Watching Nightjar on Roydon Common at the end of August with my Trinovid 8X32 bins I found myself lusting after a brighter, wider view. Thinking I might get this in a more up-to-date 8X bin by upgrading to larger objectives I started studying the manufacturers spec sheets (Leica, Zeiss and Swarovski). It turns out that the FoV of the 40 to 50mm objective bins are narrower than my Trinovids. So, the only measurable performance improvement would be an increased Twilight Factor from 16 to 18.3 -19 for 40 / 42mm or 21 - 21 for 50 / 56mm objectives. And this, according to some Forum posts, translates to an extension of viewing of about 5 minutes at dawn and dusk. The less easily judged factors, though no less important, such as sharpness, CA, field-of-view, focussing ratio, build quality, feel-in-the-hand, are going to have to add up to a significant improvement to justify the 30 - 80% extra weight and the sizeable wodge of dosh involved in upgrading. And then, I don't really need my bins to ID a flying Nightjar at dusk anyway.
Incidentally, when did the Roydon Nightjar depart? I saw them on Aug 26th. Any advance on that?
(How's this for a mixed topic?)
i have the trinovid 10x42bn model, and have found them to be the perfect allround bino. i have walked miles with them around my neck and suffered no aches or pains, they have a twilight factor of 20.5 so are bright enough to take you well into dusk! and the 10x magnification comes in very handy when youre searching or tracking for birds in the distance. the field of view and price are not much different from your own 8x32s. i would highly recommend the 42s over the much larger and more expensive 50s! just thought id share my opinion, the decision is yours at the end of the day!
7 x 42 is the way to go for a brighter image