Bushnell PowerView 10x25mm Roof Prism Binoculars (Black) Expired

The 8x21 are brighter. Exit pupil for the 10x25 = 25/10 = 2.5mm Exit pupil for the 8x21 = 21/8 = 2.6mm. 2.6 > 2.5 so the 8x21 are slightly brighter.

Roof prism designs like these require a phase-correction coating to prevent loss of contrast. According to Bushnell's site, these don't have them (not surprising at this price point). It's hard to argue with them at this price, but if you don't need them right now, a cheap pair of porro prism binoculars should have a clearer, higher contrast image than these. Problem being there isn't a deal for cheap porro prism binoculars at the moment.

That said, roof prism designs are more rugged (optics don't go out of alignment as easily from being knocked around). Lemme cut and paste my writeup about what all the specs mean.


10x is close to the limit of hand-holdability before the image becomes too shaky. For casual handheld use, you want to stick to 7x or 8x.
25mm (or 21mm for the 8x) is the diameter of the front optic. This only indirectly affects image brightness.
25mm / 10x = 2.5mm which is the exit pupil. The bigger the exit pupil, the brighter the image, up to the size of your eye's pupil (about 7mm at night, 3-4mm in day). It also determines the width of the cone of light exiting the binos. The smaller the exit pupil, the narrower this cone, and the more precisely you need to hold the binos directly in front of your eyes to see an image. Important if you're viewing from a moving platform (whale watching) or for comfort if you're viewing for a long time.
Eye relief is the length of the cone of light exiting the binos. The longer the eye relief, the further you can hold the binos from your eyes and still see an image. Mainly important if you wear glasses and don't want to take them off when viewing. You'll need about 18mm+ eye relief to use them with glasses on, although they can be made to work with as little as 14mm. Bushnell lists the eye relief as 10mm for the 8x21, 9mm for the 10x25, which is very short. So glasses wearers will have to take your glasses off to use these.
The short eye relief combined with the small exit pupil will make these uncomfortable to use for a long period of time. You'll have to get your eyes at exactly the sweet spot to see the image. Binoculars with a bigger exit pupil and longer eye relief give you more leeway for your eyes to be away from the sweet spot and still see the image.
Field of view is the width of the image you see through the binos when they're positioned just right. Usually measured as a linear width at 1000 yards away. 400 feet @ 1000 yards is a lot. 200 feet @ 1000 yards is small. FOV diminishes as you move your eyes away from the eyepieces, or as you move them sideways so your eyes are not perfectly centered. Bushnell lists FOV as 378 ft @ 1000 yards for the 8x21, 300 ft @ 1000 yards for the 10x25.
Close focus distance is self-explanatory. It's mostly important for viewing small things which fly away - birds and butterflies. Bushnell lists close focus as 21 ft for both of these, which is rather bad. Good ones can focus closer than 15 ft, some closer than 10 ft.
Neither of these have a screw attachment for tripod mounting.

https://www.bushnell.com/Products...sku=132514
https://www.bushnell.com/Products...sku=132516