I have a 480mm Nikon Process lens with a slot and sliding lever to cover this slot. Can anyone tell me what and why this is for and why the numbers (which see to corrispond to degrees)?

Thanks in advance to all those who reply and those who don't but who have contributed to this wonderful forum and increased my knowledge of LF photography immensely.

Matthew

-- Matthew Hoag (hoagm@bostonpizza.com), March 19, 2002

Answers

I own the same lens.

The lever has no use for regular photography but had a function for making color separations. The Waterhouse f.stop plates (if you have them) are great for precise exposure - again when making color separations. For all practical purposes you do not need these to use your lens. Instead use the standard diaphragm that stops down from f:9 to f:128. If you do use the Waterhouse f stop plates you will get extremely fine pinpoint specular highlights - perfectly round...

This lens will cover 11X14 and is incredibly sharp - as you may have noticed.

-- Per Volquartz (volquartz@volquartz.com), March 19, 2002.

The stop plates are scored and can be punched out to form square openings of different sizes.For photo-engraving they can then be pushed into the slot and rotated for a range of 45 degrees in order to place the square in different relative positions to the screen lines.

-- Merg Ross (mergross@aol.com), March 19, 2002.

Nearly all process lenses have this facility for using shaped stop inserts. It was never really meant for round stops.
As Merg says, the plates had square, or sometimes diamond-shaped apertures punched in them. This gave a more precise shape to the halftone dots that the lens had to reproduce for process platemaking.

In colour separation work, the screen orientation is rotated to a different angle for each of the four CMYK plates. The stop was also rotated to line up with the screen.
Sorry for reiterating much of what was said above, but I didn't think that the purpose was properly explained in the previous posts.

-- Pete Andrews (p.l.andrews@bham.ac.uk), March 20, 2002.

What a coincidence. A 480mm f9 Apo-Nikkor just fell into my lap today!(and only 25 dollars fell out). What a nice looking, but huge chunk of glass. What size shutter do these need? It way looks too big for my #4 Betax

-- Wayne (wsteffen@skypoint.com), March 20, 2002.

"It way looks too big for"

Geez, am I a valley girl or something?

You know what I mean...

-- Wayne (wsteffen@skypoint.com), March 20, 2002.

Pete, thanks for clarifying my jumbled post. Yours makes sense. Cheers, Merg

-- Merg Ross (mergross@aol.com), March 20, 2002.