Pentax 8x25 UCF X

Typically, we don’t review mini binoculars because the optical quality is such that they are not good alternatives for birding. There are circumstances where mini-binoculars are better suited than full-sized binoculars. Mini binoculars make great second binoculars, for tucking into the glove compartment, stuffing into a backpack, or carrying when traveling on non-birding trips (admit it – we never really go anywhere without at least some binoculars!). Mini binoculars are also ideal for children who cannot hold heavier binoculars steady enough, and they double up with other uses, at the opera or sporting events. So there are a lot of reasons a birder might own a pair of mini binoculars.

How well does the Pentax 8x25 UCF X stand up in a birding binocular review? Like many mini binoculars, these are of the reverse porro prism design (see the Basics I article in the “All About Optics” section). As such, they cannot be sealed, nitrogen-purged, waterproof and so on. But this doesn’t mean poor optical performance. This binocular features BaK4 glass prisms, and multi-coatings for best light transmission and minimal distortion. This helps to compensate for the smaller objective lenses, which gather less light than a full-size binocular will. The field of view at 1000 yards is a modest 324 ft, which would be only average performance for a full-size 8x binocular, but is actually pretty good for mini binoculars, which typically have recessed objective lenses like the UCF X does.

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Eye relief is 15 mm, again short by full-size binocular standards, but fairly typical of mini binoculars. The eyecups pull straight out, and they have a detent stop in the middle, allowing an intermediate position selection. They showed no tendency toward inadvertent collapse during use. The diopter adjustment is handled by a unique mechanism: a spring-loaded dial located in the hinge region. Similar to a radio knob, pressing on it causes it to be popped out, where it can be adjusted by twisting in either direction. Depressing the knob a second time causes it to lock in the selected position. The placement of this knob has consequences in the design: the central hinge region can’t accommodate the hinge itself! Pentax has solved this with an elegant design: each of the oculars hinges separately to the central core of the binocular. Moving either “wing” causes the other to move equally.

The minimum focal distance on this little binocular is a impressive 6.2 feet, which is better than average for binoculars in general. Compensating for this advantage is the focal mechanism itself. There is a small, hard-plastic, centrally located knob, which adjusts in a very shallow mechanism: it takes a full 3 turns to go from minimum close focus to infinity. Moreover, the knob is deeply recessed into the body of the binocular, forcing one to make this adjustment in small installments. This is a very slow focusing mechanism for birding applications.

The body is encased in black rubber housing that is slick to the touch. The ocular “wings” have shallow thumb grooves, as does the bridge structure between them. The weight of this assembly is a feather light 10.6 oz. Carrying this binocular won’t tire out even the feeblest of birders! This renders the tripod attachment site on the underside of the body somewhat incongruous. The thin nylon web strap attaches to gimbaled plastic brackets up on the oculars. This mechanism works fairly well at keeping the strap attachment point out from under the hands. The lens caps fit very tightly over the oculars preventing accidental dislodging. There are no lens caps for the recessed objective lenses. Also included is a padded black leather case. The strap fits out the sides of the Velcro-closing flap so that binocular and case can be worn over the neck. The case also features a belt-mounting loop on the back for convenient deployment at the waist.

So when all is said and done, how does the Pentax 8x25 UCF X stand up? As noted above, reverse-porro prism mini binoculars have limited applications for the serious birder, but there are applications for them. If you want a pair of high-performance, lightweight binoculars, the UCF X is a strong contender, and we give it a solid thumbs up.

Check out the New Pentax UCF X II - current price and availability