Format / Size Numbers Used on Vintage lenses

[Len Middleton]

Just acquired a vintage Ross No.3 Universal that from its serial number (ca. 1875 to 1880) looks to be from the J.Stuart era, and trying to better determine its focal length, coverage, and maximum aperture. I did purchase the Lens Vade Mecum from Dan to help, but still some gaps in my understanding.

Like my Voigtlander Euroscop "1", trying to make sense of the numbering systems used and whether there is much, if any consistency comparability between manufacturers on format, as I have seen similar numbering used on Wollensak lenses, except they use Roman numerals for the values.

If not consistent, does someone have a chart of No.'s used by the different lens manufacturers?

[ic-racer]

Just acquired a vintage Ross No.3 Universal that from its serial number (ca. 1875 to 1880) looks to be from the J.Stuart era, and trying to better determine its focal length, coverage, and maximum aperture. I did purchase the Lens Vade Mecum from Dan to help, but still some gaps in my understanding.

Like my Voigtlander Euroscop "1", trying to make sense of the numbering systems used and whether there is much, if any consistency comparability between manufacturers on format, as I have seen similar numbering used on Wollensak lenses, except they use Roman numerals for the values.

If not consistent, does someone have a chart of No.'s used by the different lens manufacturers?

Some info here. http://piercevaubel.com/cam/acc/lensanthonyeaviewvar4.htm
I have the "2" and it gives a pleasent soft-edged circle on 8x10.

[Steven Tribe]

There are gaps in everyone's understanding!

There are no logical rules. Generally, increasing values mean increased efls and coverage. Exceptions exist, especialy in France. The l'Eidoscope size 0 is a huge lens whilst 5 is tiny!

The makers had their problems as different formats became popular in the lifetime of a lens' production. So size 0,00 and 000 often appear. Intermediate sizes also appear called "a" in the UK and "bis" in Germany. I have a Dallmeyer meniscus landscape called 5a which has the body of a 5 but the focal length of size 6!
There were periods when German lenses often had size 1 for 9x12, 2 for 10x15, 3 for 13x18 and 4 for 18x24cm (approx.)
The Ross Universal numbering is a special problem as I believe there were 2 different series!
My Universal no.1 covers whole plate (serial number 31661).

[Len Middleton]

Steven,

Sorry for the misunderstanding, but in saying there were some gaps in my understanding, I guess I understated the situation and did not fully reveal how many and how big those gaps actually are... :D

After focusing at infinity and measuring the bellows extension and then the full bellows the Deardorff would allow (approx. 31"), my Ross Universal #3 looks based upon the lens VM to be the 16.5" focal length and f6.0 with coverage for 15x12".

Maybe that information will be helpful to someone else,

Len

[Steven Tribe]

Yes, nice to know for people like me who have a 15x12" camera!