Everyone likes to talk about magnification, field of view, "flatness", "brightness", resolution, color shift, and other aspects of the qualities to look for in a good binocular. But almost everyone overlooks one of the most basic, and in my experience, most elusive qualities: Collimation.

Good optics are not that hard to achieve, but simple physical alignment seems to escape the attention of many manufacturers. Below is an excerpt from an article on binocular performance; sorry that I don't have the name of the author to credit:

"Physical (and optical) alignment: it doesn't matter how good the lenses and prisms of binoculars are, if the individual elements are not all perfectly centered. A typical binoculars uses a minimum of 6 pieces of glass in each optical barrel. The highest quality designs may have as many as 10. Shift any one of those elements just slightly off center from the rest and it will visibly degrade the image. Then too, there are two optical barrels in each binoculars. If the barrels are out of alignment, they will deliver two slightly different images to the eyes. Our brains can compensate for slight misalignment (almost no one has two eyes that match perfectly and the compensation mechanism is built in to deal with that fact of life). However, it is a strain, and will lead to premature mental and physical fatigue as both the brain and eye muscles work to align the images. The compensation is never perfect either. We can see through slightly misaligned binoculars but we always know something is wrong. Finally the two optical barrels must be perfectly matched optically. If the focal lengths of the individual lenses in the two barrels differ at all, the two barrels will deliver images of different sizes. Again the brain can compensate, but the image will suffer, and so will you!

Physical (and optical) alignment: it doesn't matter how good the lenses and prisms of binoculars are, if the individual elements are not all perfectly centered. A typical binoculars uses a minimum of 6 pieces of glass in each optical barrel. The highest quality designs may have as many as 10. Shift any one of those elements just slightly off center from the rest and it will visibly degrade the image. Then too, there are two optical barrels in each binoculars. If the barrels are out of alignment, they will deliver two slightly different images to the eyes. Our brains can compensate for slight misalignment (almost no one has two eyes that match perfectly and the compensation mechanism is built in to deal with that fact of life). However, it is a strain, and will lead to premature mental and physical fatigue as both the brain and eye muscles work to align the images. The compensation is never perfect either. We can see through slightly misaligned binoculars but we always know something is wrong. Finally the two optical barrels must be perfectly matched optically. If the focal lengths of the individual lenses in the two barrels differ at all, the two barrels will deliver images of different sizes. Again the brain can compensate, but the image will suffer, and so will you! "

That is absolutely right. One can only compare different optical qualities (lens quality, coatings etc), once perfect collimation is no longer a variable in the equation.

A good case in point is my friends Leupold binoculars. They were a fantastic set of optics until they fell of his truck canopy. Although imperceptible in a casual inspection, they were bumped hard enough that the line of sight for the tubes were no longer convergent. Each side still worked great, but if you tried using them with both eyes you'd end up with a heckuva headache in short order.

Canuck

I look for phase-coated prisms in a proven brand mostly the Europeans (Leica, Swarovski maybe Zeiss) but I now own a pair of Pentax 8x42 waterproofs using Leica rainguards. The Minox 8x32 seem to have a pretty good following also. Good price also. sure-shot