I think it is also a good commercial idea and hope that the top scopes producers will produce it soon...
David
David,
Now that Leica has chosen a different approach to improve their birding eyepieces (by limiting the zoom range) I would like to explain why I think THIS was a very good idea - and hope that it also turns out to be commercially successful. I am not saying that a long zoom range wouldn't be useful - on the contrary, I would be more than happy to see even more options than we have now.
OK, the best 3x zooms have already been extremely good in most purposes - even compared to most fixed eyepieces. Their sharpness, light transmission, eye-relief and apparent FOV at max power, together with the possibility to get wider true FOV at low powers, have made them so versatile that many users don't actually need anything else. However, there have been two downsides of zoom eyepieces:
- narrow AFOV at low end (except the Zeiss) and
- decreasing eye-relief in the middle of the zoom range
These features practically make the zoom a dual-power 20/60x eyepiece (at least for me and many other eyeglass wearers), because short eye-relief reduces FOV and viewing comfort in between the ends. Also, the increase in TFOV comes at the expense of AFOV - making the tube-like effect most disturbing at zoom setting that is probably used the most. Someone has even said that the zoom is actually a great wide-angled, high-power eyepiece with an added possibility to be zoomed down - I would have always liked it to be the other way around. Now the Leica 25-50x looks like a very promising solution: 25x wide-angled view (which shows more TFOV than a 20-60x at 20x) with very good ER (19mm) for general viewing - AND a possibility to be zoomed-in to the powers when atmospherics often destroy the image anyway. OK, admittedly there are cases when more (or less) power would come in handy, but in my experience such conditions are relatively rare.
One solution for the high-power fans to "get the best of both worlds" could be the use of Swarovski's (etc.) 2x booster, which would give the 4x range of 25-100x with all the goodies of low powers and wide angles. I use the 3x12 Zeiss monocular and from a 20x wide-angle I can get a 60x that is very close to the zoom at 60x :t:
Best regards,
Ilkka