Hi

For what is thies lens:XR HELIGON 5/100 mm? I did`nt hear that name bevor, any idea?

Thanks, Armin

-- Armin Seeholzer (armin.seeholzer@smile.ch), November 30, 2001

Answers

Armin, These seem to be for closed circuit TV cameras. They're worthless for large format. have an image circle of just enough CM to cover a TV CCD chip. I'm no authority but have gotten a couple of these along with other things I did want on Ebay. Got about 10 in a box under the car if anybody wants them. J

-- Jim Galli (jimgalli@lnett.com), December 01, 2001.

Thanks for the response Jim!

Good light and nice shadows!

-- Armin Seeholzer (armin.seeholzer@smile.ch), December 01, 2001.

To the question; "What is an XR-Heligon?"

These are very large aperture lenses intended for taking a photo of the image formed on a fluorescent screen lighted by X-rays, as in taking chest x-rays. The lenses are as fast as possible to reduce the radiation dose to the "patient" (Most such photos are made as part of screening of the general population so the subjects are not really patients under any kind of treatment.) The examples I have are F0.7 or so, making them faster than almost anything you will find on a normal camera. They are designed for a fixed reduction of size, for example 16:1 and sometimes this value is marked on the lens. Besides making photos on film, many of these lenses were used with TV cameras, but with similar purposes, allowing viewing of the insides of people, with the additional possibility of making a video recording for later study. A sensitive TV camera tube is quite sensitive so this all fits nicely together. Incidentally, in the early days of fluoroscopy the doctor eventually got sick from too much X-ray exposure, perhaps with cancer. Kinglake has a little information on this kind of lens; the first ones came from the company Wray in England.

I don't see much hope for these in large format work. In fact, with the small F-number focus is critical and and the optical axis must be well aligned to be perpendicular to the film plane (assuming the subject is flat and also perpendicular!) And the image is small; these would be better for TV work or maybe for 16 mm. The longer focal length ones might cover 35 mm and with fast film they might enable photos in pretty awful light; however, the viewfinder would have to yield precise focus to get really sharp pictures.

Bob

-- Robert Mueller (r.mueller@fz-juelich.de), March 26, 2002.