It seems like a no-brainer: Since digital camcorders and digital still cameras use the same kind of electronic sensor to record images, why not build a single device that does both really well?

Like many ideas that seem simple on the surface, the devil is in the details. It’s actually almost impossible, for now at least, to design a sensor that delivers outstanding performance both ways.

The result, which I’ve seen over and over in recent years, are digital camcorders that take bad still pictures and digital still cameras that shoot bad video.

Samsung has finally delivered the best of both worlds with an elegant compromise: the two-eyed SC-D6040 DuoCam at $799 (www.samsungusa.com). The DuoCam has separate lenses and sensors for video and stills, one on top of the other. A color electronic viewfinder and swing-out 2.5-inch color LCD panel are shared for shooting and playback.

The DuoCam is no bigger than the average palm-sized camcorder and weighs a relatively svelte 1.1 pounds, yet it offers the full feature set you’d get from lugging around both a camcorder and a digital camera.

You do pay for this all-in-one convenience; a roughly equivalent camcorder and still camera purchased separately would cost about $200 less. But, after several days of shooting video and stills, I can recommend the DuoCam to anyone who wants to regularly switch between the two and doesn’t mind spending more for the privilege.

Here are the details, from the bottom up:

The lower half of the DuoCam’s front is the digital still camera, with a four-megapixel CCD sensor and a 3X optical zoom lens. There’s a pop-up flash on top of the unit, and a slot for inserting either Secure Digital or Memory Stick cards for storing pictures. Photo enthusiasts get some advanced features, including manual focus and manual white balance.

The top half is the camcorder, with a 680,000 pixel CCD – sufficient resolution for digital video – and a 10X optical zoom lens. Video is recorded on standard Mini DV cassettes. Advanced features include an infrared light for shooting in the dark and digital image stabilization.

A dial switch at the back, on the right side, moves the DuoCam between camcorder and still camera mode. You can use either the electronic viewfinder or the LCD screen to frame video and stills. The slider switch for zooming between wide angle and telephoto controls the top lens in camcorder mode and the lower lens in still camera mode.

As you can tell from this description, if you’ve ever used a camcorder, the DuoCam looks and operates more like a camcorder than a digital still camera. Anyone familiar with conventional digital still cameras will need some practice to get comfortable using the DuoCam for shooting stills. But the quality of the stills is comparable to other 4-megapixel cameras I’ve used, and the video quality similarly matches other mid-range digital camcorders.

The DuoCam measures 5.4 inches long by 3.6 inches high by 2.5 inches thick. Accessories include a lithium ion battery, an AC adapter, a 16-megabyte Memory Stick card, a remote control and a USB cable for connecting to a computer. There’s also a FireWire port on the camera, also know as 1394 or i.Link, for connecting to computers via FireWire, although you have to purchase a FireWire cable separately.

Samsung is clearly headed in the right direction with the DuoCam. The first generation of the product, the DuoCam SCD-5000 introduced in summer 2003, used an awkward swivel design to rotate the lenses for video and stills into position. The SCD-5000 was a third bigger and heavier than the SCD-6040, which shipped in August, and cost about $400 more.

I spoke with a Samsung product manager last week who told me the DuoCam will get even better in its third generation. The next DuoCam, presumably due in summer 2005, will be only 60 percent the size of the SCD-6040 and could cost even less.

Does this mean the distinction between digital camcorders and still cameras will gradually fade away, leaving us with a single product class of camera/camcorders?

Yes, although not right away.

Today’s image sensors are optimized to work either for video or stills, which is why they don’t do well on the flip side and is why the DuoCam has two sensors. However, engineering improvements now in the works should make it possible to produce sensors that offer both the high resolution required for stills and the fast response time required for video.

Another change just over the horizon is digital cameras and camcorders that store images on small hard drives instead of tape or memory cards. Hard drives work equally well at storing video or stills, eliminating the need for two types of storage, as with the DuoCam using DV tape for video and memory cards for stills.