Ross London 12in xpres f/5.6 (e.m.i) Lens

[Photosinphotos]

Howdy do,

I have come across this rather unusual and seemingly uncommon lens - I think that it is an old aircraft lens but I can't find any information about it. Any ideas? It measures about 5 x 5inch and weights roughly 3kgs

Many thanks in advance

 

[jcdeboever]

That looks to be a large format lens. 304mm. It appears on Ebay as a Royal Airforce surveillance lens. Apparently rare and high quality. The link shows a f/4.5. If your selling it or need info, you may want to contact the person in the link . Yours looks to be in excellent condition.

Ross London 12 Inch F.4.5 Xpres Lens Possibly Air Ministry 304mm In • £175.00

 

[compur]

http://lens-club.ru/public/files/pdfs/3f45d8f6ce12d520e02586f963213c5b.pdf

 

[jcdeboever]

http://lens-club.ru/public/files/pdfs/3f45d8f6ce12d520e02586f963213c5b.pdf

Nice, I knew if anyone, it would be you.

 

[IanG]

This isn't the usual 12" f4.5 Xpres, it's the f5.6 E.M.I version, that means Extra Marginal Illumination, it's designed and optimised to be used at Infinity and have better edge sharpness, Ross didn't recommend it for closer distance. Usually they have an MOD number (Ministry of Defence).

The front element has quite a curve, presumable the rear as well, this is to help even out the edge illumination. As you can see from the images above the normal Xpres has a far flatter front element. This FL isn't listed at that aperture.

Ian