I've always regarded it as one of the mysteries of ornitho-optics (if I can coin such a clumsy word) that the 7/9x35/36 configuration seems so popular in the USA, yet so little regarded in the UK (and Europe generally?). Witness that all posters here thus far sail under the stars-and-stripes (albeit one ex-pat Brit). In 40+ years of birding in the UK and a greater than average interest in optics I've only once come across a birder using a 35/36mm glass. Is it, I wonder, the greater influence (in marketing terms) of the hunting lobby? Similarly, although less marked than hitherto, why is it that we on this side of the Atlantic tend prefer fixed magnification lenses on 'scopes then zooms?
Hello John,
This pertains mostly to a test report I have been hunting for years, but think it may reflect some opinions here so I am going to go out on a limb. I think a lot of the 7x preference on this side of the pond may be caused by military service of us older folks.
There was an old Navy test that was referenced in the Quarter Masters official list of suppliers (Navy version of a catalog) that I read when in the service in the mid 60’s. I have been searching the web for this test report for years.
It may help to have someone else on the lookout for this information. When I was in the Navy, one of the Quarter Masters on one of the big ships showed me an article in one of his supply books. It was a test the Navy had conducted (and I can not remember the details, but was impressed by the numbers) that showed that a large group of test subjects, ages 18 to 27, mostly male but representative number of females, were tested IDing moving silhouette shapes under various conditions and distances, and standard resolution targets, and were graded on both speed and accuracy. The powers were from 5x to 12x handheld and, by a large percentage, both the ID speed and accuracy scores for the 7x won. I cannot remember the numbers but seems like it was in the 90's% range. I have been hunting for that test online but have not found it. I did find a quote from an Opticalman in another forum that looked as if it came from this test. I emailed Bill Cook about this, him being an old Navy man, thought he surely has seen this but have not heard back from him (since found he is having health problems, so did not try to call him). The quote found is:
From: vichris -> RE: Stirring the pot 8X vs 10X (11/4/2008 5:35:58 PM) an optician and Navy Opticalman. Sorry, I did not get the forum name.
The US military has studied the human body as it relates to optics. The average maximum that the human pupil will open up to is 7mm. So designing an optic with an exit pupil of 7mm would meet ANY viewing condition thus the military standard 7 X 50. They also found that 97% of the test group could HANDHOLD a 7 X bino well enough to CORRECTLY count the lines on a 7X resolution chart.............but only 8% could CORRECTLY count the lines with a handheld 10X bino on a 10X resolution chart. All of the binos had at least a 5mm exit pupil. The test group were required to use both hands, could sit, stand, or kneel, steady themselves in any way against any part of their own body but were not allowed to lay prone or use any foreign object to help steady themselves or the bino. The test group were between the age of 18-27.
As for the aperture, in my case, I think my eyes can only dilate 4.5~5 mm so a 7x35 would be about the max I could use. Right now, my 7x are limited to 7x20 and 7x42 and 7x is still my all around favorite power, that has not changed for 40 years, so I would like to have something in between.
If anyone has a copy, or knows of a source, of that test report, I sure would appreciate a copy of it.
Thanks, best to all,
Ron
