Barska Gladiator 7-21x40 Review
The Barska Gladiator 7-21x40 (starting at $30, Amazon) features a zoom lens that closes in on the objects you see far away along with a wide objective lens that should let in enough light for night viewing. In fact, a Barska Gladiator 7-21x40 review at Amazon reports that parent and child use it for everything from covertly observing cats to getting a close look at the moon. However, a review at Optics Planet asserts that the variable magnification from 7x up to 21x is better in theory than in practice. The field of vision is diminished below a magnification of 10x, and anything above a magnification of 14x looks blurry. Several binocular reviews posted at Amazon further gripe that the focus mechanism is too loose, that misaligned optics produce double images, and heavy anti-glare coating on the lens reduces the light needed for proper viewing.
The Barska Gladiator 7-21x40 features a roof prism with BK-7 glass and a center focus that includes a thumb lever for zooming. The field of view changes with the magnification you're using, but is 261 feet at its lowest (7x) magnification; at this level you're better off focusing on an object and not the field around it. Eye relief at 7x magnification is 14mm - a good distance for eyeglass wearers. The Gladiator 7-21x40 features a Porro prism with BK-7 glass and at 27.9 ounces, it's a bit on the heavy side (there is a tripod mount).
The zoom and variable magnification feature holds out the promise of wide-ranging viewing opportunities. But if that freedom is what you want in a pair of binoculars, this model may not get you there.