You can still spend two or three times as much for a digital camera, but $500 these days will get you a lot -- in particular, 4 megapixels of resolution, enough to allow a sharp 8-by-10 print even after cropping. That, in turn, means that you could use a digital camera as your only camera.

We tried out three 4-megapixel models, all with $499 list prices: Hewlett-Packard's Photosmart 850, Nikon's Coolpix 4300 and Olympus's C-4000 Zoom.

The HP 850 is the hands-down winner for pure optical horsepower, with an 8x zoom lens that offers more than twice the reach of the Nikon and Olympus 3x zooms. (HP also includes 7x digital zoom, for 56x total zoom, but at that level the results are grainy and blurred unless you mount the camera on a solidly planted tripod.) The 850 is also the only camera of the three to employ a camcorder-style electronic viewfinder. It shows all of the image, rather than the 80 or 90 percent of optical viewfinders.

The 850 is the heaviest of the three, weighing 17.7 ounces with four (short-lived) AA batteries. It's quick at daylight shots, but in darker conditions it takes as long as two seconds to go from focus to click; it's a bit clunky to use overall. It uses SD/MMC memory cards, the same kind used by quite a few handheld organizers and digital music players. The infrared focus combined with the 8x zoom for excellent results, but at full zoom we got blurry shots without a flash.

The Nikon Coolpix 4300 is the lightweight at 10.2 ounces. It has a contrast-based auto-focus system, which eliminates the annoying red glare before a shot but doesn't work as well in low light. It takes pictures without any detectable lag. It uses cheap CompactFlash memory and, unlike the HP and Olympus cameras, includes a rechargeable, long-lasting lithium-ion battery. The 4000 also sticks with Nikon's scene-selection system, which offers a variety of pre-set focus and exposure options, such "party," "portrait," "sunset" and even "museum" (it turns off the flash).

The Olympus C-4000Z is the middleweight at 13.4 ounces with four AA batteries or two costly rechargeables. The look-alike of earlier Olympus models has a 3x optical zoom, plus digital zoom that combines for a 10x capability. That usually means little in practice, but Olympus's digital zoom really did feel seamless, and in-camera processing produced quite good results.

The 4000 includes the same infrared focusing as the HP, so low-light focus was usually on the mark. The shutter lag was less than a second. But Olympus left out the nifty wireless remote control it includes with other models. In addition the 4000 uses SmartMedia memory cards, which have been declining in popularity and can store no more than 128 megabytes.

All three cameras are bargains among current offerings (list prices of Canon's and Sony's 4-megapixel models, for instance, remain well above $500). They all have both automatic and manual modes, allowing users to set ISO speed, choose aperture-priority or shutter-priority modes, set white balance, and switch metering between average, center-weighted and spot. The Nikon and Olympus also let you save groups of manual settings. All three offer the usual movie mode, with the usual weak results. And all three connect via USB to a Windows or Mac computer.

The HP 850 is the choice for big-zoom, big-camera lovers, but it's a lot to take with you everywhere. The Olympus 4000 is a good overall camera, but missing the extras of its pricier siblings and stuck with a poor choice of memory. The Nikon 4300 is much smaller and lighter than the HP, with faster and easier operation and equivalent picture quality up to the 3x zoom range. As one who packs a single carry-on for travel, I would choose the Nikon.

Buyers on a budget, however, might do better by spending still less. The digital-camera market abounds with good deals at lower, still usable resolutions -- 2 megapixels for $200, or 3 megapixels for $300. And it's only going to get better -- which can make it hard to decide on a camera now.