Ross HOMO

[Darrin]

Sorry everyone yet another question from me, plenty more to come as well as I go along. I have this Ross HOMO lens that I have recently restored from a seized diaphragm, just need to replace the iris blades now and the outer barrel. Question is I know nothing about this lens and apparently neither does the interweb, type in Ross HOMO and you get a million pages on the sexual orientation of a Friends actor!
There was one item I saw claiming it is a Ross Homocentric lens...I don't think so. The lens certainly has four groups, a single rear element, possibly a cemented doublet either side of the iris (due to the size) and a single front element, it is coated with an aperture range to f64 and I am assuming its a quality process lens.
Any information most welcome.

 

[~RJ]

"There was one item I saw claiming it is a Ross Homocentric lens...I don't think so. The lens certainly has four groups, a single rear element, possibly a cemented doublet either side of the iris (due to the size) and a single front element, it is coated with an aperture range to f64 and I am assuming its a quality process lens."

The cemented doublet and split rear group conforms with the focal length range for the Ross homocentric lenses. They are moderate lenses with decent coverage equivalent to their focal lengths- yours is rather short at 10inch (sufficient for 5x4). The 16inch version covers whole plate format with movements.

The Vademecum will offer more clarity than Google which corrupts historic language and referents.

 

[Ian Grant]

The Vague Mecum says the HOMO may be an abbreviation for Homocentric.

Ian

 

[~RJ]

The Vademecum offers more clarity than any of us possess and cautiously use "maybe" in the absence of data on the patenting of the lens.

Ross never patented Darrin's lens: - 'homo' is homonymous and the later Google anachronistic faults cannot fathom that this came later, as the Homocentric Patent, from the homogenous symmetrical layout of its predecessor - the Ross Symmetrical lens and then the Rapid Symmetrical lens followed by the Extra Rapid Symmetrical lens: same characteristcs as Darrin describes in the optical layout and aperture. Here is a 16 inch version

 

[~RJ]

You can see it's evolution from the earlier Ross Rapid Symmetrical, optically constituted by two achromatic doublets, obviously symmetrical in group lay out, in its more aged brass - a contrast to the higher grade brass mount of the Ross Homocentric lens:

 

[Darrin]

Thanks for all the feedback everyone. Here is the lens fully restored and back to be being functional. It has a beautiful 16 blade iris which has no click stop or detents so relies on being damped. The barrel seems odd to me though, it has modern styling with an engraved metric focal length of 254mm whereas the lens mount is engraved in imperial inches.
To be more precise in the description of the lens, it is single coated and symmetrical either side of the iris starting with a plano convex element followed by a thick strongly positive meniscus. I assumed this to be a doublet at first due to its thickness, however on close inspection I could very well be wrong, see my photographs below. If that is the case this lens would conform to the f6.3 Homocentric design, could this be an old lens in newish barrel and somehow coated? Why bother?
I have found an advert in Popular Photography in 1951 listing a 20" f4.5 Ross HOMO for $69.50, this would make it an unsymmetrical version introduced in 1912, so perhaps HOMO is an abbreviation for Homocentric...