One of the biggest trends at this year's PhotoPlus Expo in New York City last week was the increasing popularity of small digital cameras with oversized imaging sensors.

At Sigma's booth, there was last year's pioneering DP1 alongside the more recent DP2, both equipped with Foveon chips and fixed focal length lenses. Olympus, of course, was showing off its slick-looking EP-1, which uses a Micro Four Thirds imaging sensor and specially designed interchangeable lenses.

And then there was Leica's booth, which was overrun with photographers looking to touch and try the new $7,000 M9, which shoehorns a full-frame sensor into a classic rangefinder camera body. Photographers were also itching to play with the brand new Leica X1, which is the German company's first foray into creating a truly compact camera with a digital SLR-sized imaging sensor.

Noticeably absent from PhotoPlus this year was Panasonic, which just last month announced the Lumix GF1, a compact camera with a Micro Four Thirds sensor that's very much like the Olympus EP-1. While Panasonic GF1s may have been missing from the show floor—where's the pro love Panasonic?—the camera's name was definitely on photographers' lips when doing comparison shopping.

Rocky Start

Despite the hype over these new small cameras with big sensors, the technology has had something of a rocky start so far. Both Sigma's DP1 and DP2 have received mixed to poor reviews in the last year while feedback on the Olympus EP-1 has ranged from adoration over its stainless steel retro design to disappointment over its slow autofocus and inconsistent image quality.

Though preliminary reviews on the Leica M9 have been quite positive—look for my take on the camera in the upcoming November issue—the M9 is a bit of an anomaly because of its high price and stubborn rangefinder traditionalism. (Only manual focus and lens-based aperture adjustment.)

Since the Leica X1 will not be out until early next year and Panasonic GF1 test units are extremely hard to come by, the jury is still out on both of those cameras.

From the get-go though, manufacturers have tried to tout these pocket rockets as offering the same photographic experience as a DSLR but at less than half the size and weight. If they have not quite lived up to this promise, it just proves that the engineering behind these cameras is much more challenging than it may have first seemed.

In the days leading up to PhotoPlus, I talked to representatives from Sigma, Olympus and Leica to find out what was so tough about putting a large image sensor into a small camera body and discussed what they saw for the future of this burgeoning new product category.