I really liked this article but I don't see an author credited. Does anyone know who wrote it?

https://www.americanrifleman.org/content/optical-resolution-how-sharp-is-sharp/

Bill McRae

Thanks Brad.

Jason

Thank you for posting that article on optical resolution 4th_point. I could never understand why my 15-60x60 older Redfield spotting scope always looked a bit sharper at around 40x than it did up at 60x until I read your article.

Since I was briefly mentioned in my old friend Bill McRae's excellent article, I'd like to point out that Bill spent a LOT of time testing optical quality in very controlled conditions down in his basement, using the USAF chart pictured at the beginning of the article. I know this partly because I joined in many of those sessions, since we only live a couple hours drive from each other in Montana. Every time we both got in a few new scopes or bimoculars, I'd drive up and we'd spend time wringing them all out.

Bill not only knew a LOT about optics (much of it learned from the head engineer of a major hunting-optics company, as well as other generous folks in the industry) but was very willing to share his own knowledge--which came not just from technical understanding but decades of hunting and photography experience. When I started writing for gun/hunting magazines, it was probably an even bet that Bill took the cover photo on any of 'em! He was also equally generous in sharing his photographic skills, and favorite places to photograph. We also spent considerable time together doing that, both in national parks and along the Rocky Mountain Front near his home.

I just wish he'd put all his optical knowledge into a book. He kept threatening to write books, both on hunting and optics, but never did--and eventually retired after writing thousands of articles, and taking hundreds of thousands of photos.

I found it really interesting too!

Over the years, I came to the rough conclusion that most spotting scopes were OK up to a theoretical 2mm exit pupil or a little more. So for a 60mm, 60mm/2mm = 30 magnification (or a little less zoom), but I never really knew why. Those observations were mostly based on budget class scopes though and not high end. But even some "alpha" scopes seemed to have that characteristic too but I haven't looked at that class in several years and it sounds like the zoom eyepieces have gotten really good recently.

John,

Thanks for posting about your friend Bill. It sounds like he was a wealth of information on optics. I was hoping that you would chime in.

Jason