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Post by nikonbob on Jul 10, 2010 13:05:30 GMT -5
I picked up a Ross 3&1/2" F3.5 Definex in Contax mount. On the lens face it says London and coated lenses but on the mount it has made in Scotland and also "STEWARTRY". It does appear coated with a slight purplish cast. The aperture ring is slightly stiff but functions but the lens appears seized on the infinity setting. Any additional info on the lens and how to disassemble it to cure the focus issue would be appreciated. Thanks.
Bob
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PeterW
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Post by PeterW on Jul 10, 2010 16:50:12 GMT -5
Can't help with the disassembly, Bob, but Ross was a well-respected London optical company with roots going back to about 1860
In the late 19th century Carl Zeiss made a number of Ross lenses under licence, and Ross made some Zeiss lenses under licence
The three and a half inch Definex (that's about 89mm focal length) Crops up more often in a Contax mount than in other mounts. The mount was made for Ross by Stewatry in Scotland, a company that specialised in high-precision accessories for cameras such as Leica and Contax as well as lens mounts..
In the 1930s and 1940s the Definex had a good reputation but to my knowledge I've never seen any pictures taken with one.
PeterW
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daveh
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Post by daveh on Jul 10, 2010 17:43:32 GMT -5
I looked the Definex up earlier this evening. The only thing I came up with was that someone quoted it as 91mms! Someone obviously was converting inaccurately: 3.5x25.4 is 89 as near as dammit. Unless it was a different lens.
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Post by nikonbob on Jul 10, 2010 18:24:19 GMT -5
Peter
That pretty well jibes with what I have been able find out. Seems to be well made right down to the mount. From the serial number one site places it as 1946-37 production which seems likely as the lens is marked coated and appears so. I suppose since it is stuck at infinity I could stop the lens well down and try a few shots.
Dave
On the small chrome ring that the F stops are engraved on is also engrave 89mm. I too have seen 91mm referenced and have seen photos of other lens so marked on the same ring. I can only guess that Ross was fussy enough to mark the exact focal length of the lens after it was assembled. Today that plus or minus would likely be considered within manufacturing tolerances and all would be call 90mm. That is just a guess on my part.
Bob
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Post by nikonbob on Jul 11, 2010 9:42:12 GMT -5
Just an update to say that with the help of a propane torch to heat the lens the focusing helical finally started turning. I got it apart, bathed the parts in varsol and relubed it. One small snag left with a tapered spring to sort out and it should be good to go. Fingers crossed, having two left hands to work with.
Bob
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