Sigma DP1 Merrill Exposure

Saturation & Hue Accuracy
Conservative saturation levels at base ISO, with slightly below average hue accuracy. Hue error increases and saturation falls rapidly at ISOs above 400, though.

Saturation. The Sigma DP1 Merrill's mean saturation of 104.6% at base ISO isn't as pumped as most cameras, so default colors may seem a little muted to some. The camera pushes deep red and blues a bit, but most other colors are pretty close to accurate or slightly desaturated from ideal. Saturation falls off rather rapidly at ISOs above 800, though, to the point where colors have lost about 50% saturation at ISO 6,400. It's not unusual to see a drop in saturation at higher ISOs, but we're not used to seeing it as dramatic as this except from other Sigma models (the SD1 had a similar drop in saturation at high ISOs). Most consumer digital cameras produce color that's more highly saturated (more intense) than found in the original subjects. This is simply because most people like their color a bit brighter than life.

Skin tones. The Sigma DP1 Merrill's Caucasian skin tones look fairly realistic in outdoor lighting using auto white balance, with a healthy-looking pink tint, though darker skin tones can be a little too red. Manual white balance produced flatter and more yellow skin tones. Where oversaturation is most problematic is on Caucasian skin tones, as it's very easy for these "memory colors" to be seen as too bright, too pink, too yellow, etc.

Hue. The Sigma DP1 Merrill showed a lot of small to moderate color shifts relative to the mathematically precise translation of colors in its subjects, resulting in a Delta-C color error after correction for saturation of 5.77 at base ISO. That's a little higher (worse) than average these days, and like saturation, hue accuracy dropped significantly at higher ISOs. Hue is "what color" the color is.

Saturation Adjustment
The Sigma DP1 Merrill lets you adjust the image saturation and contrast in 11 steps, from -5 to +5. As can be seen below, the saturation adjustment provides fine-grained adjustment over a useful range of control, however some colors are affected more than others. The saturation adjustment has almost no impact on contrast, though. That's how a saturation control should work, but we've often found interactions between saturation adjustments and image contrast (and vice versa) on the cameras we test.

The series of shots above shows results with several different saturation adjustment settings including the two extremes. See the Thumbnails index page for more (look for the files named DP1MOUTBSATxx.JPG). Click on any thumbnail above to see the full-sized image.

Exposure and White Balance

Indoors, incandescent lighting
Warm and reddish results with Auto white balance while the Manual setting is too cool and green. Best results with Incandescent setting, though still too warm. Slightly above average exposure compensation required.

Indoors, under normal incandescent lighting, color balance is very warm and reddish with the Auto white balance setting. The Incandescent setting is better, but still a bit too warm for our tastes. The Manual white balance setting on the other hand produced overly cool results, with a strong green tint. Overall, we preferred the Incandescent setting. The Sigma DP1 Merrill required +0.7 EV exposure compensation for this shot, which is a little higher than the +0.7 EV average needed among cameras we've tested. Our test lighting for this shot is a mixture of 60 and 100 watt household incandescent bulbs, a pretty yellow light source, but a very common one in typical home settings here in the U.S.

Outdoors, daylight
Slightly muted colors, though with somewhat high default contrast.

The Sigma DP1 Merrill struggled a bit under harsh sunlight, yielding muted colors and high contrast. We needed to use +1.0 EV exposure compensation for a bright face in our "Sunlit" Portrait shot. That's more than the average of +0.7 EV normally required for this shot, and it lead to a lot of clipped highlights in the mannequins's shirt and flowers. We found skin tones too yellow and flat in our Portrait shot with Manual white balance, preferring the more pinkish skin tones Auto white balance provided here. Colors are a bit cool and muted in our Far-field outdoor shot with Auto white balance. Default exposure was good, though, with almost no clipped highlights in the white building, though shadows are quite dark. Shadow detail is pretty good, though, with only the deepest shadows plugged by noise.

See full set of test images with explanations
See thumbnails of all test and gallery images

Resolution
Very high resolution, ~2,200 lines of strong detail from JPEGs, about 2,300 lines from converted RAW files.

Our laboratory resolution chart revealed sharp, distinct line patterns down to about 2,200 lines per picture height in both the horizontal and vertical directions in JPEGs, though it's a little difficult to call given the strong moiré pattern caused by the camera's somewhat high default sharpening in this shot. Complete extinction of the pattern didn't occur before the limits of our chart (4,000 lines) in both directions, and as expected, no color moiré is present. There are some pixel defects that were not well corrected, but that's not unusual.

We weren't really able to extract any more resolution using Sigma's Photo Pro RAW converter at default settings mainly because of its overly aggressive sharpening. When we turned sharpening down to a minimum in Photo Pro and then sharpened lightly in Photoshop, we could see resolution is closer to 2,300 lines in both directions, though chromatic aberration starts to interfere with resolution here. Use these numbers to compare with other cameras of similar resolution, or use them to see just what higher resolution can mean in terms of potential detail.

See our SD1 test results to see how Sigma's Foveon sensor compares to Bayer sensors in terms of color resolution.

See full set of test images with explanations
See thumbnails of all test and gallery images

Sharpness & Detail
Excellent sharpness straight from the camera, with very minor edge-enhancement in natural subjects. Moderate noise suppression artifacts at base ISO.

Sharpness. The Sigma DP1 Merrill produces images with excellent sharpness and amazing detail at base ISO, doing much better than a typical 16-megapixel Bayer sensor would do. Very few edge enhancement artifacts are visible on high-contrast subjects in the crop above left, which is also excellent. Edge enhancement creates the illusion of sharpness by enhancing color and tonal differences right at the edge of a rapid transition in color or tone.

Detail. The crop above right shows some detail loss due to noise suppression, as darker areas and areas of low contrast in the mannequin's hair show smudging and loss of definition. Still, a pretty good performance at base ISO. Noise-suppression systems in digital cameras tend to flatten-out detail in areas of subtle contrast. The effects can often be seen in shots of human hair, where the individual strands are lost and an almost "watercolor" look appears.

RAW vs In-Camera JPEGs
As noted above, the Sigma DP1 Merrill does a an excellent job capturing loads of detail in its JPEGs. As is usually the case, more detail can be obtained from carefully processing RAW files, though. Let's see how the DP1's RAW files compare:

In the table above, mousing over a link at the bottom will load the corresponding crop in the area above, and clicking the link will load the full resolution image. Examples are all shot at ISO 100, and include in-camera Fine JPEG, the matching RAW file processed through Sigma's Photo Pro 5.4 software using default settings, and another conversion with Photo Pro with its sharpening set to the lowest setting, then lightly sharpened in Photoshop with an Unsharp Mask of 100% and radius 0.3.

As you can see, Sigma's Photo Pro software produced an image very similar to the camera JPEG, though with slightly different exposure (about a 1/4 EV darker). Since Photo Pro seemed to oversharpen our resolution chart at default settings, we thought we may be able to do better by reducing sharpening to a minimum and then sharpening in Photoshop, but results are quite similar to Photo Pro's default sharping for this image. The Photo Pro conversion does show slightly better detail than the in-camera JPEG, but the DP1 did a pretty good job with this subject. (Note: We normally include an Adobe Camera Raw conversion here, but ACR and Lightroom do not support the DP1 Merrill's X3F RAW files at the time of writing (early-February, 2013), and we doubt they ever will.)

Here's a better example of how Photo Pro can out-perform the in-camera JPEG engine, even at base ISO. (Mouse over the links to compare.) 

Notice how the red-leaf fabric has much better detail and thread patterns are visible in the RAW conversion. This is better performance than some ~25-megapixel DSLRs. The lack of an image-softening anti alias filter coupled with a sensor that requires no color interpolation allows the DP1 to resolve fine chromatic detail at low ISOs well beyond what most Bayer sensors with similar or even significantly higher resolutions can do.

ISO & Noise Performance
Very good handling of noise vs detail up to ISO 400, but image quality quickly deteriorates at higher ISOs.

In-camera JPEG images contain very good detail and fairly low noise levels at ISO 100 and 200, with just a touch of luminance and chrominance noise visible in the shadows. As mentioned, though, fine detail particularly in the red channel already suffers at base ISO. There's some blotchy luminance noise at ISO 400, with subtle but cloudy chrominance noise as well, though detail is still pretty good. Image quality starts to go south quickly at ISO 800, though. Blotchy luminance noise gives our mannequin what looks like a case of the Measles, and cloudy chroma noise as well as some pattern noise (banding) is quite evident in the shadows and some midtones. These artifacts only get worse at ISO 1,600 and above with stronger luma and chroma noise, horizontal banding, and a drastic drop in saturation. Overall, well below average high ISO noise performance in JPEGs for an APS-C sized sensor. Note that the Sigma DP1 Merrill offers no control over noise reduction strength, at least not with the latest firmware available at time of writing (version 1.00.1.5665). Converted RAW files are better, but ISO 1,600 and above are still quite noisy and image quality at high ISOs is well below what most APS-C Bayer-filtered sensors deliver.

Of course, the impact of noise and detail loss are highly dependent on the size the photos are printed at, and pixel-peeping on-screen has surprisingly little relationship to how the images look when printed: See the Print Quality section below for recommended maximum print sizes at each ISO.

Extremes: Sunlit and low light tests
Very high resolution but with poor highlight preservation. Fair low-light performance, capable of capturing bright images in near darkness at low ISOs, though autofocus struggled and higher ISOs were very noisy.

Sunlight:
The Sigma DP1 Merrill struggled with the deliberately harsh lighting in the above test. The camera required +1.0 EV compensation to render a bright face in our "Sunlit" Portrait shot (the average for this shot is about +0.7 EV), and the DP1 Merrill clipped quite a few highlights in the mannequin's shirt and flowers, though shadow detail is good. Overall, though, below average performance here.

Because digital cameras are more like slide film than negative film (in that they tend to have a more limited tonal range), we test them in the harshest situations to see how they handle scenes with bright highlights and dark shadows, as well as what kind of sensitivity they have in low light. The shot above is designed to mimic the very harsh, contrasty effect of direct noonday sunlight, a very tough challenge for most digital cameras. (You can read details of this test here. In actual shooting conditions, be sure to use fill flash in situations like the one shown here; it's better to shoot in open shade whenever possible.)

Contrast Adjustment
Just like saturation, the Sigma DP1 Merrill's contrast setting offers 11 settings, between -5 and +5.

At its lowest contrast setting, the DP1 Merrill did a pretty good job of preserving highlight detail while bringing more detail out of the shadows.

The series of shots above shows results with several contrast adjustment settings, including both extremes. While you can see the extremes, it's hard to really evaluate contrast on small thumbnails like these, click on any thumbnail to go to the full-size image.

One nice feature of Sigma's contrast adjustment is that it has little effect on color saturation. Contrast and saturation are actually fairly closely coupled, it's a good trick to be able to vary one with out the other changing as well. Sigma did a good job here.

Low Light. The Sigma DP1 Merrill was able to capture usable images down to the 1/16 foot-candle light level (about 1/16 as bright as average city street lighting at night) at all ISO settings in our low-light tests, though noise was an issue at higher ISOs and lower light levels.

Color balance with Auto white balance is fairly neutral, just slightly cool, but images take on a strong magenta tint at higher ISOs. Noise is low up to ISO 400, though a hint of horizontal banding can already be seen in the red channel at this ISO. ISO 800 and above are quite grainy and blotchy with obvious chroma noise, color shifts, desaturation and banding. As mentioned previously, higher ISOs also have a strong magenta tint to them.

The camera's contrast-detection autofocus system was only able to focus on the subject down to just below the 1/2 foot-candle level. That's quite poor especially for a camera with a fairly large sensor and fast lens. To make matters worse, the Sigma DP1 does not offer an AF assist lamp either.

(Keep in mind that the longer shutter speeds here demand the use of a tripod to prevent any blurring from camera movement. A useful trick is to just prop the camera on a convenient surface, and use its self-timer to release the shutter. This avoids any jiggling from your finger pressing the shutter button, and can work quite well when you don't have a tripod handy.)

How bright is this? The one foot-candle light level that this test begins at roughly corresponds to the brightness of typical city street-lighting at night. Cameras performing well at that level should be able to snap good-looking photos of street-lit scenes.

NOTE: This low light test is conducted with a stationary subject, and the camera mounted on a sturdy tripod. Most digital cameras will fail miserably when faced with a moving subject in dim lighting. (For example, a child's ballet recital or a holiday pageant in a gymnasium.) Digital SLRs like the Sigma DP1 Merrill do much better than point & shoots, but you still shouldn't expect a quick autofocus lock with moving subjects.

Print Quality
Crisp and vibrant prints to 24 x 36 for ISO 100/200; ISO 800 capable of a decent 11 x 14; ISO 3,200/6,400 prints are unusable.

ISO 100 images are crystal clear and vibrant at 24 x 36 inches, with excellent color and detail; suitable for wall display up to 36 x 48 inches.

ISO 200 shots are also very nice at 24 x 36, with only slight loss of contrast in the red fabric swatch; wall display prints suitable up to 30 x 40.

ISO 400 prints are quite good at 20 x 30, but lose almost all contrast in our red swatch. Greens have odd spots of desaturation that are apparent regardless of print size.

ISO 800 13 x 19 inch prints show a bit of a brown, scorched look in yellow and orange colors. And the odd, desaturated splotches in greens that we noticed at ISO 400 are much more pronounced. 13 x 19 inch prints are very crisp, but noise is rather apparent. We'll call 11 x 14s good, but the green glitches are problematic.

ISO 1,600 yields 8 x 10's that look grainy and faded. The 5 x 7s are usable but still grainy, and the 4 x 6 inch prints quite crisp and reasonably clean, but still too muted in color to be called good.

ISO 3,200/6,400 prints are too grainy and muted to be usable, even at 4 x 6.

Like its big brother the SD1, the DP1 Merrill with its APS-C Foveon sensor is certainly capable of producing excellent printed images at low ISOs. We called the wall display good to 36 x 48, but even 40 x 60 looks good if you're just a few feet away. But the nature of the sensor which allows for such incredible low ISO images doesn't lend itself at all well to high ISOs, and it definitely shows in the prints. Once you get to ISO 800, the quality falls very quickly. Stay at ISO 400 and below and you will be quite happy printing your DP1 Merrill images.

Testing hundreds of digital cameras, we've found that you can only tell just so much about a camera's image quality by viewing its images on-screen. Ultimately, there's no substitute for printing a lot of images and examining them closely. For this reason, we now routinely print sample images from the cameras we test on our Canon Pro9000 Mark II studio printer, and on the Pixma MP610 here in the office. (See the Canon Pixma Pro9000 Mark II review for details on that model.)