Originally Posted by chill6x6
It is my belief that anything less than 5 or 6 % difference probably won't be noticed by the vast majority of users if one doesn't know binocular "A" has higher light transmission over binocular "B." Myself included.
I'm not even sure what 100% actually means in terms of our ability to detect a light source at full strength, since even our own eyeballs are reflecting some percentage of light. Is our cornea not to be considered an 'air to glass' surface? Furthermore, if one is wearing glasses, you have to add 2 additional air to glass surfaces, which, I can attest, do play a role in affecting one's image, even when NOT using binoculars..
Chuck states that a 5-6 percent difference might not be noticed in a blind test. Consider that in comparative percentages, a difference of 85 to 91% in light transmission is actually 6.6% (85/91)
For the internet shoppers, the spec based approach can really play a frustratingly devious role in trying to find the right binocular. If you think of a binocular like an item of apparel that is built to a certain level of quality, then issues like weight, IPD, and eye relief are probably the most important one's to consider. The physical fit to your eyes, hands, and face are pretty crucial. I would include FOV in that, but I'm starting to even question some of the logic in that.
For example, the notion that a wider field confers a 'big' advantage at close range seems entirely rational until one starts to look at the numbers a bit.
Binocular 'A' has a 372' FOV at 3000'
Binocular 'B' has a 430' FOV at 3000'
That's a 58' difference..... at 3000' It looks BIG on paper until you realize that difference only exists over a half mile away.
Where I bird, I consider close range viewing to be around 100' or closer, at which point the relative difference is 1/30th of 58', or 23.2 inches. Consider that a highly caffeinated target warbler is centered in your view, and it jumps out of the field to another spot in the foliage. Since it can only exit one side of the image circle at a time, the difference at any point on the perimeter is less than 12", or a little over 2 warblers stacked end to end. The closer you get, the difference gets ever smaller. I'm not saying there is no practical advantage to a wider field, but the spec numbers can imply a gain much greater than what real world use might reveal.
Another point to consider is whether eye relief, whether wearing glasses or not, allows one to see the entire field, at which point there may be no wide field advantage at all to be had, even if the image quality is wonderful.
Just some food for thought.