How to open a voigtlander petzval lens front group

[quencyku]

there are two finger print inside the first group. but I can't find a way to disassembly them. For help.

[goamules]

The front group is two lenses, cemented. But I assume you mean ON the glass, not IN it. They unscrew, take the hood off first, then unscrew the remaining pieces. If they are stuck, just carefully reach inside the barrel from the rear, if you can get that end off.

[quencyku]

[quencyku]

[quencyku]

[quencyku]

please show me which part can be unscrewed out ?

[Steven Tribe]

This is a Newton ring, where reflected light is dispersed into light's colour components because there is a slight air space between the cement or balsam where the cement has "lost it's grip" on the glass surface in the "rainbow" area.

As it is, it won't effect optical performance.
Replacement of the balsam is not difficult once you have opened up the front lens cell.
I have never worked on an early Voigtlander. I suggest you wait for someone who has!

I don't think the inside edge has been turned down in lathe - it looks too robust. There must be a screw in system, probably the inside rim where it disappears into the wider section of the cell.

My guess is that the balsam has been replaced by a previous owner/user with synthetic cement which often has this kind of partial breakdown.

[quencyku]

So, it is a petzval? lens No. 20267
the total length of the lens with hood is 8 1/4 inch. the diameter of the front elements is 3 1/4 inch ,rear 3 1/4inch, the distance of the front and rear elements is 5 1/2 inch. what is its model?

[Steven Tribe]

I assume it is a Petzval because it has the r&p drive and a brass sleeve. Voigtlander had just begun to make early Euryskops around this serial number.
You find out by checking:-

- are the front and rear cells identical (focal length)? If so, a Euryskop.
- is the Waterhouse slot midway between the two lenses? If so, a Euryskop.
- is there a number engraved at the top edge of the barrel? Is so, likely Euryskop.

A Petzval of this size wold cover in the range 5x7" or plate size and have a focal length of around 10", if it is the usual "quick acting" F3.2 version.

[quencyku]

The focus length is about 10 inch; the slot is in the midway of two lens; No number engraved in the top edge;the size of two lens is 3 1/2 inch