Early Ross 6-inch f/4 with iris aperture?

[renes]

I purchased 6-inches Ross petzval lens with an iris aperture f/4 - 6 - 8 - 11 - 16 (contains 20 blades) that was made around 1855 - based on serial no. 4939.

Was an iris known so early or someone has mounted it here later?

I am not also sure what this Roos petzval was aimed for... VM suggest f/4 only for Stereographic Lens, but if the lens was fitted with iris later than the lens was originally faster. Front lens glass is 42mm. Is it possible to recognise it by cells inspection? Hope someone knows the answers.

[Steven Tribe]

I was in correspondence with the lister and mentioned to him that it must have converted (professionally) to an iris system much later the serial number indicates. I'll check the listing again but I seem to remember there being signs of a double conversation. First to Waterhouse stops and then to a full iris. Looks like someone was glad for it's qualities!
I think you are right that it was originally a little faster when it was a Studio Gem/CDV objective. The conversion was done when faster processes were available and for outside use. perhaps?
Have re-read the Ross early Petzval section in VM (I don't think there is more reliable info. elsewhere! - unlike Dallmeyer). Sounds like a small F.3 CdV objective. There may be a "ledge" system inside the hood for use of a front stop!

[renes]

I have checked it again and yes, VM also says about a double conversions from waterhouse stops to a full iris. It looks like the lens was originally about f/3.5 - front lens diameter suggests it (but Ross CdV petzvals were only f/3?). What might also helps in identification is that both lenses (crown too) of the rear element are threaded.

Unfortunetly the hood is lost with my Ross.

[Steven Tribe]

I didn't follow this (320801730184) to the end - what a good price for the buyer!
The difference in front/rear glass diameters is typical of early Petzvals. There are one or two owners of small low number (Rofs) Petzvals here so perhaps they can contribute?
Richard K has an early Ross Petzval (3 digit serial number) and there are photos in the thread "oldest lens" which hasn't been updated recently. His has only two screws mounting the tangential drive plate to the sleeve. And yours has 2 screw holes too, perhaps?

[renes]

I didn't follow this (320801730184) to the end - what a good price for the buyer!
The difference in front/rear glass diameters is typical of early Petzvals. There are one or two owners of small low number (Rofs) Petzvals here so perhaps they can contribute?

It was me, that's my Rofs :)

Rear glass diameter is 45mm, I will fit it to Copal #3 shutter by an adapter which I will order in mechanist. He might also make a new hood. Bought it for a British wooden 1/4 plate that I am going to buy, do not know yet which one to choose but it has to have rather larger lens plate board size to allow to fit Copal 3 shutter.

Hope "Rofs" owners will contribute.

I am out of my home now, but I think there are 4 screw holes.