Waiting for some sensitized carbon tissue to dry, I thought I'd play around in the back yard with a Wollaston 355mm meniscus lens. Pulling the water stop out while looking from the back of the camera, I noticed this interesting effect, so I made an exposure.
@awty I'm guessing that Andrew is referring to a Waterhouse stop - a replaceable disk that has a fixed size of hole. In order to change one's f/stop, one switches out one Waterhouse stop with another (with a different size hole.
Andrew: is this the lens you were using at Tynehead?
Yes thanks, Matt. Waterhouse. The same lens. Pulled it out from its slot slightly. Got to find a ND filter for it. Just too bright out the to control the exposure. Cap off cap on in one second is difficult.