viewfinder question

Keeping in mind I am new to cameras, and only own SLR models.....Seems like most Rangefinders I see have the viewfinder off center of the lens.
Is that to keep the camera Compact/Smaller.....What I am trying to ask is, why is it not in-line with the lens.?
Thank You

Yes to keep the camera smaller and to have one range finder window, which is to the right of the lens, for the range finder and the viewfinder. The other range finder window provides the split image for focusing.

There are two issues here: the viewfinder and the rangefinder.

Originally, the viewfinder window was separate from the rangefinder windows and it was also closer to the center of the lens. Here you see a Leica IIIf that shows this:

https://www.cameraquest.com/3frdst.htm

When using a rangefinder to focus, a reflected and offset image is made coincident with a straight-ahead image. The further away that offset is, the base, the more accurate the focusing. So, ideally, the rangefinder's windows on the camera should be as far apart as possible (German rangefinders on WWI ships had a base of at least 3 meters).

When rangefinders and viewfinders were combined, the logical thing to do was move the viewfinder to the end, away from the lens.

with an slr you are looking through the lens. With a rangefinder you aren't. Therefore there is no requirement for the viewfinder to be in line with the lens. It would be nice if it was because it would reduce parallax effect BUT it is better for the viewfinder eyepiece and the rangefinder second focussing window to be as far apart as possible to give the best focus using the split image which rangefinder focussing uses. So the viewfinder is not put inline with the lens.
Rangefinders use triangulation to focus which requires two viewfinders, one the eyepiece and the second to give the triangulation. The wider apart they are the wider angle they create and the more accurate the focussing is, especially at longer subject distances.

Artillery canon use rangefinder triangulation to determine target distance and some of those use viewfinders several feet apart. And surveying theodolites use traingulation to determine distances and heights. Exact same principle in rangefinder cameras.

Yeah...great info.....Thank You

Less of a problem with the nose if you use your right eye.
Some people can use both eyes at same time.

Xmas said:

Less of a problem with the nose if you use your right eye.
Some people can use both eyes at same time.

Click to expand...

Both eyes open really only works with 1:1 viewfinders. A few cameras have them (I know the Canon P does), and there are some external VFs that are 1:1 as well.

An added benefit of the horizontal offset of the combined viewfinder/rangefinder window is that in a position away from the lens axis it is less likely that larger lenses will block your view. On the more sophisticated cameras like Leica M etc there are parallax compensated framelines that move as you focus the lens.

On the early rangefinders like the screwmount Leicas with separate rangefinder and viewfinder optics, the viewfinder window is positioned immediately above the lens. Even with a moderately sized normal lens (not to mention lens hoods) larger parts of the viewfinder are blocked. But this was not such a big problem in practice, as these cameras were commonly used with external viewfinders in accessory shoe which sit higher above the lens and thus eliminated the problem of viewfinder blockage. Some of these external viewfinders, like the Nikon Varifocal etc, had manual parallax compensation and a "zoom" function to cover the field of view of several focal lengths.