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Binocular specifications

posted by Jerry Liguori at
on Sunday, October 16, 2011 

Some birders get confused on what the numbers on their binoculars stand for. For example 7x45 (pictured above, best binoculars in the world)...the 7 stands for the magnification (power), and is built into the ocular lenses (the lens you put your eyes up to). The 45 stands for the diameter in millimeters of the objective lens (wider lenses at the end of the binoculars). The wider the objective lens, the more light they are supposed to gather, although glass quality and type of coating on the lenses plays a part in this.

The field of view is not determined from the size of the objective lens...the field of view is determined by the width of the ocular lenses. So a 7x50 binocular does not necessarily have a wider field of view than a 7x42...and may not be brighter in some cases. The field of view is measured in feet per 1000 yards. So a FOV of 350 ft. at 1000 yds. will be smaller than a FOV of 405 ft. at 1000 yds. When comparing full-sized high quality binoculars, most 10x binoculars have a smaller FOV compared to 7x binoculars. Don't be convinced by someone who claims to own a 10x binocular with a wide FOV.


Blogger Tim Avery said...

Jerry, great informational post. Now off to get some 12X50s so I can see the crap out of some of those birds...

J/K, of course, I know you love those Zeiss, and they are some supremely amazing optics. I used 10x42 Nikons for about 9 or 10 years before finally sizing down to 8x42s--and I wouldn't go back.

More powerful magnification does not equal better looks at birds, especially when you consider the weight of the binoculars, the mount of light let in, and the ease of getting the bird in the field of view!

October 17, 2011 at 9:35 AM  
Blogger Stephanie Greenwood said...

Thanks for this article and the interesting tips! I've always wondered what kind of binoculars I should get. Is it overkill to carry binoculars and a 400 mm lens on a camera? I've done it before and I find it hard to juggle between the camera, where I'm going back and forth between my viewfinder and my "bare eyes" which actually aren't bare because I wear glasses, and then my binoculars where I have to take my glasses off. So, the protocol would be, look through the viewfinder of the camera, look with my eyes, take off my glasses, adjust focus on binoculars...and then view the birds if they're still there after all that. Are there any good binoculars that don't require you to take off your glasses? And can you adequately bird with just a camera? I'm probably going to upgrade my body now that I have the big lens...from a Nikon D40X to a Nikon D300s, which has an LCD preview screen (with the D40X the picture only shows up on the LCD screen AFTER you've taken it, so everything has do be done squinting through the viewfinder, which can be taxing when you're tracking the movement of a bird) so hopefully that will make things easier.

October 17, 2011 at 9:48 AM  
Blogger Tim Avery said...

@Stephanie: for birding nothing beats binoculars. Using photo equipemnt to ID birds leads to a lot of problems as it is only a snapshot of the bird. It doesn't tell you as much as watching the bird, seeing it move, seeing how it acts, and being able to study it before it's gone. I try to keep my camera on my shoulder until I have ID'd something, or until I am stumped and need photos to study it further, or to help be sure of the ID later.

I would never trade my binoculars in solely to use a camera as it just isn't the ideal tool for identifying birds while birding.

October 17, 2011 at 9:54 AM  
Blogger Kiirsi said...

@Stephanie: at Tim's great advice, I saved money for a while and bought a set of Nikon Monarch 8x42's. I wear glasses and with this particular binocular, I don't have to take my glasses off. People who don't wear glasses have to twist the eyecups out for their eyes. I think they're great!

October 17, 2011 at 10:18 AM  
Anonymous Jerry said...

There are lots of models that work well with glasses. I wear glasses.

I'm glad this short post got a few responses.

October 17, 2011 at 6:20 PM  
Blogger Vic Berardi said...

Jerry, is there a pair you would recommend from current models? I've been using the Nikon 10 X 42 Superior E and Swarovski 10 X 42 but would like to sell the Swarovskis and get something in the 8 power range. I've been looking at the Zeiss 8 X 56 Victory.

By the way, those binos of yours should go into the birding hall of fame one day!

October 18, 2011 at 7:31 PM  
Anonymous Jerry said...

"birding hall of fame"....Vic, you're killing me.

All the full-size Zeiss 7x and 8x are nice. You know what you like. $ is the real factor, and some of the binoculars out there today are pricey and not worth the cost.

October 18, 2011 at 7:53 PM  
Anonymous Jerry Liguori said...

You are welcome

February 26, 2014 at 10:20 AM  
Anonymous Koller said...

Finally a good input I've found here about binocular specifications. Its my real pleasure that I've stopped by here and come to know some pretty vital information about the specification of binocular and I'm pretty much sure that here provided information will be handy for everyone. Keep up the good work :)

February 26, 2014 at 11:05 AM  
Anonymous Jerry Liguori said...

Hi Koller

Happy you found it helpful!

February 26, 2014 at 11:19 AM  
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August 22, 2020 at 9:38 AM  
Anonymous Carl Aldred said...

Thanks for your great informative article. I travel in the jungle and I want to get out a binocular of my pocket-size. Can you tell me which one is best for me?

September 4, 2020 at 7:26 AM  

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