Ross 16" Apo Process Xpress info

[Iga]

Hi all !
I'm looking for information about f10 / 16" Ross Process Xpress lens. I found some data of other focals, but nothing about 16". If anybody knows something - please, let me know.
Thanks in advance,
Igor.

[Martin Courtenay-Blake]

The info I have on the Ross process lenses covers the whole group - 9.5in. to 48in. Aperture is listed as f10 - f12.5 and field coverage 34 - 37 degrees. They are symetrical 6 element 4 group lenses with the inner of lenses air spaced and the outer pair on each side cemented. Construction very similar to the Dagor but with the additional 2 air/glass surfaces.

Cheers

Martin

[Iga]

Thanks a lot Martin !
Do you know 16" coverage or image circle ?
Thanks,
Igor.

The info I have on the Ross process lenses covers the whole group - 9.5in. to 48in. Aperture is listed as f10 - f12.5 and field coverage 34 - 37 degrees. They are symetrical 6 element 4 group lenses with the inner of lenses air spaced and the outer pair on each side cemented. Construction very similar to the Dagor but with the additional 2 air/glass surfaces.

Cheers

Martin

[Dan Fromm]

Igor, didn't you take trigonometry in secondary school? Or perhaps, if you're young, primary?

250 mm +/-.

Martin, the design type you described is usually called a plasmat.

Cheers,

Dan

[Iga]

You learned these manners in high school, Dan ?
In any case, thanks for your calculations.
Igor.

Igor, didn't you take trigonometry in secondary school? Or perhaps, if you're young, primary?

250 mm +/-.

Martin, the design type you described is usually called a plasmat.

Cheers,

Dan

[Dan Fromm]

Grade school, Igor, grade school.

[IanG]

A Ross advert says the 16" f10 Process Xpres covers 15"x12" so something up with those calculations.

The image circle should be more than 19" / 350mm

Ian

[Iga]

Thanks, Ian. I've found the same data at Camera Eccentric site, but it says "covers 15x12" at full aperture copying same size", ie closeup work..
Igor.

A Ross advert says the 16" f10 Process Xpres covers 15"x12" so something up with those calculations.

The image circle should be more than 19" / 350mm

Ian

[Martin Courtenay-Blake]

Thanks Dan....I did wonder if that formula had a real name. Does plasmat cover all 6/4 symetricals or just those such as these Ross lenses (as well as the similar Symars, G-Clarons, Sironars etc.) with the un-cemented elements on the inside?

Cheers
Martin

[Dan Fromm]

Martin, naturally it is confusing. There are, very (much too?) broadly, two ways to arrange a 6/4 symmetrical lens. Each cell with meniscus outside, cemented pair inside; each cell with cemented pair outside, meniscus inside. The first type is usually called a 6/4 double Gauss type, e.g., the original sechslinser Planar of CZJ, the TTH OPIC and descendants, the Xenar, ... The second type is usually called a plasmat, includes the original Meyer Plasmat (according to the VM a Rudolph design), our plasmat type Symmars (remember, the trade name was first applied to a 6/2 dagor type), Sironars, G-Clarons (same comment as for Symmars), ...

But if you look in Brandt, you'll see that he calls the original Planar and its offspring type I double Gauss and the original Plasmat and its offspring type II double Gauss. I guess that the jargon people use when talking about lenses varies with the language they speak.

Cheers,

Dan