Part of photography's appeal is how it can combine history and journalism with aesthetics. Photographs also tend to be somewhat less pricey to collect than paintings or prints.

Aperture

www.aperture.org
Site Founded: 1997 (online gallery opened in 2003).
The Art: Aperture is the granddaddy of art-photography magazines, founded in 1952 by Ansel Adams and other giants of the genre. Its website has prints by the old greats, such as Paul Strand and Edward Weston, and contemporary superstars, like Annie Leibovitz and Sebastiao Salgado.
Price Range: 350 to more than $3,500 (most are well under $2,000).
Return Policy: Seven days.
The Site: It offered by far the easiest, clearest, and best shopping experience of the photography sites testers visited. Search by photographer's name, title, or time period — or click on "Affordable Prints" to browse through works under $500.

Photo Eye

www.photoeye.com
Site Founded: 1996 (gallery opened in 1991 in Santa Fe; originally in 1979 in Austin, Texas).
The Art: Mostly black-and-white works from the gallery, as well as some pieces signed by photojournalists from the famous Magnum studio.
Price Range: $200 to $4,000.
Return Policy: 10 days.
The Site: Search by name, genre, camera format, print process, or keyword. Two potential annoyances: You'll have to e-mail the gallery for some prices, and Photo Eye special-orders certain items, possibly tacking several days onto the delivery time.

Eyestorm

www.eyestorm.com
Site Founded: 1999.
The Art: This British site's huge selection spans arty abstractions, nudes, celebrity portraits, and celebrity photographers (a Dennis Hopper portrait of Andy Warhol, anyone?). There's much more color photography than on the Aperture site, including signed Helmut Newton lithographs and marvelous art prints. For works by emerging British artists, click on the link to its sister site, www.britart.com.
Price Range: $700 to more than $86,000.
Return Policy: 28 days.
The Site: It moves quickly, with many images on each page. If you don’t like a price, select "Make an Offer" and try your luck. When Real Simple’s order was running late, Eyestorm had it delivered by messenger to make up time.

Shown: Bastienne's Eye, by Ralph Gibson, 6 by 9 inches (unframed), $1,120, from Eyestorm.