[LargeFormat] Ross lens, Epsilon shutter

[Clive Warren]

At 8:00 am +0100 21/4/02, philip.lambert wrote:
snip
>supplied German needs at the time?) The 5" WA Xpres probably replaced
>imported  LF lenses like Xenar and Ektar. Wray also made LF lenses for
>British MPP then. (avoid their 89mm).  I should guess it had an extra
>element for the added corrections needed to allow f4.5 on a widefield lens
>unless you were expected to stop down a lot. The Epsilon shutter was said to
>be unreliable but mine never played up. Does it have a standard coax socket?
>Some had a non-standard socket.  Philip
snip

Philip,

The Xenar would not have had the coverage nor corrections required 
for aerial photography. The Aero Ektar lenses came along much later 
and were used by the UK for aerial surveys during WWII, probably 
supplied under the "Lease Lend" scheme and came over on Liberty ships 
in the early days. Michael Briggs probably knows  a lot more about 
the history.

In my post I was referring to two main types of lens, the standard 
Xpres and the WA Xpres. These are very different in design and 
intended purpose.

The standard Tessar type design of Xpres lens includes an additional 
element in the rear cell probably to avoid infringing the patents on 
the Tessar design rather than adding huge amounts to the performance 
of the lens.

The WA Xpres is a different design - ie a Plasmat rather than a 
Tessar. The Plasmat is a superior design in terms of correction of 
aberrations across the whole field of coverage and the WA Xpres was 
designed to be used for aerial photography where such accuracy was 
important for survey purposes.

The standard Xpres lenses have a great reputation and I am looking 
forward to trying mine out - it is a brass 13" APO Process Xpress f9 
so is compact and may make a good field lens on the 8x10.

Cheers,
        Clive