@henry link #19
Attached see a photo with a small light source reflected in the objectives of a B-type 130m version on the bottom, and a non-B 150m version above. In each case there is a reflection near the bottom, probably coming from the prism, and two reflections, close together, near the top. I believe these are what you were talking about, and I see no significant difference between the two instruments. Do you?
(Sorry for the mediocre quality of the photos I have uploaded, but it is really tricky to catch the reflections or the diagonal line without a lot of special supports, lighting, and time.)
In #30, I believe the diagram is of a B-type, but looking more carefully, I believe it shows clearly that inner elements of the ocular move for focus, not the prism assembly. I was perhaps led to my careless error by the photos of the physical cutaway example of the 8x32 cited earlier by another member. One can see a spring attached to the prism assembly, but perhaps that is the anchor end of the spring, not the active end, which might be the movable lenses.
The diagonal line seen in the non-B model is sharp, no matter what the focus setting.
I believe you are right, Lee. I was not paying sufficient attention to the color scheme. So, the prism assemblies move in both halves of the binoc, and the inner lenses of the ocular of one half move for diopter adjustment.
I think you had it right the first time. Only the first three elements of the eyepiece move for focusing. Moving the prism would have no effect on focus. The focusing knob moves the eyepiece lenses in both sides simultaneously, the diopter adjustment knob moves only the left eyepiece lenses.
I looked back at the old brochure I used to post that 7x42 cutaway a few years ago. It must be the last one devoted to the old Trinovids since it's dated August 1989. There was a little more information about the focusing which I posted below along with a better (I think) photo of the cutaway.
Henry
Only the first three elements of the eyepiece move for focusing. Henry