on the inside of the outer barrel. Any recommendations for a thin material (velvet? felt?) to replace them with. There isn't much play between in the inner and outer barrels.

Lou Baleur
12-Jul-2018, 21:05
telescope flocking material. they make it in many varieties: self adhesive paper, tape, board, foil.


Steven Tribe
13-Jul-2018, 00:17
I have never seen other materials here than very thin velvet. Actually, I have found that "low quality" velvet ribbons (for wrapping gifts etc.) provide a degree of "compressibility" which the more expensive velvets don't have.

This is not a light trap. It takes up the slight play between the brass sleeve and the barrel and gives more precision to the focussing mechanism.

I thought you were talking about the traditional "finish" inside the barrel, where blackened paper tape was used to secure light tightness around the focussing track and fitted WHS guide!

karl french
13-Jul-2018, 07:33
Thanks all. I used some adhesive backed felt I had on hand. The outer sleeve is now quite snug on the barrel, but that's fine considering the lens is missing the focusing pinion. I may pick up some velvet ribbon. The inside of the barrel is in pretty good shape, though there are light scratches on the rear surface of the front group. Sort of a strange place for them.

Nicely enough the lens came with its hood and flange. Likely because the flange is stuck onto the barrel and the hood is slightly cross threaded, so quite hard to remove. Still, I'm pleased to have this user 3B No. 45948. I'm curious to see how it compares with the Bausch & Lomb copy I have.