Rangefinder base length

[jtzordon]

I have read countless thread discussing base length and focusing accuracy. I don't think I've ever seen anyone discussing how the view is different, or if it is at all. I used a Yashica GSN, Zorki 4, and Canonet in the distant past, and never noticed a significant difference in the viewfinder. Now I own a Bessa R, but it's been long since I've used the others.

So I guess here's the question: how does base length show up in the viewfinder? Or does it? Would a camera with a longer base length have a greater separation between the RF patch and the image?

 

[ferider]

Would a camera with a longer base length have a greater separation between the RF patch and the image?

At the same magnification, yes. Interesting question.

Roland.

 

[Sparrow]

It isn’t visible in the finder, the only difference it makes is in the tolerances the manufactures needs to hold to make it accurate

In some respects its harder to focus with a wider base on some occasions, try focusing a on a tiled surface at an angle with a wide based RF

 

[ferider]

Stewart, I would think, when out of focus by the same distance, the delta between patch and viewfinder does depend on the baselength. No ?

 

[jslash6]

when i moved from an R2a to a ZI i definitely noticed an increase of the speed at which the RF shifts from side to side as one turns the focus on the lens. and as sparrow noted at low angles, receding lines appear to cross each other at the point of focus rather than line up parallel. other than that the magnification, field of view, and frame lines all seemed very similar.

 

[Sparrow]

Stewart, I would think, when out of focus by the same distance, the delta between patch and viewfinder does depend on the baselength. No ?

I don’t know the term “delta” in this context, sorry, however I use this cutting mat to check my stuff and it gets progressively more confused as the base lengthens.

 

[raid]

It is the same in the end [what was said above].

 

[Sparrow]

The more separation between the left/right images, the more accurate and easier it is to align them (achieve focus).

The only thing I can see in the finder that makes any appreciable difference is magnification.

I find a r3a easer than an m2, and a r2a more difficult than an m3
🙂

 

[sniki]

The more separation between the left/right images, the more accurate and easier it is to align them (achieve focus).

I completely agree to anything; yuo are into question.

 

[ferider]

How about this ? I leave the basic trigonometric proof of a near linear dependence of delta on b up to you guys 🙂

Or, if you have an Oly XA and a Leica, just try it out 🙂

Roland.

 

[Sparrow]

I agree completely with the geometric proof, Roland, but unfortunately I can’t see that diagram through the VF just the little patch that I find easer to use the more it’s enlarged, sorry.

 

[Al Kaplan]

It's a function of base length times magnification. 0.7X magnification of a rangefinder with 70mm between the center of the front windows has an effective base length of 49mm (0.7 times 70), the same as having 49mm between the centers of the windows with no magnification.

The mechanics of the system have to be built to tighter tolerances when you increase magnification rather than the distance between the windows. The short lived Kodak Ektra from back in the late 1940's had a tremendous base length. The old screw mount Leicas had a short base length and high magnification. The basic body, shutter, and control layout were designed before the the cameras were equipped with built-in rangefinders. The rangefinder on these cameras was designed to fit between the shutter speed dial and the rewind knob so there was no choice without a complete redesign of the camera.

 

[freax]

Hi.

In pratical terms there is some difference between r3 VS r2 ?
Can we get unfocused photos in r2 that would be sharp in r3 ?

Thanks in advance.

 

[FallisPhoto]

I have read countless thread discussing base length and focusing accuracy. I don't think I've ever seen anyone discussing how the view is different, or if it is at all. I used a Yashica GSN, Zorki 4, and Canonet in the distant past, and never noticed a significant difference in the viewfinder. Now I own a Bessa R, but it's been long since I've used the others.

So I guess here's the question: how does base length show up in the viewfinder? Or does it? Would a camera with a longer base length have a greater separation between the RF patch and the image?

I think it would depend on how close to your subject you were. We're talking about 1 or 2 inches difference at most and that just isn't going to show up unless you're shooting at something close to the minimum focusing distance.