Some camera binoculars look much like regular H-shaped roof-prism binoculars, with the addition of a camera lens and LCD screen set between the two lens barrels. Other camera binoculars are chunkier and more block-like, although users say these are still comfortable to use. However, the addition of the camera lens generally makes these heavier than regular binoculars.
The two numbers in the camera-binocular name -- the magnification and aperture numbers -- refer only to the binoculars, not always to the camera. The first number tells you how close you'll be able to see. In a specification of "8x32," for example, the "8" means that the binoculars make an object look eight times as close as it is. The number "32" means that the lens furthest from your eyes -- called the aperture or objective lens -- is 32mm in diameter.
Like regular binoculars, the best camera binoculars use Bak-4 prism glass rather than Bak-7, and they use fully multicoated (FMC) lenses -- several layers of special coatings on both sides of even the internal lenses. Lens coatings minimize the inevitable color distortion and loss of light that occurs when light passes through glass.
The camera part of digital-camera binoculars has its own specifications. The number of megapixels describes the resolution of the camera sensor. The lowest-resolution cameras have VGA resolution of 640x480 pixels. These images aren't detailed enough for anything other than e-mailing, posting on a website or the occasional small print. 1-megapixel and 2-megapixel camera binoculars can print a decent 4x6-inch photo. Some camera binoculars -- especially by Celestron and Meade/Simmons -- advertise a higher resolution achieved by 'interpolation,' which means that the camera tries to enhance the image quality electronically. Reviews say you should ignore these 'interpolation' numbers, since the results tend to be less sharp. The true sensor resolution is what counts.
Most camera binoculars with both PC and Mac computers and use internal flash memory to record images, and some have card slots that allow you to expand the memory. All run on AA or AAA batteries.
The biggest hurdle to taking sharp pictures with camera binoculars is that the camera focuses much further away than the binoculars -- a disconcerting aspect which is the basis for many complaints. This means that you may have an image in sharp view in the binoculars -- 15 feet away, perhaps -- but the camera can focus only as close as 30 feet (or 50 feet for some models). This discrepancy accounts for some of the irate postings in user reviews at Amazon.com and Epinions, where people complain that it's impossible to take a photo that's not blurry. Except for the expensive Bushnell Instant Replay 8x32 (*est. $380), camera binoculars are really intended only for photographing objects that are quite far away.
Instant-replay video is the most attractive feature of camera binoculars. When in video mode, the camera binoculars constantly save temporary video in a memory cache -- then at any point, you can choose to save the last 5 to 60 seconds of video to permanent memory. In other words, you can run the video camera while looking through the binoculars, then stop and save the last few seconds. In the New York Times review, David Pogue says "What's so smart about the idea is that it perfectly suits the kinds of situations for which you use binoculars. Waiting for that dark-eyed junco to emerge from its hole? Instant Replay throws away all the boring waiting-around footage and retains only the magic moment. Tracking your child on the soccer field? Tap the button to retain only the goal-making part."