Sigma 30mm F1.4 DC HSM "Art"
Aberrations and Color
On this page, we will be taking a look at how the Sigma 30mm is able to suppress ghosting, flare, and chromatic aberrations (fringing). We will also example contrast and color.
The Sigma 30mm does an exceptionally-good job of suppressing chromatic aberrations in the center of the frame, where it is only possible to provoke it in direct sunlight, and even then, it is mild.
It's a different story near the edges, where purple fringing is noticeable in daylight and very prominent in direct light.
In the corners the purple fringing thickens and may be a challenge to remove using software. We can conclude that the lens's distortion is related to the areas in which fringing may become prominent.
Click on any thumbnail below for a 100% crop of the original image.
As with virtually all wide-aperture lenses, in addition to purple fringing near highlights, red/green fringing may be present in out-of-focus areas. This is due to an optical phenomenon known as spherochromatism, in which objects in front of the focal plane take on red fringes, and objects behind the focal plane take on green fringes. Spherochromatism can be observed in the sample photos in the "Contrast" section at the bottom of this page.
Ghosting and Flare
The supplied lens hood is large and does a good job of preventing flare in typical shooting scenarios. We were able to provoke some flare and internal reflections, but even then the lens coatings typically did a good job of keeping it to a minimum. Refer to the sample photos below for a few worst-case scenarios, and click on any image to enlarge.
Contrast and Color
In general, the 30mm delivers good contrast and we found the Pentax K-3 to meter accurately with this particular lens. The only exception to this is F16, which led to consistent underexposure by about a third of a stop, as you may have seen in our outdoor sharpness test image earlier in the review. The image ended up being underexposed even though the shutter speed was increased by one stop compared to its value at F11.
Colors reproduced by the lens were vivid and true-to-life. The only issue we noted with respect to contrast is minor: at F1.4, the image typically ends up slightly warmer than at F2 and not as contrasty, necessitating a slight tonal adjustment and a contrast boost. This can partially be attributed to the vignetting that's present wide-open, which may adversely affect the camera's processing algorithms.
Again, the shift in white balance is very minor, but the contrast is undoubtedly superior when the lens is stopped down.
The lens coatings and hood on the 30mm help keep ghosting and flare to a minimum, and we are satisfied with the performance of the lens in this respect. Purple fringing is well-controlled in the center of the frame, but it is quite prominent near the edges and in the corners. Color reproduction and contrast is very good. We consider the fringing to be one of the optical weak points of this lens, together with the distortion we mentioned earlier.