Sigma DP2 Merrill: Performance

by Jim Keenan Reads (1,946)
Editor's Rating
6.40

TG Ratings Breakdown

    • Image/Video Quality
    • 9
    • Features
    • 6
    • Design / Ease of Use
    • 5
    • Performance
    • 7
    • Expandability
    • 5
    • Total Score:
    • 6.40
    • Rating 1 to 10, top score 10

PERFORMANCE

With a price tag that would get you into any number of entry-level DSLRs with kit lenses, how does the rest of the DP2’s performance match up with its DSLR-sized sensor?

Shooting Performance

The DP2 loses the startup time race to a DSLR handily, taking about two seconds to display a focus point on the monitor. I was able to power up and get off a first shot in about 3.5 seconds, in the ballpark for the compact digital class. Single shot-to-shot times ran about two seconds. I used a 32GB Lexar 600x speed SDHC memory card for this review, and write times for a single JPEG fine quality, high resolution image ran about 8 seconds. The same shot taken as a high-resolution RAW file took about 13 seconds to write. You don’t have to wait until the preceding image is written to capture another photo as long as there’s room in the camera buffer – the buffer capacity is 7 images in JPEG fine, RAW, or RAW/JPEG quality at the highest resolution. Buffer capacity jumps to 14 images if you downsize to medium resolution.

The DP2 offers 4 frame per second (fps) continuous shooting rates at high resolution, and 5 fps if you drop down to medium resolution, subject to the same 7 and 14 image capacity buffer restrictions. Write time to completely clear the buffer for a 7 burst of RAW files at high resolution took 45 seconds; 33 seconds for JPEG fine. Write times using a 16 GB 400x Lexar card were similar for both single and continuous shooting modes, so it appears you can save a little money by going with a slightly slower card without compromising the camera’s writing performance.

Just as with single shot mode, the DP2 will allow you to continue shooting bursts as soon as there is room for two or more images in the buffer – you can also take a single image once the buffer has room. One drawback with the continuous shooting mode in the DP2 is that there is no continuous autofocus; the camera establishes focus with a first shot of a burst and maintains it for the rest of the burst. If your subject is moving but stays at approximately the same distance from the camera as the initial shot you should have no worries, but subjects moving towards or away from the camera may not stay in sharp focus for the entire sequence.

Sigma DP2 Merrill

Continuous shooting is where the first collateral benefit of mounting a viewfinder on your DP2 comes into play – when shooting in continuous mode the monitor goes blank as you capture the first image and stays that way for the balance of the burst. With the viewfinder attached you’re able to track moving subjects as the monitor blackout does not carry over to the viewfinder.

Whether you’re shooting single frames or continuously, the lack of stabilization in the DP2 takes you back to an age where camera shake was a major factor in images that came out less than tack sharp. Back then we had a rule of thumb for the minimum shutter speed you’d like to use with any particular lens focal length in order to minimize the effect of camera shake during hand-held shooting. The rule is simple and basically stated that you use at least the inverse of the lens focal length as the minimum shutter speed in seconds – for example, if you’re shooting a 25mm lens you would like to have a minimum shutter speed of at least a 1/25 of a second. Shorter shutter speeds are always better where camera shake is in play, and in the case of a DP2 shooting at approximately 45mm in 35mm film equivalents, 1/50 a second would be the minimum you’d try to use. Not surprisingly, the DP2 displays a red camera shake warning on the monitor whenever shutter speeds fall below 1/50 of a second. Here’s the other collateral advantage of having the viewfinder on your DP2 – you’re holding the camera up to your face in order to look through the viewfinder and are able to brace your arms on your sides and also the camera on your forehead, promoting a more stable hold that may allow you to shoot a bit slower than the suggested shutter speed without impacting camera shake.

The DP2 has some other nice features for more advanced users, such as exposure compensation and a three shot auto bracketing capability.

Autofocus times with the DP2 were a mixed bag, generally being fairly quick in good lighting conditions, but even then sometimes hunting a bit if the focus point was centered on a subject that was dark-colored. In dimmer light the DP struggled, a not uncommon occurrence for compact digital cameras- when the camera did acquire focus in dimmer light it tended to be only after it seemingly ran the lens through a range of focus distance. There is no focus assist lamp on the camera. Manual focus is a bit tedious, requiring over a full turn of the focus ring to go from the close focus point to infinity – but the good side of this is it makes fine-tuning the focus easier once you get close to the optimal focus distance.

Shutter performance seemed to show just a tiny bit of lag, but my feeling on this may have been influenced by the timing of the shutter sound accompanying the full push of the shutter button. In any event the DP2 captures the picture fairly promptly when you tell it to.

SIGMA makes an optional flash for the DP2 but we did not have one available for this review. This flash has a maximum guide number of 14m (about 46 feet) at 100 ISO and can be used in Program Auto shooting mode only. In addition to its normal flash setting the flash provides redeye reduction, slow synchronization, and redeye reduction with slow synchronization settings. Flash exposure compensation is also available.

Back in the introduction I mentioned that Sigma provides two lithium-ion batteries with the DP2, but there’s a good reason for this: battery life in the DP2 is short, to say the least. Sigma rates the DP2 as having a 97 image battery life, but in one stretch where I was doing some (but not a lot of) image review and a bit of menu surfing, the battery was exhausted after 72 images were captured. While shooting at Disneyland with minimal image review and shutting off the camera between shots I managed 72 still images and a couple of 15 second videos before my first battery completely drained. About a dozen of the 72 stills were five second exposures in a dim restaurant setting, but suffice it to say you probably cannot have too many batteries along on an all day shooting session with the DP2.

Lens Performance

The 30mm lens on the DP2 is fixed, but no matter – you wouldn’t want to replace it if you could. I observed excellent optical performance from this lens, with good sharpness throughout the entire frame and possibly just the tiniest bit of softness in the corners. I took about a half-dozen captures subjecting the lens to scenes that would tend to promote chromatic aberration with no negative results to report. Distortions such as barrel or pincushion are not apparent in images with straight lines deliberately composed toward the edges of the frame. In a perfect world SIGMA might have made this lens a little faster than f/2.8 to help take up some slack for that lack of stabilization, but given its optical excellence f/2.8 is not too onerous a price to pay. SIGMA notes that the lens does its best work at f/5.6 and f/8. Here’s a couple looks at images with texture throughout the frame that allow you to get an idea of the sharpness of this lens from edge to edge.

I do have one gripe that is lens related, however, and it is that SIGMA has seen fit to make the lens hood an optional accessory rather than including it as standard equipment. Come on guys, you’re getting $1000 for this camera, the least you could do is include a $40 lens hood.

Video Quality

Despite that excellent lens the DP2 video performance is nothing to write home about. With even entry-level compact digitals boasting 720 HD video these days, the DP2’s 640 x 480 VGA resolution and mono sound are decidedly off the pace. Despite its unique pixel construction the sensor on the DP2 is still a CMOS, and as such may be susceptible to rolling shutter effect. Actually, there’s no “maybe” about it – the DP2 generates a fair amount of rolling shutter in images that are panned at exaggeratedly fast paces. You wouldn’t ordinarily pan at such high speeds, but if you’re capturing a video of a fast-moving object don’t be surprised if vertical subjects in the background appear skewed as the camera pans past them. Another knock on the DP2 video is that there is no continuous autofocus – focus is established with the initial pressing of the shutter button to focus and initiate capture, and remains at the same point for the balance of the clip. In fact, even if you’re in manual focus whatever distance you chose as the initial focus point remains for the balance of the clip – you can’t manually change focus to account for varying distances with your subject during video capture.

Image Quality

What the DP2 does well, really well, are still images. Default images out of the camera were very pleasing as to color rendition and sharpness, but there are myriad adjustments available if the default settings don’t meet with your approval. This camera unquestionably produces the finest still images of any compact digital camera that I’ve reviewed. I’m not sure if I go so far as to agree with SIGMA’s assessment that the unique sensor of the DP2 produces images with a near 3-D quality, but images out of this camera are just gorgeous, be they RAW or JPEG. Here’s a look at two JPEGs; the first was a raw file converted to a TIFF file and later a JPEG – the second a JPEG fine straight out of the camera.

While SIGMA advertises the resolution of the DP2 sensor as 46mp, they quietly acknowledge that this rating is a product of the unique three-dimensional RGB design of their pixels and that the calculation for resolution of their sensor, known as a Foveon, differs from the traditional CMOS sensor, known as a Bayer. Sigma evaluates the DP2 sensor as comparable with a Bayer sensor with a resolution of 26 to 30 megapixels. Whatever the actual resolution of the DP2 is, the still image quality speaks for itself.

The DP2 offers a color palette including standard, vivid, neutral, portrait, landscape, B&W and sepia options – but B&W and sepia are not available when shooting RAW files. Here’s a look at that palette:

Standard                                                                           Vivid


Neutral                                                                             Portrait


Landscape                                                                         B&W


Sepia

Auto white balance was used for virtually all the images captured for this review and worked well across a range of light with the exception of incandescent, which shot a bit warm. The DP2 also offers daylight, shade, overcast, incandescent, fluorescent and flash preset values along with a custom setting.

Evaluative metering is the default exposure calculating mode, and divides the screen into 256 segments to analyze for determining the correct exposure. The system did a pretty good job under most lighting conditions, although it did have a bit of a tendency to clip some highlights in high contrast scenes. This performance is not unusual for compact digital cameras and when I looked closely at histograms for some of the scenes it appears the DP2 strikes a fine balance between highlight and shadow, setting exposure so that there’s just a little bit of highlight lost while at the same time minimizing the amount of shadow detail that is lost. The camera also offers center weighted and spot metering options.

High ISO noise performance with the DP2 was unimpressive.

ISO 100                                                                             ISO200


ISO 400                                                                             ISO 800


ISO 1600                                                                           ISO 3200

ISO 6400

100 and 200 ISO levels are virtually indistinguishable from one another, and 400 is quite close although with 100% enlargement pixel peeping you can see a tiny bit of grain starting to appear. 800 drops off a bit from 400 although it’s still fairly good, but close scrutiny shows that noise is definitely beginning to appear – if you have the option to satisfactorily make the shot without resorting to 800 ISO, by all means do so as the 100 to 400 ISO range is clearly the strength of this sensor. That having been said, here are two versions of the same five second exposure of the International Space Station as it passed over California. The capture was taken at 800 ISO and the first version is the JPEG fine image as it came directly from the camera – the second has been post processed in Photoshop CS5 with a bit of noise reduction, added contrast, saturation and sharpening over and above the original capture.

The DP2 sensor has clearly hit the wall at 1600 ISO – increased grain and colors are dramatically beginning to fade, and the 3200 and 6400 settings continue the dramatic downhill trend. Colors have faded so badly at 6400 that the image is almost a black and white. As mentioned earlier the DP2 does not have stabilization, so keeping shutter speeds up to help thwart camera shake can be helped by shooting the camera at 200 ISO whenever possible – this gives you quicker shutter speed than identical camera settings at 100 ISO with little, if any noise penalty.

It’s interesting to note that if you have the DP2 set to Auto ISO the camera will select from 200, 400 or 800 ISO in calculating exposures. You cannot select Auto ISO in the manual (M) shooting mode – the camera selects 200 ISO if you switch into manual from any of the other auto modes with Auto ISO selected. SIGMA recognizes the DP2 just doesn’t do very well with ISO settings above 800.

Additional Sample Images


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