Sigma SD1 Optics
Sigma SD1 Optics
The Sigma SD1 is sold body-only, or bundled with one of three Sigma lenses: the 17-50mm f/2.8 EX DC OS zoom, 30mm f/1.4mm EX DG HSM prime, or 85mm EX DG HSM prime. The test results below are from the 17-50mm f/2.8.
Bundled Zoom Lens Test Results
Very good far-field performance from the 17-50mm f/2.8 lens when stopped-down.
The SD1 is available bundled with a Sigma 17-50mm f/2.8 EX DC OS lens, which has a slightly lower zoom ratio compared to typical kit lenses, but this lens starts wider than most (17mm or about 26mm equivalent) and is also much faster than most (f/2.8 constant maximum aperture). Sharpness and contrast are quite good at wide-angle (17mm) and f/8, though corners and edges are a touch soft, particularly on the right side. Some noticeable chromatic aberration is also visible in the corners and edges. At medium focal length (~33mm), sharpness is very good across the frame when stopped-down to f/8. Very minor chromatic aberration can be seen at this focal length, but performance was still quite good. Performance was also quite good at full telephoto and f/8, with very good sharpness and negligible chromatic aberration.
A larger-than-average macro area for a standard zoom lens, with very good detail. Flash exposure was a bit dim, and the lens casts a large shadow at closest focus.
|Macro with 17-50mm lens
|Macro with Flash
The Sigma SD1 captured a larger-than-average macro area with the 17-50mm zoom lens, measuring 4.62 x 3.08 inches (117 x 78 millimeters). Detail was very good but just a touch soft, and there was additional softening in the corners despite being stopped down to f/8. (Most lenses have some softening in the corners at macro distances, though.) The Sigma SD1's flash throttled down a bit too much at minimum distance and the lens cast a large shadow making the exposure with the built-in flash dim and very uneven.
Moderate distortion at both wide-angle and full telephoto with the 17-50mm lens.
|Barrel distortion is about 0.5 percent at 17mm|
|Pincushion distortion at is about 0.4 percent 50mm|
The Sigma SD1's 17-50mm lens produced about 0.5 percent barrel distortion at wide-angle; lower than average but still slightly noticeable in its images. At the telephoto end, there was about 0.4% of pincushion distortion, which is about average and also noticeable in some shots. This is the tendency for the lens to bend straight lines outward (like a barrel -- usually at wide-angle) or inward (like a pincushion -- usually at telephoto).
Chromatic Aberration and Corner Sharpness
Low to moderate chromatic aberration from the 17-50mm lens. Very soft corners when wide-open, slightly soft when stopped down.
Chromatic Aberration. Chromatic aberration was moderate in the corners at the full wide-angle setting of the Sigma SD1's 17-50mm lens, exacerbated somewhat by the softness. At telephoto, chromatic aberration was very low and hardly detectable. (This distortion is visible as a slight colored fringe around the objects at the edges of the field of view on the resolution target.)
Corner Sharpness. The 17-50mm lens that came bundled with our SD1 produced some very soft corners at both full wide-angle and full telephoto. The upper right corner was the softest at wide-angle though the other corners were also soft, and blurring extended part way into the frame from the right, but less so from the left. The center was a touch soft. At full telephoto, the lower left corner was the softest, but again the other corners were also soft. The center was also quite soft, suffering from low contrast. There's also some minor vignetting (corner shading) at both ends of the zoom as indicated by the darker corner crops, though the amount of darkening is pretty low given the speed of the lens (f/2.8).
Stopped-down to f/8:
|Wide, f/8: Upper right
Softness: Slight blurring
|Wide, f/8: Center
C.A.: Very low
|Tele, f/8: Lower left
C.A.: Very low
Softness: Moderate blurring
|Tele, f/8: Center
C.A.: Very low
Corner softness improved dramatically when the lens was stopped down to f/8, but corners were still a bit soft. The center however was quite sharp at both wide-angle and telephoto. Chromatic aberration was about the same (the strong blurring wide-open made it seem a little worse), and vignetting was negligible
A second lens tested better wide-open, but wasn't as sharp stopped-down, so be aware of sample variation.
Sigma SD1 Viewfinder
Viewfinder Test Results
Good accuracy from the optical viewfinder.
The Sigma SD1's optical viewfinder showed about 98% coverage in our test, matching Sigma's specification. This is good performance, though below average for an SLR in its price range. The SD1 does not support Live View mode, so its LCD monitor cannot be used to frame images.
The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Sigma SD1 Merrill Photo Gallery .
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