I want to share this email I've just received in response to our last Beacon newsletter article, How to Choose Binoculars. UK-based Beacon subscriber, Alan Brooks, has clarrified and dilated my binocular selection explanation, and if you're thinking you might be ready for a new pair of binoculars, this is a must read!

Hi George,
In response to your primer on binoculars, a few points:-

1) When you talk about the objective lens, the important aspect in regard to brightness is the size of the objective lens divided by the magnification. This gives the equivalent exit pupil size. The example of 8x32 gives an equivalent exit pupil size of 4mm. The human eye typically opens up to a maximum of 6-7mm in low light conditions and 3mm in reasonable daylight.

So, if you want maximum brightness in poor light then you need something like an 8x50. The 8x32 would probably be OK for normal daylight. This assumes that all the light possible enters the objective - ie a good anti-reflective coating. Can often be better to pay out for an apparently smaller objective lens with a good coating than something with a larger objective, but poor quality coating - it also makes for a lighter pair of binos.

2) Remember that light entering the objective is proportional to the square of equivalent pupil diameter - so going from 8x25 to 8x32 increases the light entering the binos by 64%.

3) Magnification - generally accepted that greater than 7:1 will require some sort of additional steadying to make them useful at sea. That and low light use is why the standard naval binocular is has been 7x50 for so long.

4) You can get binoculars with built in image stabilisation - allowing much greater practical magnifications for hand held devices. However, you need to match the type of stabilisation employed to the intended use. For instance, gyro stabilised devices take out shake (fast movement) and sway (slow movement) - no use at all for anyone wanting to pan their view.

5) Unless your eyesight is perfect you will need a dioptre adjustment to balance out the optical differences between your eyes (eye relief specification).

6) If you wear glasses look for a pair with long rubber cups on the eyepieces. Far more comfortable.

7) For use at sea, folding rubber objective hoods can be a good idea - they reduce glare and, if it is raining etc can keep the objectives relatively clean.

Hope that you don't mind and thanks for the newsletter, always read with anticipation, although, as you can see from the email address, I'm based in the UK.

Regards,
Alan Brooks

Thanks, Alan! It's a big help when we get this sort of feedback from our Beacon subscribers, and I hope that anyone who feels like they'd like to offer feedback, augment, edit, agree, disagree, etc. with content from our newsletters won't hesitate to get in touch with me. You can send your thoughts to editor AT shipstore DOT com.