View Full Version : RD gray no. 6 periscope

16-Feb-2008, 12:36
Does anyone have any experience with the R.D. Gray No. 6 periscope lens? I picked one up some time ago and just now put it on my 8x10. In fact, due to its diminutive size, I put it on my 4x5 first and then realized I did not have enough bellows.

Anyways, I have measured it to be 320mm focal length with an internal, non adjustable stop of f/16.

Please, any info on this would be great (including weather or not my measurements are correct).

Ole Tjugen
16-Feb-2008, 13:07
I have no idea about the R.D. Gray Periscope lens, but assuming it really is a Periscope I can say some general things. The fixed f:16 aperture indicates that it is.

The Periscope/Periskop is a symmetrical lens consisting of two simple meniscii. This gives good correction for distortion, but not much else. In particular chromatic aberration, spherical aberration and astigmatism tend to be bad. This is the lens compared to which the "Rapid Rectilinear" is "Rapid"!

320mm seems a little short for a No.6 lens, but I'm used to German "numberings" where No.6 would indicate an intended plate size of 30x40cm - 12x16". There's no way a 320mm Periskop would have been sold for that size - but I may of course be wrong (again).

16-Feb-2008, 14:40
Ole, thanks a ton. It also has a waterhouse stop cut in it and it does appear to be original. Then again, I could be way off on that one.

As far as its dimensions, it covers 8x10 with ease and the lens itself is 1 7/8" in diameter and about 2.5" long - quite small.

16-Feb-2008, 14:55
Gray was an optics guy in NY/NJ late 1880's - 1890's (and later )....



17-Feb-2008, 11:45
Well, that looks to be it. I guess my math at f16 was a hair off (should be f14). The odd thing is that there are no wheel stops on my lens. There is a slot for what I thought was waterhouse stops but I guess a wheel could have gone there.

What are theses worth by the way???

17-Feb-2008, 14:04
I'd gather a nice looking periscope might go for $150-200 give or take.


Ernest Purdum
17-Feb-2008, 16:23
You can probably tell whether or not it originally had wheel stops by looking for a screw hole in the existing stop and over toward the slot. This would have been for the pivot for the wheel.

17-Feb-2008, 18:51
Sounds good. I believe that there once was a wheel stop with this little feller. I also got it for $10.00