A rangefinder with variable viewfinder magnification?

[Steven Lee]

The subject says it all. Those of you who take apart cameras and examined the construction of rangefinders, can you see a way for a RF manufacturer to build a camera with a variable magnification ratio rangefinder? I have never seen one, but IIRC there was a Contax and a recent digital Fuji X-Pro that had it?

What stops Leica from making one? Or perhaps the concept of "goggles" can be improved somehow using modern manufacturing techniques and materials? How about a completely swappable VF/RF mechanism similar to prisms on SLRs?

I love rangefinders, but I find that any Leica can take just one focal length comfortably, with maybe one more as a so-so compromise, with 3+ lenses causing pain and suffering.

(inspired by "which cameras need to be re-introduced again" and Pentax getting back into film threads)

 

[OAPOli]

I think the Canon L2 (1957) did that. Three setting for 35mm (0.4x), 50mm (0.7x) and "RF" (1.4x) for more precise focus.

 

[xkaes]

There are lots of cameras that have viewfinders that change. The ones I'm familiar with are relatively simple cameras -- 110 cameras that have a normal/wide-angle pair of lenses (Kodak Tele-Ektra) or zoom (Hanimex VEF Zoom), 35mm half-frame pair (Fuji TW-3), full frame pair (Olympus Twin) or digital zoom (Nikon Coolpix 4600 & 5600).

But rangefinders? I'm sure they are out there.

 

[cramej]

Many of the Canon LTM rangefinders have that feature.

 

[ic-racer]

Yes Canon. Very clever, rotating prism.

 

[reddesert]

As mentioned many Canon rangefinders had a 3 position magnification combined VF/RF. However, these don't have projected framelines; the later ones with framelines (I think VI, P, 7) don't have the variable magnification.

There are a lot of VF-only viewfinders with continuously variable magnification, like multi-focal shoe mount finders, the Linhof multifocus finder, and zoom finders in AF P&Ses, digicams with optical viewfinders, and so on. I'm not aware of any of these that also have an RF patch, and that seems likely to be challenging, but I don't know every possible camera out there.

 

[reddesert]

There are a lot of VF-only viewfinders with continuously variable magnification, like multi-focal shoe mount finders, the Linhof multifocus finder, and zoom finders in AF P&Ses, digicams with optical viewfinders, and so on. I'm not aware of any of these that also have an RF patch, and that seems likely to be challenging, but I don't know every possible camera out there.

I haven't been able to find an optical diagram of how the Canon switchable magnification works (rotating prism), although it may be out there somewhere. For continuously variable zoom finders, I think simple ones are usually a 3-lens system where one of the lenses moves forward/back.

To expand on what I wrote, I think the problem with a combined RF/VF that changes magnification is that you have to ensure that the magnification remains equal between the two rangefinder windows, and this is not easy.

 

[ic-racer]

I haven't been able to find an optical diagram of how the Canon switchable magnification works (rotating prism), although it may be out there somewhere. For continuously variable zoom finders, I think simple ones are usually a 3-lens system where one of the lenses moves forward/back.

To expand on what I wrote, I think the problem with a combined RF/VF that changes magnification is that you have to ensure that the magnification remains equal between the two rangefinder windows, and this is not easy.

I looked too. The service manual is available, but does not show it well. Can't find a youtube video of any one taking one apart and cleaning it either.

 

[cramej]

I looked too. The service manual is available, but does not show it well. Can't find a youtube video of any one taking one apart and cleaning it either.

What is it you want to know about the Canon system? It is a rotating prism and the RF patch is magnified when you change views. On the older cameras, the magnification is the 50mm view, 90/100mm and 135mm. You can also use the magnification to focus more accurately since the patch is also larger.

 

[reddesert]

What is it you want to know about the Canon system? It is a rotating prism and the RF patch is magnified when you change views. On the older cameras, the magnification is the 50mm view, 90/100mm and 135mm. You can also use the magnification to focus more accurately since the patch is also larger.

I was curious about the optical layout and how the change of magnification is accomplished. I have one of these RFs (Canon L2) but don't really want to take the top cover off a working camera just to look.

I was wondering about the "rotating prism." I had thought that was somehow rotating to select the magnification, which puzzled me. However a rotating prism is a type of RF mechanism. On a close reading of Stephen Gandy's page on the VT at https://cameraquest.com/crfvt.htm it seems that he says the selector actually changes between three different rotating prisms for the three magnifications. (There would also be a lens for each, because the prism itself doesn't magnify, it changes the angle of the light beam).

Rick Oleson has a nice article explaining how viewfinders and rangefinders work at http://rick_oleson.tripod.com/looking_forward.htm
Reading that carefully, just above Figure 6 (the diagram of the Leica II rf), he says that the RF/VF has viewfinder lenses mounted behind the entire RF system, and on the Canon these are pivoted to change the magnification between 0.66x, 1x, and 1.5x (respectively reverse-Galilean, no-lens, and Galilean finder arrangement). That isn't the same as Gandy's description but may be more practical.

 

[cramej]

@reddesert I'll take the cover off of one of mine and get some detailed photos to share soon.

 

[cramej]

@reddesert I was incorrect - it is a rotating lens and mask assembly, not prism. There are 2 lenses and masks on the rotating cube shown. This particular camera - that is waiting for me to repair it - actually needs to have the rotation adjusted because it doesn't fully lock into the detent of the F(ull or 50mm) view like it should (first photo). The small circular mask is the 1x (90/100mm) and the lenses and mask are reversed from the F setting to give the 1.5x (135mm) view.

You can see in the first 3 photos the rangefinder prism to the right at the front of the top plate.

 

[Hunter_Compton]

The Kodak Ektra had a continuously variable viewfinder window to accommodate lenses from 50-254mm in focal length.

This was accomplished by a system using 5 objectives, 4 of which moved to accomplish different things. (one moved for parallax compensation, one moved to adjust focus to the user's eyesight and two moved as a group to vary the focal length.

The rangefinder was split image prismatic and separate, using two objectives and 4 prisms.

 

[Timo Schön]

The Contax G2 also does this I think but I have never held one and just read it somewhere - also I am not even sure if it is considered a rangefinder camera

 

[reddesert]

@reddesert I was incorrect - it is a rotating lens and mask assembly, not prism. There are 2 lenses and masks on the rotating cube shown. This particular camera - that is waiting for me to repair it - actually needs to have the rotation adjusted because it doesn't fully lock into the detent of the F(ull or 50mm) view like it should (first photo). The small circular mask is the 1x (90/100mm) and the lenses and mask are reversed from the F setting to give the 1.5x (135mm) view.

You can see in the first 3 photos the rangefinder prism to the right at the front of the top plate.

View attachment 326287 View attachment 326288 View attachment 326289 View attachment 326290 View attachment 326291

Thanks for these pictures! This is the arrangement that Rick Oleson diagrammed in his writeup I linked above, where the (variable magnification) eyepiece optics are entirely behind the rangefinder part. My guess is that for later RFs with larger viewfinders, eyepieces, and higher eye relief, that an arrangement like this would get quite large, and maybe that's why subsequent cameras don't use it.

Also, people may have felt that projected framelines gave greater framing accuracy, I don't know but I thought that was one of the selling points when RFs with framelines became available.

 

[Timmyjoe]

I think the Canon L2 (1957) did that. Three setting for 35mm (0.4x), 50mm (0.7x) and "RF" (1.4x) for more precise focus.

Yes, I have a Canon L2 and it definitely has the viewfinder magnification. It's a nice little feature, especially when shooting 35mm as the viewfinder also zooms out from .7X magnification at 50mm to .4X magnification at 35mm, which makes accurate focusing difficult for me. Zooming in to 1.4X magnification makes it easy to nail focus.

Best,
-Tim

 

[Sammydesinas]

Yep the Canon L1/VL/VT have this. Great to not have to get an auxiliary viewfinder.

 

[Jonathan-sv]

A Canon L2 and a Jupiter 12 was my 'poor mans M2' setup for a while. I bought it specifically for the 35 mm viewfinder though it's not as bright as an M2.

 

[armadsen]

The Hasselblad Xpan cameras (aka Fuji TX-1/2) are rangefinders that have a VF with variable magnification and an integrated rangefinder patch. There are only two magnifications, one for the 45mm lens, and one for the 90mm. The 30mm lens uses a separate detachable top-mounted view finder.