Double and Triple Protars

[zzjing]

I know almost nothing about LF Photography, and came upon the terms above in the book Gravity's Rainbow. And I would like to know, what exactly do the "Double" and "Triple" mean in those names? Thanks in advance.

[Louis Pacilla]

Welcome to the forum!

The "double" is a lens w/ two different focal lengths in one lens for instance ...Both cells = 7" & one cell = 14"
The "triple" would be three focal lengths in one lens and again...Both cells = 7" one cell 14" the other cell 11" so triple focal lengths in one lens.

[mdarnton]

"Cell" means in this case one half of the lens, on either side of the center. So, you can use either the front, or the back, or the two together, to get the equivalent of three different lenses.

[Dan Fromm]

I just looked in an ancient Zeiss catalog.

Zeiss sold Protar Lenses, a single cell in a barrel, and Double Protars, two cells in a barrel. Double Prodars were offered with equal and unequal cells. Double Protars with equal cells offered two focal lengths; a single cell, the complete lens with both cells. Double Protars with [edit to change equal to unequal]unequal cells offered three focal lengths; one single cell, the other single cell and both together.

Triple Protar doesn't seem to be in Zeiss' vocabulary.

[David Lindquist]

Thank you for this Dan, that's been my understanding. I think you mis-spoke in this sentence: "Double Protars with equal cells offered three focal lengths; one single cell, the other sincle cell and both together." and meant to say "Double Protars with unequal cells offered three focal lengths......"

David

[Dan Fromm]

Thanks, David, I've made the correction.

[zzjing]

Thanks all for replying.

[Jim Galli]

Whether Zeiss and Bausch & Lomb used the "triple" terminology or not, the ones with three distinct possible usable focal lengths became known in photo speak as "triple convertibles" and thus the non cataloged term "triple" Protar. A triple will always be either f7 or f7.7 combined, while a "double" will be f6.3 combined. When used singly, they are usually f12.5. A single cell used alone is a full anastigmat lens.

[Keith Fleming]

Are the lens cells of the Zeiss and Bausch & Lomb Protars interchangeable? For example, if I had a Zeiss Protar with one cell (say a 290 mm) that was unusable, could I find a Bausch & Lomb cell of equivalent focal length that would screw directly into the Zeiss barrel?

Keith

[pjd]

Are the lens cells of the Zeiss and Bausch & Lomb Protars interchangeable? For example, if I had a Zeiss Protar with one cell (say a 290 mm) that was unusable, could I find a Bausch & Lomb cell of equivalent focal length that would screw directly into the Zeiss barrel?

Keith

Not sure if Zeiss and B&L Protar VII cells have the same threads, I'd like to know that too. I do know that Ross and Zeiss Protar VII cells have different threads. I have a Zeiss Protar VII D set in brass barrel and a Ross Protar VII type lens of similar size in an aluminium barrel, but the cells don't interchange.

On the other hand, I have an Ilex Acme No. 4 shutter (home to a Turner Reich 8x10) that also takes the cells from the Zeiss D set Protar VII cells (57mm slip on diameter). Not the information you were looking for, but maybe of interest to someone out there.