Sigma DP1S 16.6 mm f/4

What do you get when you combine a Foveon sensor from a DSLR, a body from a point and shoot, and give it an excellent 16.6 mm f/4 lens(28mm equivalent field-of-view in 135 format)? The Sigma DP1S.

This review concentrates on the lens, I will add more about the body later. The DP1S is due to be replaced by the DP1X this summer, but retains the same great lens. The DP2S is much the same as the DP1X, but has the 24.2mm (41mm equivalent) lens.

The lens is a 6 element, 5 group design with a minimum focus distance of 11.9″ (30mm). It extends out when the camera is powered on, which is slightly inconvenient.

The optical performance of this lens is very good. It is sharp at the corners, but even sharper at the center. CA is well controlled for a lens of this field of view. The largest drawback to it is the minimum focus distance is not very close. The lens peaks at about f/5.6 but is good from f/4-f/8. Diffraction might be noticeable at f/11, but still perfectly reasonable.

What I would like to add next is a color sharpnessI use this to refer to the MTF50I use this to refer to the MTF50 graph. This is how contrasty the lens is, and correlates with perceived sharpness. A lens with high MTF50 will have a short transition period between a white and black edge. graph. This is how contrasty the lens is, and correlates with perceived sharpness. A lens with high MTF50I use this to refer to the MTF50 graph. This is how contrasty the lens is, and correlates with perceived sharpness. A lens with high MTF50 will have a short transition period between a white and black edge. will have a short transition period between a white and black edge. test. The current lens chart measure B&W sharpnessI use this to refer to the MTF50I use this to refer to the MTF50 graph. This is how contrasty the lens is, and correlates with perceived sharpness. A lens with high MTF50 will have a short transition period between a white and black edge. graph. This is how contrasty the lens is, and correlates with perceived sharpness. A lens with high MTF50I use this to refer to the MTF50 graph. This is how contrasty the lens is, and correlates with perceived sharpness. A lens with high MTF50 will have a short transition period between a white and black edge. will have a short transition period between a white and black edge., but the Foveon sensor excels at color sharpnessI use this to refer to the MTF50I use this to refer to the MTF50 graph. This is how contrasty the lens is, and correlates with perceived sharpness. A lens with high MTF50 will have a short transition period between a white and black edge. graph. This is how contrasty the lens is, and correlates with perceived sharpness. A lens with high MTF50I use this to refer to the MTF50 graph. This is how contrasty the lens is, and correlates with perceived sharpness. A lens with high MTF50 will have a short transition period between a white and black edge. will have a short transition period between a white and black edge. since it has 3 color sensels for each pixel in the output image. However, given that the Foveon only produces a 4.7 MP image, it still does good even on the B&W chart that is targeted towards Bayer sensors.

Sample Chart

MTF 50 (SharpnessI use this to refer to the MTF50I use this to refer to the MTF50 graph. This is how contrasty the lens is, and correlates with perceived sharpness. A lens with high MTF50 will have a short transition period between a white and black edge. graph. This is how contrasty the lens is, and correlates with perceived sharpness. A lens with high MTF50I use this to refer to the MTF50 graph. This is how contrasty the lens is, and correlates with perceived sharpness. A lens with high MTF50 will have a short transition period between a white and black edge. will have a short transition period between a white and black edge.)

MTF 20 (ResolutionI use the term resolution to refer to the MTF20I use the term resolution to refer to the MTF20 graph. This is how well the lens can resolve fine detail, but the contrast is low at this point. graph. This is how well the lens can resolve fine detail, but the contrast is low at this point.)

Lateral Chromatic AberrationDifferent wavelengths (colors) of light have different magnifications and produce colored halos around high contrast objects near the frame edges.

TV Distortion

Test chart data gathered from Imatest software.

Conclusions

This is a great lens with very good to excellent optical performance. The only thing it is lacking in is minimum focus distance and the fact it is tied to the camera. It would be nice if it were f/2.8, but f/4 isn’t bad. The aperture combined with the minimum focus distance means it can be tough to separate your subject from the background, but the bokeh is decently nice and rarely unpleasant when it does show.

Buying a DP1S could mean you don’t have to buy the same focal length lens on your DSLR, and some of those lenses can be a large percentage (if not more) than what the DP1S costs. If you want to shoot with the 16.6 mm, you only have to pull out the DP1S.