I am always interested in communications on this list regarding binocular
magnifications. In the UK the most popular magnification is 8x40 or 8x42 and
10x are not much used. I realise that birding in Aus is a bit different to
birding in the UK but any delusions I had about you all being so fit and macho
that you could carry heavy 10x bins with ease has just been dispelled by the
recent "harness" thread!
Often 10x binoculars are so heavy that they are hard to hold steady enough to
get any advantage from the extra magnification. A harness can help with
carrying but when actually using them you really need a tripod or a Finnstick.
(I have only ever seen the latter in Finland - it is a T shaped piece of wood
which you hold at waist height and use to support the binoculars at eye height
- it really works!) The only time I could see that 10x might be really useful
is if you are, say, sea-watching, and do not have a scope. In these kind of
conditions, putting heavy bins on a tripod can be quite a revelation - the
world suddenly gets much sharper! Photographers use a tripod for good reason.
(Our first pair of "real" birdwatching binoculars were Swift Audubon 8x42 which
were huge and heavy - a tripod or more usually, a handy fencepost or rock, made
a lot of difference to the sharpness of the image)
For gloomy forest conditions then it is the objective size rather then
magnification which is important, and also particularly the depth of field,
plus close focussing and number of turns to focus.
However, the objective size of course also increases the weight, but it is
worth noting that due to improvements in technology the light gathering power
of bins has improved a lot over the last 20 years and it may no longer be
necessary to use x50 in low light. A modern 10x40 will be as bright as an older
And unfortunately, the more you pay, the better the bins are in low light -
though the marginal benefit soon starts to get very costly!
And as a footnote, Nikons are often reckoned to be very "bright" - i.e. gather
a lot of light.
The article referenced by Dave Torr is really very interesting and covers
material I have never seen before - however, it neglects to mentions depth of
field as an important characteristic. This is possibly because it is rarely
mentioned by manufacturers, so it is hard to find out how good a particular
model is, however good reviews will cover it.
Peter and Rosemary Royle