A recent thread on a German forum brought up this subject again and a reply by Holger Merlitz stated what should have been obvious all along, i.e. that it's not really technically feasible.
I'm sure that many birders who frequently use a scope have often wished for long distance binocular viewing, but 15x magnification seems to be the upper limit for quality birding binoculars. Although this magnification could be comfortably used on a monopod, it's really not adequate for viewing water birds, unless one is gifted with 20/10 vision. There are two or three really good 15x56 or 15x60 available but unfortunately all have inadequate or marginal eye relief.
The binocular telescopes such as the Kowa High Lander, Docter Aspectem, Vixen BT70 ED or the latest Chinese ED binocular telescopes all have individual focussing, which rules out, or strongly restricts their use for birding.
Wouldn't it be nice to have something like a 25x75 or 30x75 binocular with central focussing? BUT at the same distance a 25x binocular has about one tenth the depth of field of an 8x binocular. The mechanical precision required to attain synchronous movement of the oculars or IF elements would be so high as to place the binocular beyond the financial reach of most potential customers. One now recalls complaints of rocking focussing bridges on Porro bins, unstable dioptre settings on IF bins and the varying torque clockwise/anticlockwise on some Swarovski bins, which is probably accounted for by preloading of the focussing elements to ensure synchronicity.
In retrospect, Swarovski's decision to equip a single scope objective with a binoviewer (BTX) was the only feasible solution.
John
I'm sure that many birders who frequently use a scope have often wished for long distance binocular viewing, but 15x magnification seems to be the upper limit for quality birding binoculars. Although this magnification could be comfortably used on a monopod, it's really not adequate for viewing water birds, unless one is gifted with 20/10 vision. There are two or three really good 15x56 or 15x60 available but unfortunately all have inadequate or marginal eye relief.
The binocular telescopes such as the Kowa High Lander, Docter Aspectem, Vixen BT70 ED or the latest Chinese ED binocular telescopes all have individual focussing, which rules out, or strongly restricts their use for birding.
Wouldn't it be nice to have something like a 25x75 or 30x75 binocular with central focussing? BUT at the same distance a 25x binocular has about one tenth the depth of field of an 8x binocular. The mechanical precision required to attain synchronous movement of the oculars or IF elements would be so high as to place the binocular beyond the financial reach of most potential customers. One now recalls complaints of rocking focussing bridges on Porro bins, unstable dioptre settings on IF bins and the varying torque clockwise/anticlockwise on some Swarovski bins, which is probably accounted for by preloading of the focussing elements to ensure synchronicity.
In retrospect, Swarovski's decision to equip a single scope objective with a binoviewer (BTX) was the only feasible solution.
John
