BirdForum is the net's largest birding community dedicated to wild birds and birding, and is absolutely FREE!

Register for an account to take part in lively discussions in the forum, post your pictures in the gallery and more.

Reply to thread

Message: <blockquote data-quote="Jeff Bouton" data-source="post: 989039" data-attributes="member: 14925">Neat idea but I have a few points that I'd like to add. Exit pupil is of course not that telling when comparing across brands unfortunately. Being a simple mathematical formula (diameter of objective lens divided by power), every binocular with the same nomenclature (7x42 for example) will have the same exit pupil be it a $20 binocular or $2000. So in this case, both have a 6mm circle of light entering the eye (42/7=6) but from experience we all know the better quality bin will deliver a much brighter image with superior resolution. So exit pupil is useful but only in instances where all else is equal (e.g. with in a given line of binoculars only). Each manufacturer uses a different type and quality of glass with different levels, and qualities of lens coatings in every different line they offer. So exit pupil (and other mathematical specifications) should only be considered when comparing apples to apples to be useful or in this case binoculars in the same line by the same manufacturer. Unfortunately, even specifications like eye relief are not comparable across the board because there are not universally accepted industry standards on testing these specs. As such, you can often find examples of 18 mm eye relief that are comparable to other manufacturers 15 mm measurement and vice versa. However, to get back specifically to brightness for a moment. When you stare into the sun it is REALLY bright right, or a halogen lightbulb even... too bright. It is important to consider that there is some types/intensities of light that our eyes can't process effectively. I've heard this bright white light referred to as non-image forming light in the past.The coatings on a quality optical system should transmit as much of the usable light wavelengths as possible, with as little color aberration as possible, BUT still reflect the blinding white light. An optical instrument that transmits much of the latter will certainly score well on the card test and when you hold them to your eyes you will think, "WOW these are bright". Unfortunately by blinding your eye to a degree the subsequent image will show much less contrast and resolution than a high quality product that may not appear as bright reflecting off the card. I think this is the idea behind driving glasses.As a result, the best test is still to find the darkest spot you can find with a lot of detail and use your eyes to assess the balance of light transmission and resolution. You need both for your optic to be effective. Try to find a dark spot under a bush with lots of leaves or gravel, etc. where you can look closely at the edges and assess both the light transmaission and the resolving power. One without the other is no good. What good is a brilliant image of a bird etc. if you can't assess the markings?Best,Jeff Bouton</blockquote>

Verification