Review Date: September 8, 2014
Category: Serious Enthusiast
Photoxels Gold Award – Excellent Image Quality from RAW
IMAGE QUALITY
The Sigma dp2 Quattro is targeted to serious enthusiast photographers. It has 39 megapixel-equivalent (29MP effective) resolution on Sigma’s unique and proprietary APS-C (23.5 x 15.7 mm) Foveon X3 Quattro image sensor. There is no low-pass filter.
The Quattro sensor is a new Foveon sensor and differs from the Merrill sensor used in the older dp series cameras. It’s still comprised of three layers of photodiodes, each at a different depth within the silicon and each corresponding to a different RGB (Red-Green-Blue) color. The difference is that the topmost Blue/luminance layer is 19.6MP while the lower Red and Green layers are now at a lower resolution, at 4.9MP each. The lower resolution in the lower layers apparently accounts for the higher speed data processing and better signal-to-noise ratio at high ISOs. Add up the resolution of the three layers and you end up with a total of 29.4MP, which Sigma rounds off to 29M effective pixels.
Because of the unique way the Foveon sensor is built and gathers its light data, its actual resolution is a bit difficult to determine: is it 39MP (Bayer equivalent), 29MP effective, 19.6MP — or somewhere in between? It’s up for interpretation but I believe most photographers have moved past that discussion now. What they really care about is image quality. JPEG at Super High saves at 7680×5120 pixels, RAW saves at 5424×3616 pixels. A JPEG image is compressed down to anywhere between 12MB and 29MB. A RAW image occupies anywhere from 55MB to 64MB!!!
The Sigma dp2 Quattro has excellent JPEG image quality including very good low noise at ISO 100 with excellent detail preserved. Noise starts to show at ISO 200 but it is still very usable up to ISO 400. JPEG images at higher ISOs suffer from noise and loss of detail.
But you won’t be buying the dp2 Quattro if you intend to shoot JPEG. The dp2 Quattro (indeed all the dp cameras with Foveon sensor) shines the most when shooting in RAW, where image quality is simply excellent with low noise and exceptional level of detail preserved at the low ISOs.
It’s not for the faint of heart and you will have to do post-processing to bring out the best from this camera. Fans of the Foveon sensor usually use superlatives to describe the color and B&W images they get: “exceptional,” “outstanding,” “phenomenal” and “breathtaking” are some of the words used to describe the results they get from post-processing the RAW files.
| 30mm [45mm equiv.] F2.8-16 lens |
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| 30mm (45mm, 35mm equivalent) |
The dp2 Quattro has a prime lens. It’s fixed, i.e. not interchangeable. And it’s fixed focal length: 30mm [45mm equiv.] at F2.8-16. Sigma wins countless awards for its lenses and this prime lens seems perfectly suited to bring out the best in the new Foveon X3 Quattro sensor. The lens has 9 blades, focuses as close as 28cm and the lens barrel is threaded to accept 58mm diameter filters.
The picture above shows the coverage for 30mm [45mm equiv.].
There are three models in the “dp Quattro” series with the focal length of the lens being the main difference: the dp1 Quattro with a Wide 19mm [28mm equiv.]/F2.8 lens, the dp2 Quattro with a Standard 30mm [45mm equiv.]/F2.8 lens and the dp3 Quatrro with a Mid-tele 50mm [75mm equiv.]/F2.8 lens.
The Sigma dp2 Quattro has full exposure flexibility with PASM modes, and Program Shift.
The camera also provides exposure compensation (with Auto Bracketing) and Custom (Manual) White Balance. A Histogram can be displayed in both Live and Playback modes.
Shutter speed ranges from 30 sec. to 1/2000 sec. (though the entire range may not be always available, dependent on the chosen aperture).
The 30mm prime lens allows you to focus as close as 28cm (11 in.). This is not much macro capability and if you are into macro photography, you would need to check third party sources for the availability of a macro filter.
| Auto White Balance Indoors | |
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| AWB | Custom WB |
As the above two pictures show, though the Auto White Balance (AWB) is not quite accurate indoors under artificial lighting [I have two energy-saving fluorescent light bulbs on the ceiling], it however does a pretty good job. The Sigma dp2 Quattro allows WB to be easily set manually and this brings out the real colors. AWB works very well in natural light.
| JPEG ISO Comparisons | |
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| ISO 100 | |
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| ISO 200 | ISO 400 |
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| ISO 800 | ISO 1600 |
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| ISO 3200 | ISO 6400 |
The Sigma dp2 Quattro has 7 ISO settings going from ISO 100 to ISO 6400. The 100% crops above (area delimited by the white square) demonstrate the noise at the available ISO Speeds. At ISO 100, noise is under control. Noise starts to be visible at ISO 200 but is still usable up to ISO 400. Noise (with detail loss) is quite visible at higher ISOs. Overall, JPEG noise handling is not that great unless you stay at the low ISO 100.
As mentioned, the dp2 Quattro needs to be shot in RAW (or RAW+JPEG) to get the most out of the Foveon sensor. Image quality is then excellent, with excellent detail preserved at the low ISOs. Below are images that I shot in RAW+JPEG (Fine) and I applied AUTO adjustment in SIGMA Photo Pro 6.0.5 RAW Editor to the RAW images starting at ISO 1600. The images from ISO100-800 used the default Photo Pro settings for conversion to JPEG. Here are the JPEG (unretouched) and JPEG (from RAW, Default setting or Auto adjusted) side by side. At ISO 1600 and above, the black rectangle behind the tallest candle is smeared out.
| ISO Comparisons: JPEG vs RAW | |
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| ISO 100 – JPEG | ISO 100 – from RAW |
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| ISO 200 – JPEG | ISO 200 – from RAW |
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| ISO 400 – JPEG | ISO 400 – from RAW |
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| ISO 800 – JPEG | ISO 800 – from RAW |
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| ISO 1600 – JPEG | ISO 1600 – from RAW |
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| ISO 3200 – JPEG | ISO 3200 – from RAW |
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| ISO 6400 – JPEG | ISO 6400 – from RAW |
You would probably get better noise control if you first extract into TIFF and then process in Photoshop.
CA is apparent in very high contrast JPEG shots. The area delimited by the red square at top center, and reproduced at 100% crop at bottom right, shows purple fringing.
Our Long Shutter Speed test is a torture test for digital cameras. Here we test whether (and how well) a camera can lock focus, provide accurate WB and obtain a correct exposure in extreme low light situations. The Sigma dp2 Quattro passes this test very well.
The Sigma dp2 Quattro allows the use of a long shutter speed of up to 30 sec. in PASM modes, therefore allowing very nice night photography. Generally, with image sensors, noise becomes more prominent the longer the shutter is left open. Noise Reduction kicks in at long exposures and you’ll notice a longer processing time (approx. twice as long) before the next picture can be taken.
To test this noise reduction algorithm, we take a low-light indoors shot. I experiment a bit to obtain the optimum exposure, eventually settling on 30 sec. at F9 (-1EV underexposed). Even at this long shutter speed, the Sigma dp2 Quattro’s noise reduction seems to be working great, producing a nice smooth blurring effect of the background.
Overall, the Sigma dp2 Quattro exhibits excellent image quality with superb detail preserved when shooting RAW at the low ISOs.
Next: Sigma dp2 Quattro Photo Gallery
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