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

[Martin Courtenay-Blake]

Once again thanks Dan. Hopefully now I'll understand what some of you more learned folk are talking about.

I haven't been able to obtain a copy of Kingslake too date and I really should get hold of a copy of the VM. I did, however, find a copy of Arthur Cox's tome on Photographic Optics which is a good intro into lens design and has a great collection of cross sectional diagrams and data tables but it is somewhat biased towards smaller formats and cine (he did work for both TTH and more latterly Bell and Howell)

Cheers

Martin