Binocular focal depth

[Major Dave (retired)]

I use binos mostly while still hunting in dense cover. I find that I can pick apart the cover, looking for a telltale antler tip, an ear, or other small,but revealing parts of a deer.

When using 8X or 10X binos, the focal depth seems to be limited to about 10 yards. But when I tried using a newly acquired 6X bino, the focal depth is as much as 30 to 40 yards. Not near as useful for my purpose, in my opinion.

Is this normal, i.e., high magnification equals shallow focal depth, low magnification equals deep focal depth? Or is it more like $300 binos versus $100 binos?

The distances involved are less than 75 yards in all cases.

Your comments/experiences, please.

 

[wogpotter]

Its a function of magnification, or objective diameter & perfectly normal. The more magnification & the bigger the front lens the less depth you get. It is also related to distance BTW closer = less, & further = more at the same magnification.

The correct term is "depth of field", or more accurately "depth of focus" if you want to Google for all the details.

 

[g.willikers]

Same with camera lenses.
Wide angle, low magnification, lenses have greater depth of field.