Binoculars.org

Zoom binoculars have a major advantage over standard binoculars, the ability to change or modify the magnification, however there are some disadvantages you need to understand when selecting a zoom binocular.

For example, a 10×50 binocular has 10x magnification with a 50mm objective lens.  It’s exit pupil is measured at 5mm.  With the nice large 50mm objective lens it can gather a lot of light.  The 10x magnification is a nice all-around power for most uses. 

But now you have seen binoculars with zoom ability such as 10-22×50.  Meaning they have magnification that can “zoom” anywhere between 10x and 22x.  But what many binocular shoppers forget is that the objective lens stays the same, the 50mm objective lens can not change.  So your exit pupil at 22x is only 2.2mm, giving you a much dimmer image.

Zoom binoculars are great, but what must be remembered is that they will have very dim images at the highest of magnification powers.  I like to use the example of your home stereo volume knob – it may go to 50 but you always listed to it at 15 or 20, maybe 25 if your being really loud.  Anything over that usually distorts and does not sound good.  Its very similar with zoom binoculars.

I won’t say all zoom binoculars are bad, or that they are a poor choice – but what I will suggest is that you consider the use of your binocular.  For birding, a 8x or 10x binocular is most preferred.  So you may never use the higher power, lower quality images. 

Zoom binoculars have a great benefit, they have the ability to get in extra close if you need it.  But that extra magnification comes with a con – poor image quality and dim images.  Food for thought when thinking of getting a zoom binocular.

My advice:  If a zoom binocular that you like costs 150$, I bet there is a standard fixed power binocular priced very close.  I bet 9.9 out of 10 times that the similar priced fixed power binocular will be higher quality.