Possible to manufacture a Horseman 970 Rangefinder Cam?

[abruzzi]

I don't know how hard they are to find or their cost, but Horseman made a ground glass that simply fits in any graflok/internation 6x9 back. I have a couple of them as I've found them useful. I think one of them came from something I bought from B.S. Kumar so you might check with him.

 

[Chuck1]

Be careful there's one for polaroid backs(spaced further than for film)

 

[loccdor]

I did receive the 270mm Tele-Arton today. It's the (I think) newer version that looks like this:

I measured the infinity distance roughly in the 152mm range figure that I found online. Maximum extension on the Horseman 970 of 300mm puts it approximately at 0.915 meters focus. That should make it usable as a portrait lens at a fixed 1.5 meter head and shoulders distance if I calibrate its infinity stop in conjunction with the 1.5m rangefinder setting. All other distances will probably be off.

Don't yet have the lensboard or 180mm cam for it, coming soon.

 

[abruzzi]

The last version has outside printing rather than the inner trim ring.

The oldest one (I think its oldest, its a Compur shutter unlike mine or yours which are in a copal.) has more of the lens behind the the lens board than in front of it.

Schneider 270mm f/5.5 Tele-Arton Linhof-Select GOOD+

Schneider 270mm f/5.5 Tele-Arton Linhof-Select GOOD+ Very pretty 4x5 lens by Schneider. It is marked "Technika" and "Linhof". Speeds sound accurate. Glass is cl

www.seawood.shop

 

[loccdor]

@abruzzi Must be the middle version then. The flange focal distances for the 3 versions I saw floating around were 152mm, 158mm, and 178mm. Could be mine is 158mm, I used a ruler and the film plane was my sweater.

 

[loccdor]

The lens board came today and I was able to take some measurements. The 180mm cam comes tomorrow.

Schneider Tele-Arton 270mm f/5.5 Lens (middle version, black but with text on inside of ring)
On 6x9, this is the 35mm equivalent of a 115mm f/2.4
Flange Focal Distance (infinity): 158mm
Max extension with Horseman 970 when infinity stop is set correctly: 228mm, which focuses 1.65 meters from film plane, 0.14x magnification
Max extension with Horseman 970 when infinity stop is at absolute end of rail: 242mm, which focuses 1.37 meters from film plane, 0.18x magnification, infinity is lost (8.3 meters farthest focus)
Note that this is a with a flat Copal #1 board and you could get it a little farther with a special board
Also note that with the flat board the lens has to be rotated somewhat oddly so that the user has access to all the controls on the small 80mm horseman board

Infinity focus

Infinity focus stop

1.65 meters focus

Odd orientation

This is what AI calculates will happen when I use it with the 180mm cam after giving it all my data. It's interesting that it would apparently give me two usable rangefinder distances (if it's real). I'll test it.

Tele-Arton 270 mm on 180 mm Horseman 970 cam​

Infinity stop set to 158 mm​

Bellows (mm)	Δ ext (mm)	RF indicates	Actual focus	Linear error	% error
158	0	∞	∞	0	0%
165	7	14.3 m	18.6 m	–4.3 m	–23%
172	14	7.7 m	8.3 m	–0.6 m	–7%
180	22	4.8 m	5.0 m	–0.2 m	–4%
190	32	3.6 m	3.6 m	≈ 0 m	≈ 0%
200	42	2.7 m	2.6 m	+0.1 m	+4%
228	70	1.8 m	1.65 m	+0.15 m	+9%

 

[loccdor]

Previous calculation was not quite there. Too much extrapolation. Here is the real world measurement.

Using the 180mm cam, with infinity stop mis-set to maximum of 172mm at end of rail, the rangefinder is accurate at the distance of 11 ft 1 inch (3.38 m), corresponding to 10mm of extension (182mm total). That's a portrait frame 1.02 meters tall and 0.68 meters wide, a "bust" half-length type of portrait. Useful. Focus can be fixed there and used for all shots.

 

[ic-racer]

You should still be able to use the camera's built-in rangefinder. Though it won't be coupled.

With the 180mm cam in place, the rangefinder's readout on top of the camera should indicate the correct subject distance, irrespective of the lens in place.

After focusing with the rangefinder, you could read off that number and then (with a focus-rail mounted distance guide) move the lens to the matching focusing distance.

You could have the AI Bot calculate the distance scale for the lens and affix it to the focus rail. The examples I posted above were for the 4x5 FA Horseman, but something similar could be created for your lens.

BTW, that lens looks great on your camera!

 

[loccdor]

Thanks @ic-racer , that sounds like a good idea, though I'd have to be really precise with it for a 270mm lens. The rangefinder readout's difference between 10 and 11 ft is pretty much just a hair.