Restoring a Vintage Lens

As well as the usual souvenirs and peppermint rock, a recent trip to the seaside yielded something much more worthwhile. While frittering away the dog-end of the afternoon browsing in a back-street junk shop, I came across a battered old brass lens.

Here it is, screwed onto a home-made lens board. I did it so my students could use it to experiment with paper negatives in a 5"x4" camera. I thought it might be from an old projector or magic lantern, given that it had a fixed aperture, no shutter mechanism and was focused by a rack-and-pinion. The only thing that made me doubt this assumption was that it had a lens hood (removed in the above photo) – not something you would expect on a lens where the light comes out of the lens, rather than going in.

The main problem with the lens was that the focusing spindle was badly bent so that the pinion teeth didn't properly mate with the teeth on the rack, which meant that it couldn't be reliably focused. Given it was in such poor condition and had cost me next to nothing, it seemed like it might be fun to try and get it back into better order.

Needless to say, the lens came apart pretty easily. A lens like this is a classic example of form and function co-existing in simple harmony, the function of each part being evident by its appearance. There are only six screws in all, four holding the pinion against the rack with two more keeping the rack in place. Other than that, the individual components go together by screwing one into another.

The first task was to clean off the accumulated grime and corrosion. While serious collectors have strong views on what should or shouldn't be done, my interest is in the lens's functionality rather than its collect-ability. Vinegar seemed to do a good job of tackling corrosion, while regular paint stripper brought off dirty and discoloured lacquer.

The most interesting discovery at this point, which ultimately led me to identifying the lens's provenance, was finding some crudely stamped letters on the inside of the lens hood.

Before cleaning, the corroded interior of the lens hood was coated with remnants of  black paint, but when this was cleared away the roughly-stamped word DARLOT and the number 12 were revealed. I suspect that originally, they would have been hidden by a felt or velvet lining and were not intended to be seen. The only other clues I had to go on were the letters AG and number 6680 engraved on the lens barrel.

As the word Darlot meant nothing to me, I thought it might be worth doing a web search. I'm glad I did; it set me off on a hyperlinked journey from which I learned an enormous amount about lens history and design.

The first thing I discovered, showing my ignorance, was that Alphonse Darlot of Paris was a major maker of photographic lenses in the second half of the nineteenth century.

This pdf of a lens catalogue from 1890 shows a range of Darlot lenses.

 Interestingly, the catalogue warns that, "there are many spurious Darlot lenses and worthless imitations in the market". Certainly, my lens lacks the usual ornate engraving and is somewhat flimsy compared to other old lenses I've handled. Anyway, to cut a long story short, my web searches soon revealed that the letters AG might refer to Alexis Gaudin, a Parisian lens maker who had a London shop in the 1850s-60s.

This was confirmed later when I dismantled the rear lens element to clean the inside faces. Written around the thick rim of one glass was a pencilled inscription, Gaudin et Frère 1855 Paris (word illegible) No. 1

Discoveries like this are always quite exciting. To find something as fragile as pencil marks still surviving after being hidden for almost 160 years is like unexpectedly opening a time capsule. I felt like Thoreau when he wrote of finding an arrowhead, "I come closer to the maker of it than if I found his bones. His bones would not prove any wit that wielded them, such as this work of his bones does."

Having dismantled the lens, and before reassembling it, I decided to measure the individual parts and make a scale drawing.

The line drawing was made at twice actual size, comfortably fitting on an A3 sheet of paper. It was then scanned, cleaned up, coloured and annotated in Photoshop.

Technical specifications of the lens, such as focal length, were determined through experimentation. I intend to write about this in a future post. Going back to my original thoughts about it being a projector lens, I now realise that the absence of Waterhouse stops is because they had not yet been introduced. As I said earlier, I've learned an awful lot with this little lens.