Let's play "What the heck is this?"

[mgb74]

OK, it's labeled "Rangefinder" and has a rotating disk with various f-stop markings. One of the settings has 2 openings. With my highly refined skills in deduction, I assume it's a rangefinder or at least depth of field viewer. But the view is not focused at infinity; in fact it seems to focus at about 2". The board is 3.25" square.

 

[AgX]

Thank you, this double aperture is something to contemplate on.

Well, at first thought it is a combo of a focusing aid and a 90mm lens with variable aperture.

 

[cramej]

Wouldn't the 2 images from the double-opening aperture converge when an object is in focus? I suspect that there is something missing from this 'rangefinder' or it is to be attached to the lens of a bellows focusing camera of sorts.

 

[AgX]

It either is to substitute a 90mm lens with same principle plane or to be used for both, focusing and taking.

 

[Alan Edward Klein]

The copper bridge on the back seems to short out pins on a second device not shown to indicate to it where you turned the f stop dial settings. Sort of like a lightmeter.

 

[AgX]

The "copper bridge" is just a spring with a pin to lock the aperture disc in position for the respective apertures.
The respective hole for that pin you see in both photos at the rim of the disc.

 

[mgb74]

Wouldn't the 2 images from the double-opening aperture converge when an object is in focus? I suspect that there is something missing from this 'rangefinder' or it is to be attached to the lens of a bellows focusing camera of sorts.

I thought at first it might be intended to replace the board and lens on a Speed/Crown Graphic when taking a reading. But the board is not the right size.

The "copper bridge" is just a spring with a pin to lock the aperture disc in position for the respective apertures.
The respective hole for that pin you see in both photos at the rim of the disc.

Correct.

 

[Bill Burk]

Oh, the RF setting gives a double image that’s easy to focus. Then you select an aperture and put the film in.

 

[removed account4]

Oh, the RF setting gives a double image that’s easy to focus. Then you select an aperture and put the film in.

will it really give a double image? sink strainer apertures for imagon lenses are like 20 openings and they only give 1 image
im clueless but my guess is its just a weird aperture might give a softish image. lots of weird stuff back in the day.

 

[AgX]

Yes, I am still at my second thought. And still got no idea how to reason my first thought.

 

[Bill Burk]

Popular Photography handbook 1951

 

[removed account4]

wow. that's something else ! thanks bill!

 

[Bill Burk]

Even funnier is the lower left corner where it says “half moon shapes are best”... because that’s what this gadget has.

 

[AgX]

I even got an SLR that has such finder image but no description anywhere how it works, likely there there is a relay optic with a double aperture.

At my first thought on this thread I had macro-stereophotoography in mind where one can put such aperture in front of a taking lens, but that was hard to deduce to a focusing aid.

 

[grahamp]

This might be worth trying in some cases - easy to test anyway. Fascinating.

 

[mgb74]

So now I wonder if this is intended to held onto the front of the lens while focusing. Though only one of the apertures has the 2 cutouts.

 

[mshchem]

I wonder if Pop Photo guys just took a extra picture of the stop sign and jiggled the camera? I'm not doubting the conclusion, just saying that the picture is nonsensical.

 

[mshchem]

OK, it's labeled "Rangefinder" and has a rotating disk with various f-stop markings. One of the settings has 2 openings. With my highly refined skills in deduction, I assume it's a rangefinder or at least depth of field viewer. But the view is not focused at infinity; in fact it seems to focus at about 2". The board is 3.25" square.
View attachment 274920 View attachment 274921

My guess is it's a 90mm lens, on a 3.25" lens board, the "rangefinder" bit is the double half moon thing, like the magazine says. The other are different aperture openings for the lens. Some sort of cheap thing to sell when no one had money.

 

[Bill Burk]

There’s two on eBay right now. One just like yours and one with a round mount. I really wonder how they would be used but starting to think...

It might be an enlarger lens.

 

[AgX]

So now I wonder if this is intended to held onto the front of the lens while focusing. Though only one of the apertures has the 2 cutouts.

To me it is intended as taking lens with benefits.

However the lens seems primitive, and on which camera with focal plain shutter you would put such lens?

 

[mgb74]

There’s two on eBay right now. One just like yours and one with a round mount. I really wonder how they would be used but starting to think...

It might be an enlarger lens.

Interesting. Neither listing gave any indication of how it's actually used.

 

[reddesert]

When a lens is out of focus, the blurred image is blurred by the shape of the pupil stop. For a normal lens, that's a roundish aperture. For the rangefinder double aperture stop, it will be two separated apertures, so the blurred image will be doubled. When the image is brought into correct focus the images will merge. It's the same general principle as how a split-image focusing screen uses prisms to compare light passing through two different sides of the lens.

As AgX says, this has to be a taking lens with an extra feature. You couldn't focus with this lens and then swap out another lens, as the focus position would shift. The other aperture positions are Waterhouse stops and I guess that it's quite old, likely used on a camera with a ground glass and interchangeable lensboards, and a focal plane roller blind shutter. It would have to be a smallish camera (2x3 inch or smaller) for a 90mm lens to cover, though.

 

[mgb74]

I don't think this is a taking lens; it's a simple, plastic lens element.

 

[grat]

Are you sure it's plastic? The font, particularly the "f", looks like this thing pre-dates, well, plastic. The two on eBay are more glass looking as well.

I've got two guesses... it's either an accessory for finding range / DOF for a matched lens, or it *is* a taking lens, with a range-finding aperture as an option. Either way, I'd be looking for a late 19th, early 20th century American camera manufacturer that made cameras that take square and round lensboards.

That's assuming it's for a camera-- but a camera's about all I can think of that would care about range *and* depth-of-field.

 

[AgX]

I don't think this is a taking lens; it's a simple, plastic lens element.

As a focusing aid the regular apertures make no sense.