View Full Version : 5x7 protar lens

Lukas Werth
30-Oct-2005, 13:08
Hi, I recently got a Bausch & Lomb 5x7 protar lens and tried it on my 8x10 at infinity. I couldn't bring it to cover, although the catalogue http://www.cameraeccentric.com/html/info/bauschcatb/p29.html
says it does (at small stops). Am I missing something?

Michael Kadillak
30-Oct-2005, 15:48
I have found that format coverage needs to be qualified by both the author and the reader.

My point is that if a lens bearly covers 8x10 at f64 at infinity with zero movements, why would I want to bring this lens into the field? Any buyer of a lens should know from a reputable source how many centimeters or inches at say f22 the lens provides over the fomat you want it to cover.

Are you sure that it was touted to cover 8x10 as a single cell? If so the quality of the image could be suspect to abberations, but still usable for contact printing

I would be particularly suspect of excess coverage because it is listed as a 5x7 protar.


30-Oct-2005, 20:28
My 5x7 Protar V f18 covers 8x10 stopped down all the way. These Protar V's have really big coverage. My 10x12 covers 12x20 stopped down. I don't know why yours does not cover if it is a V series.

Ole Tjugen
31-Oct-2005, 03:00
Which Protar is it? V, IV, VII and VIIa are all different.

Lukas Werth
31-Oct-2005, 03:07
My initial question was perhaps a bit short: yes, my lens is a Protar Series V, f18. The original Bausch & Lomb catalogue (to be inspected at the website menioned above) states it should cover 8x10 "at small stops". Michael, as for the single cell: it is no convertible protar.
Why using such a lens? Well, I just like wideangles, and I also use the 4x10 format which it covers in any case, even with some movement.

Michael Kadillak
31-Oct-2005, 18:40
Am is simply missing something here. If the lens covers 4x10 with movements as you stated, (emphasis on the "10" dimension) -why then could it be delinquent on 8x10?

Dan Fromm
1-Nov-2005, 04:59
sqrt(4^2 + 10^2) = 10.8

sqrt(8^10 + 10^2) = 12.8

Michael, 8x10 needs 2" more coverage than 4x10

Michael Kadillak
1-Nov-2005, 06:31
Thanks Dan.

Dan Fromm
1-Nov-2005, 06:48
Oh, my, what a stupid typo. That should be sqrt(8^2 + 10^2).