Berthiot Perigraphe - balsam excess?

[coisasdavida]

Hello all,

I got this lens recently, it is a Berthiot Perigraphe no. 3 serie VI 120mm f/14.
Very short barrel with a wheel stop.
On close inspection I found some yellow transparent substance glued on the inside surface (close to the edges) of both front and rear groups.

http://farm8.staticflickr.com/7290/11343030534_0a8da912aa_b.jpg

I can be seen with the lens assembled and even thru the smallest stop. It is around 1mm wide, all around the edge on both groups, as if it had a purpose.

Should I use benzene to try to remove that? Or should I paint black over it?

[Dan Fromm]

I can't give good advice except to say (a) that neither of my f/14 Perigraphes has anything like that and (b) the one lens I've had that manifested anything like that (with what looks like balsam around the edges of the elements) was a 16/2.5 Luminar that appeared to have been baked and that had visible voids in the balsam between the cemented elements.

Try asking on www.galerie-photo.info

[David A. Goldfarb]

Better not to mess with it, if it involves removing the lenses from the mounts, I'd say, and worrying about alignment problems or possibly cracking the lenses when you put it back together. Take some photographs and see if you have a problem, and if you don't have any obvious problem, then leave it as is.

[Steven Tribe]

I have little clear balsam visible in my Perigraph. This looks like standard slow change in the balsam layer, which will not effect performance yet. These small lenses are more difficult to re-balsam that larger ones. A few makers did rely on a slight excess of balsam to ensure a tight fit in the brass lens cell. This is quite a good idea, as I have seen a lot of turned brass mounts where the lens has now become "floating/rattling" in the glass/metal mount.

[coisasdavida]

Thanks for all answers.
David, I did a few 5x7" negatives to try it out. Didn't like them much (comparing to what I get from a 14cm f/18 Protar, a 155mm Primoplane and a 11cm f/18 Protar).
Maybe the lens is not so good, maybe that line is causing some blurriness.

[David A. Goldfarb]

I use mine on 8x10", and it covers stopped down, and is reasonably sharp for a lens of its era, so I wouldn't suspect a balsam issue around the edges to impinge on the 5x7" image, unless you were using very significant camera movements. It's not a lens to be used wide open--f:32 or f:45 seem to work best for me.

[Steven Tribe]

I have had a look at my perigraphe's construction and I have to say it would not be easy to remove the symmetrical glass elements and do a repair!

[coisasdavida]

Thanks for your answers again.

I have used it at f/56 (smallest stop on this wheel) without any movements.

I agree, this one is not to take apart. My idea was to clean it with solvent, but that would probably lead to other problems as soon as the solvent would sink into the gaps.

I'll take it as it is! And probably learn to like it this way!

[Dan Fromm]

Guilherme, ages ago someone (Georges Laloire?) cautioned me to be very careful when cleaning my Perigraphes. Some were made with blackening at the edges of the glass that's soluble in solvents, including water, often used to clean lenses. Be cautious.

[coisasdavida]

My guess is that someone repainted mine before it got here, I don't know, it looks like it has two different types of black paint applied to it.
I tried acetone before posting here, it removed some black paint, but not all of it, and none of the yellow stuff.

I put it back on the box type DIY camera where it was and I plan to use it like this.