Use for a Wollensak 3" (75mm) f1.9 oscilllo raptar 1:0.9X

<p>Hello everybody,</p>

 

<p>I was just wondering if anyone can clear something up for me. I've

got this lens that states that it's a Wollensak 3" (75mm) f/1.9

Oscillo Raptar 1:09X. When I set the lens to infinity, all I get is a

really small image circle (about 70mm, or just under 3" in diameter).

When I set the lens out farther and cover the whole film area, then I

get a very sharp and bright macro lens. So my question is this a

dedicated macro lens or is it for a smaller format camera? Any other

information pertaining to this lens would also be greatly appreciated.</p>

 

<p>Thank you all in advance for your assistance.</p>

 

<p>R.M.</p><div></div>

This lens is intended for use with one of the smaller speed/crown graphics (the 6x7 or 6x9 format ones) that use a graphlex roll-film back. It was not intended to be a wide-angle for 4x5. The lens speed, among other things, should be a clue to this. Most 4x5 lenses are f4 or f5.6 or slower. The image circle being just 70mm at infinity is the biggest giveaway that this is a medium-format lens.

The name is the clue to the intended purpose: it was for photographing oscilloscope screens. Since the screens have dimensions of a few inches, it is effectively a macro lens. Most likely it was used to make photographs onto Polaroid prints of size a bit smaller than 4x5 film. If you wanted to photograph a single oscilloscope trace, a fast lens was needed -- the finite duration of a single trace means that you can't get more light be increasing the exposure time.

 

The "1:0.9" is telling you the intended reproduction ratio, further evidence that this is a macro lens.

 

Now days this usage is disappearing, being replaced by digital oscilloscopes that can produce a file with the screen image.

 

So you can use it as a macro lens on 4x5, but as you found it won't cover at infinity. The correction at infinity would also be poor.

This lens was used in oscilloscope cameras for Polaroid roll film. Speed was the important issue, the osciloscope screen is not very bright when a single fast trace is being photographed. The trace has no very fine detail, so high resolution was not needed. This lens has little use for general photography, although the shutter may find use.

Scott, I haven't hefted one for a while, but I believe that a 3" Oscillo-Raptar's rear cell won't pass through a 2x3 Graphic's lens throat. There were no 6x7 Graphics. There were nominal 6x6, 6x7, and 6x9 roll holders for Graphics. Also, it takes an 80 mm circle to cover the nominal 6x6 format.

The oscilliscope cameras originally took Polaroid roll film, but later models took the 100-series pack films. Typically 107, for obvious reasons. As the Land List site notes, the actual image area was 2 7/8" x 3 3/4" (7.2 x 9.5 cm). Typical oscilliscope screens were sized up to 10 x 12 cm.

 

A really good oscilliscope could have a spot size of say 0.2 mm. So the resolution demands are minimal. The lens probably is good in terms of flatness of field and freedom from distortion.

 

Nice big shutter, probably the most practically valuable part of the lens. The lens won't even cover 6 x 6 cm at infinity, as you've seen.

 

Someone probably parted out a oscilliscope camera that had a Polaroid roll film back. There's only a minimal market for the ones with the pack film back, and zip for the roll film backs. (I have one of each, I bought the roll film one for my Tektronix oscillscope not knowing it was a film orphan.) There were a very few with Graflok backs, probably long since scrapped for the back.

 

Some cameras even had facilities for pre-flashing the film to increase film speed, a slight base fog was OK. Hewlett-Packard made some with a UV light that made the phosphors on the screen flouresce.