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View Full Version : 305mm f/9 Apo-Nikkor Question



Bob Fowler
4-Dec-2003, 20:46
Not to sound like a moron, but I have limited experience with process lenses in barrel.

I recently acquired the aforementioned 305mm f/9 APO Nikkor (I assume it's an older model because it's marked "Nippon Kogaku Japan" on the trim ring and not "Nikon"). Anyway, above the aperture ring is something that has me puzzled. There is a slot which covers approximately a 135 degree arc. Along 90 degrees of that slot, there is a scale calibrated from 0 to 90, with tick marks every 5 degrees. Now for the part that has me perplexed... there is a post which travels through the slot over the full 135 degree arc. What in the name of all that's gooey IS this? When I first saw this, I though it may be linked to the iris (it's not), or that it might move one of the internal lens elements (I can't tell). Does anyone know what this is for or what it does?

Thanks in advance!

Bill Kantor
4-Dec-2003, 21:02
Could that be a slot for filters or waterhouse stops?

Ernest Purdum
5-Dec-2003, 10:17
Bill Kantor is right, this is a slot for Waterhouse stops of a rather special type. In photogravure, the shape of the aperture opening is that which will become the shape of the little dots that make up the image. Square or diamond shaped dots are preferred, so a special Waterhouse stop with a square opening may be used. Rather than a whole set of stops, one plate adjustable in size could be provided, and that's what you are looking at here.

Bob Fowler
5-Dec-2003, 13:30
Thanks guys... I just noticed that when the post is moved all the way CCW, it opens up the area where a waterhouse stop can be inserted.