Rangr finder window, windoe

[33dollars]

The rangefinder camera comes with a viewfinder window. & a second window to find range.
What is that second window called?
Some of my RF's have a comparable sized window to the viewfinder.
But I have just noticed that my Royal 35-M has a Incy Wincy rangefinder window. Where as some of my cameras have a opaque window. Some have Cds metering. Most have none.
Russian stuff with distance between the viewfinder to second window & short distance on 70's Japanese cameras.
I guess what I'm asking is, what's the best of the average to RF? What is required to do the job?
Here is a picture of my Royal 35 with cheese


And here is another from three years lattera

[mickeyobe]

Two windows (Points of view) are needed for a rangefinder to work. I would call the second window the rangefinder window.
We use both our eyes to judge distance. Try closing one eye and you will see that everything appears to be on one plane. So too with the camera rangefinder.

The opaque window is used to project frame lines onto the viewfinder image. Sometimes that frame will move to correct parallax.

Some R/F's have a superimposed rangefinder in which two similar images are used. One of them is moved until it is perfectly located over the other. This type usually uses an Incy Wincy window for the secondary moving image which is generally tinted.

The Incy Wincy window is sometimes located in the centre of the opaque window thus combining two functions in one window.

The split image rangefinder cuts the image in two horizontally. One of the images is moved until it matches up with the other thus forming a single complete image. It too may use an Incy Wincy window which is sometimes a narrow slit.

Either type of R/F may use either window.

None of the above windows has anything to do with the metering. On your Royal camera it is the one with the flap that is the meter's window.

Some R/F cameras have separate windows at the back for viewing and focusing.

Some very old cameras may have extinction type light meters but let's save that window for another thread.

Mickey