View Full Version : Corroded early Ross Xpres 7 1/4 f/4.5

13-Jul-2018, 05:57

I recently became the proud owner of a lens which is more than four times my age, a 1918 Ross xpres 7 1/4inch f/4.5. I expected that it might not have been in the best condition, from the photos on the 'bay, but I thought that a quick scrub would brighten it up. However, it seems that there is some significant corrosion to the brass, which affects the lens both cosmetically and also prevents it from being fully dissasembled.

I was able to remove the rear cemented group. Judging by the serial number (and so the age) I believe it should be the triplet version, however, I'm not sure about that. Cleaning the group proved difficult, there is a slight mistiness to the back surface of the lens. I've tired dish soap, isopropyl alcohol, and lens cleaning solution, which have all helped a little, but not removed the cloudiness. I wanted, also, to clean between the front two lenses, but I was unable to remove them from the housing. There is a small screw which was difficult (but possible) to turn, and did not come out. It seemed to have no effect, I thought that it might have been to keep the aperture in place, or else secure the some other part of the lens. I used my lens spanner on the front holes of the lens, which I thought should release the front lens. I was unable to release it, and scratched the front quite badly.

The internet suggests using vinegar and salt on corroded brass and scrubbing hard at it. But I'd only want to do something like that if I could remove all of the lens elements from the body. Does anyone have any tips for unlocking stuck brass threads? Do you think the small screw has anything to do with it? Should I just deal with it? I'd like to fully restore the lens, and repaint it, but I think that is outside of my ability, I didn't make much of an improvement by cleaning it alone. I also found some chips in the front element, and a flat area. I'm not sure what caused it, but I hope it wouldn't effect image quality too much.

I'm not sure what I should do with the lens. I believe the lens covers 1/4 plate and I have a 5x4 camera, so I might try using it on that. I also like the idea of trying to mount in for my DSLR, as its lack of a shutter wouldn't matter. I haven't found anyone posting example images from it, lots of people have said that the xpres lenses are excellent, and that the five element triplet is better than the later tessar style, but I don't really have any context for that. I expect that it would be resonably poorly corrected for colour, and might be optimised for the blue/near-UV because of the sensitivity of the plates used at the turn of the last century.


Thanks for your time.

16-Jul-2018, 13:34
Hi Josh,

The effort for the used condition and chipping of the front element is quite special. Mine is rather ordinary - a 6 3/4inch f4.5 version which I use covers 5x4" format without difficulty, although I have a 7 1/2 inch f4.5 like yours, albeit a later generation (4 element). Yours should cover 5x4" format comfortably at f22. It behaves like a standard lens although wide open it throws open many possibilities. Its coverage is rather limited at this format unfortunately.

Hope you succeed in working those threaded screws out. If you do, it's probably easier to re-plate the carcass - maybe even easier to find another lens in better condition :)

Kind regards

17-Jul-2018, 03:47
Thanks for your advice RJ. I know it isn't very valuable, so I probably shouldn't spend a huge amount of time or money on restoring it, but for some reason I like it. I if I can't clean the front elements I might just mount it on a board and see if I can take some usable image on it.

18-Jul-2018, 14:28
They were very popular lenses here in England at the turn of the century Josh. The factory, based in Clapham, London, had a few generations of these lenses and a significant pre-war and inter-war production of Air Ministry lenses too.

I've found corrosion mostly from imaging near sea salt carrying wind where the humidity is high. One of the UK companies offers home electroplating tool kits which don't require complete submersion - an alternative way of refinishing the lens if painting isn't desirable: http://www.gaterosplating.co.uk/

although the pitting underneath the corrosion might make the lens more period character and correct as it is.

I've yet to discover a lens than doesn't produce a usable image - even a pin hole does that :)

Kind regards,