Image Quality and Resolution
For the resolution chart images that appear in our camera tests, we use a series of the last-generation Sigma 105mm lenses in various mounts.
This lens was chosen not because of its availability in most mounts but because it was one of the sharpest on the market and would therefore allow us to gain the maximum resolution from the sensor. With the new 105mm model the increase in quality is not drastic, but there are areas that show improvements.
Image: The Sigma 105mm f/2.8 lens is also useful for capturing details, such as this graphic street shot. Nikon D700, 1/1600sec at f/2.8, ISO 200
Resolution at its sweet spot, between f/8 and f/11, shows little gain compared to the original lens, but while the old lens started to show a drop in resolving power when stopped down to f/16, the new model only starts to reduce quality beyond f/22.
This is an extremely strong performance and one that will allow the maximum quality to be realised from the highest resolution sensors. Vignetting can be seen when the lens is used at the maximum aperture on a full-frame camera. However, the appearance is slight and can easily be removed in raw editing, and it disappears when the lens is stopped down to f/5.6. When used on an APS-C body there is no sign of vignetting.
Neither barrel nor pincushion distortion is visible in our test images, and at this focal length you would not expect to find them. The lens produces a crisp contrast, which emphasises the sharp areas of the image against the out-of-focus areas. The increase from 8 to 9 diaphragm blades was designed to help produce a smoother out-of-focus area, or bokeh, but at the smallest aperture the blades don’t quite create a perfect circle and the jagged edges can be seen in the out-of-focus highlights it creates.
Resolution
We tested the Sigma 105mm f/2.8 EX DG OS HSM Macro on the Nikon D700 camera against the older Sigma 105mm f/2.8 EX DG lens. As the D700 is a 12.1-million-pixel camera, the values should be used for comparison and not as a value for the total performance of the lens.
