A pocket-sized digital camera that can produce image quality on par with a digital SLR has been something of a Holy Grail for street photographers. In recent months several notable contenders have come to the throne, including the Canon G9 and the Ricoh GX100, both of which I've mentioned in brief in my Objects of Desire column for PDN.

What both of those cameras lack when compared to professional-level DSLRs—in my estimation and in the views of most of the other reviewers out there—is the ability to produce low-noise images in low light at high ISOs. The problem is simple physics: When you are using an imaging sensor the size of a fingernail and pumping it full of megapixels (12 mp for the Canon G9 and 10 mp for the Ricoh GX100) those individual pixels are going to be extremely small.

Smaller pixels means the imaging sensor has less light to work with, which can result in the occasional misfire, thus producing noise. Though I've recently detected a small movement afoot in the digital photography community to embrace noise—with some even comparing it favorably to "grain" in film—I have to respectfully disagree with this notion. The thing I hate most about noise in digital cameras is not those annoying little dots of color themselves, but rather how much they muddy up an image.

I recently did a comparison test for a consumer electronics magazine of some of the latest point-and-shoot cameras on the market—most of which had at least 10-mp sensors—and I had a hard time getting any of my shots to look sharp at ISO 400 or higher. Despite the presence of gimmicky features such as Smile Detection and touchscreens, many consumer point-and-shoot digital cameras seem like they've taken a step backward in terms of image quality. As far as noise goes, I'm afraid pro-friendly compact cameras such as the G9 and GX100 also seem to be stuck in the mud.

JUST MAKE IT BIGGER, RIGHT?
The solution to this issue would seem, on paper, to be an easy one. Put a bigger sensor into a compact camera without boosting the resolution and you'll be able to capture cleaner, sharper images without having to lug around a digital SLR.

Sounds simple, yes, but it's obviously not. Just ask the designers and engineers behind the Sigma DP1, a compact camera with a DSLR-sized sensor that was fraught with so many delays that some reviewers—including yours truly—were starting to write it off as so much vaporware. (I actually think I also grumpily compared it to the mythical Sasquatch in PDN's blog but I might have accidentally switched to decaf on that day.)

In March, Sigma proved the naysayers wrong when it started shipping the DP1, a camera first shown as a prototype way back at Photokina 2006. That's a long time between unveiling and release, considering that nothing major has changed since the initial announcement. Why the delay? I'm sure there were many late nights spent at Sigma headquarters trying to fit the veritable square peg of a big sensor into the round hole of a compact camera while still leaving room for a quality lens.

Whereas most consumer compact cameras use a sensor with a diagonal size of 7.7mm, higher-end "digicams," such as the Canon G9, use a sensor about 9.5mm diagonal. In contrast, the Sigma DP1 uses an APS-C-sized sensor with a diagonal size of approximately 25mm. Overall, the DP1's sensor is 20.7mm (w) x 13.8mm (h) with individual pixels sized at about 7.8 microns. As a point of comparison, pixel size on the Canon 40D, a popular mid-level DSLR with an APS-C sized sensor, is a fraction smaller at 5.8 microns.

The one tricky thing about the DP1's sensor (which I will purposely avoid going into in depth because of the can of worms attached to it) is that like the Sigma SD14 digital SLR, it uses a Foveon X3 CMOS image sensor instead of a typical CMOS or CCD sensor.

Without getting into too many specifics—and if you read this magazine or this column regularly you likely know most of them already—a Foveon X3 sensor is designed to mimic the look of film by directly capturing three layers of red, green and blue light at each point in an image during exposure. A "Bayer-pattern" sensor, such as a typical CMOS or a CCD captures red, green and blue separately at different photo sites, which are then reconstructed through interpolation to create color.

While Foveon X3 sensors and the Sigma cameras that use them have a small but devoted following, they're not without their controversies. In particular, there hasn't been much agreement on how to rate resolution on these unique sensor sandwiches. Foveon and Sigma triple the amount of pixels on their chips—because of the three layers—making a camera such as the DP1 and the SD14, which technically have a resolution of 4.6 megapixels, into approximately 14-megapixel cameras.

While some people just insist on describing these Sigmas as 4.6-megapixel cameras, they are in the minority. Most of the conventional wisdom is that the sensor in the DP1 and SD14 can capture about as much resolution as a comparable 8- or 10-megapixel camera and I'm with them on that.

But whatever. I find nitpicking about resolution when it crosses the 8-10 megapixel range to be just that: nitpicking. I've been able to produce perfectly good prints at 13 x 19-inches and above with 10-mp cameras as I have lousy prints. It all comes down to noise and sharpness, which is what the Sigma DP1 was designed to address.

DIGICAM IN A TUX
To say that the design of the DP1 is conservative is an understatement. This all-black, rectangle-shaped camera doesn't mess much with the rangefinder-like style of similar-tier models, such as the Canon G9 and Ricoh GX100. Of the three, I prefer the style of the DP1 for its classy simplicity—it looks like a digital camera in a tux. (If you're the sort of person who prefers your cameras to appear like they stepped off the deck of the Starship Enterprise, you'll probably find the DP1 rather boring.)

You can get several accessories for the DP1 that don't exactly "pimp it out" but do add some versatility to a camera that does little aside from capturing images and basic video clips. Though the Sigma VF-11 Viewfinder ($149.95), which attaches to the hotshoe of the DP1, is kind of cute and helps you frame your shots in bright light when the camera's LCD washes out, I abandoned it after a day of shooting because I realized I was doing fine without it. (Plus, I kept getting fingerprints on the front and rear glass.) Unless you're really attached to optical viewfinders, I'd say skip it and save your money.

Also nice but somewhat unnecessary is the Sigma HA-11 Hood Adapter ($17.95) which functions as a lens hood to prevent flare, while also serving as a 46mm filter mount for adding effects filters and lens accessories. Finally, there's a miniature EF-140 DG electronic flash ($79) that sure beats the weak pop-up flash on the camera, but defeats the "special purpose" of this camera, which is to shoot clean images in low-light without a flash.

NO FRILLS
Slightly heavier than your average compact digital camera at about nine ounces, the DP1 is well balanced and feels good in your hand. The camera is solidly built—a tough combination of metal and polycarbonate. A grid of small bumps on the front of the DP1, though subtle, does provide some extra grip for your fingers. Practically speaking, I would have preferred more of a raised handgrip on the DP1 like the one on the G9 and the GX100, even though it would have ruined the elegant look of the camera.

On the front of the DP1 is the housing for the 16.6mm (equivalent to 28mm on a 35mm camera), f/4 Sigma lens. Interestingly, even though the lens is a fixed focal length, it extends out like a zoom when the camera is powered on. And the DP1 sure takes its own sweet time to power on and extend its lens—averaging about five seconds in my testing. (A side note: I hated the DP1's lens cap, which doesn't attach to the camera and is tough to mount on the lens.)

I also averaged an extra two seconds until you can actually lock in focus—the DP1 uses nine focusing points that are manually selectable—and take a picture. That is surprisingly slow, but stays in line with DP1's overall sluggish performance. In continuous shooting mode, the DP1 averaged 3 frames per second—which is about normal for a camera in this class—though it would lock up for about 15-20 seconds after each 3fps burst as the RAW files were transferred from the DP1's internal buffer to the card.

If ever a camera cried out for a firmware update to increase its speed it would be this one. As of this review, however, it had not emerged.

In addition to autofocus, the camera has a somewhat crude (though effective) manual focus option that involves turning a dial on the camera body until you get a sharp image. You can also digitally magnify your image in this mode to make sure you have it as sharp as you want it.

Though I got excellent results with the 16.6mm f/4 lens on the DP1, it definitely has its limitations. Along with its inability to zoom, there's no Macro mode and the closest I could get the camera to focus from was about 30cm away which involved switching to the "Full" focus mode. The DP1 also doesn't have any sort of image stabilizer, a feature that has become de rigueur on most digital cameras.

I liked the camera's 2.5-inch LCD (230,000 pixels), which produced sharp, accurate image playback. The camera's menu system is pretty straightforward, but is noticeably slow to navigate through. (Big surprise, right?) Mode options are pretty basic, including Program, Aperture Priority, Shutter Priority and Manual, along with an unimpressive (320 x 240 at 30 fps) video mode that seems thrown in as an afterthought. There's also a mode for recording audio clips that I cared even less about than the video mode.

Metering modes are pretty basic too, with Evaluative, Center Weighted and Spot Metering.

BUT WHAT ABOUT PICTURE QUALITY?
Yes, if you're considering the Sigma DP1, you probably don't give a damn about what kind of video mode it has. This camera—which isn't cheap at $799—is built for taking pictures and image quality was near the best I've seen for a digital camera its size. If it wasn't as good as a mid-level DSLR such as a Nikon D300 or Canon 40D, it came close to entry-level DSLRs such as the Rebel XSi and Nikon D60, with low noise, good color and excellent sharpness.

As stated before, though, it's not fast, especially in RAW mode, which is the way you're going to want to use this camera. Along with being slow to start up and capture a first shot, shutter lag was noticeable—mostly because of the slow autofocus—while shot- to-shot speed was deplorable with the camera taking a full eight seconds between pictures. (It should be noted that I was using a fast San Disk Extreme III 1 gb SD card during my testing.)

There was a marked difference not only in recording speed but also in image quality between the RAW files and JPEGs I shot, which is something Sigma is aware of. Upon receiving my sample DP1 unit from Sigma, I was encouraged by a Sigma PR representative to shoot in RAW, which is "the camera's greatest strength." JPEGs, I was told, would improve with "future firmware upgrades." (Interestingly, there is no RAW + JPEG mode for recording both formats simultaneously on the DP1 yet.)

In a series of shots I took of the George Washington Bridge near sundown using the DP1's 12-bit RAW ".X3F" format, I saw very little to no image noise in the long shadow areas the bridge cast over the Hudson River when shooting at ISO 100 and 200. ISO 400 wasn't bad either; though image quality fell off noticeably at the maximum ISO 800 setting, which was a disappointment. (This is an area in which the DP1 trailed entry-level DSLRs I've looked at.) In particular, the DP1 struggled with nasty purple noise in areas with lots of dark browns, making my late-afternoon shots of a grove of trees look splotchy.

So while the Sigma DP1 might not be the ideal lowlight shooter that street photographers have been looking for, images shot at ISO 400 and lower were much cleaner than anything I've seen from competing models. Shots at ISO 100 were beautiful.

Even though there was neither image stabilization nor any focal range, my photos were extremely sharp, thanks to the quality lens. I also liked the almost- three-dimensional quality I continue to get from Sigma cameras that use Foveon image sensors. (This is, perhaps, part of the Foveon mystique—but something I've actually experienced in my photography.)

The one area in which the camera did struggle was in providing the necessary resolution for large prints. Call it a 14-megapixel sensor or a 4.6-megapixel sensor, but either way I noticed a significant drop-off in detail in 13 x 19-inch prints I made from DP1 images.

It should also be noted that reviewing and editing X3F RAW files in Sigma Photo Pro 3.2 was a painfully slow process. Though I found the program to be a robust editor, it was a huge memory hog that is sure to drive you crazy if you plan to shoot and edit any big jobs with the DP1. As of this writing, no update existed to read the X3F RAW files in Adobe Camera RAW/Photoshop, however, by the time this review is out that will have been corrected.

THE BOTTOM LINE
Despite some serious deficiencies including its annoyingly slow overall speed, limited fixed focal length lens, and less-than-stellar ISO 800 performance, I can't help but get excited by the Sigma DP1. Though in the past some have questioned Sigma's claims of being able to produce "next generation" cameras (including, I must admit, myself), with the DP1 they have delivered exactly what they promised. Here's a compact camera with a DSLR-sized sensor that can produce some kickass pictures. Here's a camera you can pull out inconspicuously to beautifully capture a decisive moment (if it's a slow-moving one). Here's a camera that's not likely to draw a crowd when you use it but should turn heads when you show off the high-quality pictures it produces.

Though it's far from perfect, the DP1 is a significant step forward in the quest for the ideal compact camera. Street photographers may have just found their new best friend.

Sigma DP1

www.sigmaphoto.com

Pros: Best image quality we've seen from a compact camera at ISO 400 and below; very sharp, high-quality lens; simple, elegant design; durable, well-balanced camera body.

Cons: Annoyingly slow overall speed; limited fixed focal length lens; no image stabilization; ISO 800 images were noisier than we expected; Sigma Pro Photo software is very slow; few extras for the high price.

Price: $799