A question about depth of focus...

[rhsc]

...or maybe depth of field is the correct term. This is in regard to roof prism binoculars specifically.

I've been comparing my Athlon Ares ED 10x42 binos with a set of Meopta Optica HD 8x42's. The Athlon perform just a bit better in nearly every respect except they don't have the broad depth of focus that the Meopta have. Looking at objects at @ 60 and 110 yards, there's no need to adjust the focus of the 8x Meopta, but the 10x Athlon does require a small adjustment to see both objects clearly. It just so happens that range of distances is where I take most of my shots while hunting, so having them (and everything in between) in focus at the same time is a big advantage.

Is that typical to see when comparing binos of different power? Does lower magnification provide a greater depth of focus or is that a characteristic determined by the manufacturer's design choices?

The reason I ask is that the 8x42 Athlon is on sale right now at a very good price, and if I could be assured of the same sort of generous focus as I see in the 8x Meopta, along with the otherwise nicer performance of the 10x Athlon, I would buy them. But if they're no better or only marginally better than the 10x Athlon in that regard, I would have to take a pass on them.

 

[Rocketvapor]

Depth of field - Wikipedia

en.wikipedia.org

The depth of field can be calculated based on focal length, distance to subject, the acceptable circle of confusion size, and aperture.

Focal length - Wikipedia

en.wikipedia.org

 

[rhsc]

Thanks. What I get from those links is that the effective focal length is probably what most determines the depth of field.

However, my question about the specific binos I'm looking at still stands. Maybe I just need to call Doug at Camera Land tomorrow and get his opinion since he's running the sale on the 8x Athlons I'm considering.

 

[338LMAI]

When conferring with Doug ask him about comparing a 10x to a 8x--both being with 42mm objective lens regarding depth of field. Generally as the magnification increases the depth of field decreases. At least that's been my experience with telephoto lenses, but maybe this is different as with a camera there's the arpeture size that factors in significantly (f2.8 300mm will have much less depth of field than when set at f5.6--or a f6.2 200mm, etc.). However, for me that's advantageous because, coupled with the added magnification, details the view more explicitly.

 

[rhsc]

I called Camera Land today and spoke to Neil. He's a photography enthusiast and he did confirm that lower power binos (and most other optics) should have a greater depth of field, all other things being equal. He couldn't say that the 8x Athlons would have just as much depth of field as the 8x Meoptas, but he did seem pretty confident they would be better in that regard than the 10x Athlon. He said to send them back if I wasn't happy with them, so I went ahead and placed an order.

BTW, if you ever get Neil on the phone, ask him to tell you the story about the time he told his wife he was going out to have lunch with his old stripper girlfriend - just to catch up, you understand...

You're the man, Neil!

 

[rhsc]

Just a follow-up comment...

The 8x Athlon does have a broader depth of focus than the 10x, but they're not quite as good as the Meopta 8x binos in that regard. Really a tiny advantage there for Meopta, and the Athlon perform better in all other aspects, so I'll be keeping the Athlons. Incidentally, I also have a pair of porro prism Steiner M750r that don't perform much better than the Athlon 8x roof prism, especially in regards to field of view, color rendition and low light performance. Really impressed with these Athlon binos, especially for the price. Camera Land still has them on sale thru Dec. 31 for $199.99.