The day before yesterday, Sigma US announced further details about the launch of the DP0 Quattro. At the same time, the usual graphs and figures appeared on the Global Vision website; they illustrate the imaging performance of the lens. I have inserted them below so you can get an idea about the sharpness, vignetting and distortion of the 14mm f/4 prime.
While the miniscule distortion of less than one percent has already been announced, there has been virtually nothing about the remaining aspects of the picture quality.
Going by the MTF graph, the sharpness appears to be almost too high to be true for such a WA lens. If I am interpreting the graph correctly, the entire picture should be a bit sharper with the 14mm f/4 than with the excellent 30mm f/2.8 or 50mm f72.8 lenses of the DP2Q and the DP3Q, respectively. If this is confirmed in practice, the DP0Q would be one of the sharpest cameras with WA optics in existance.
The fly in the ointment is the pronounced vignetting which is on the high side even after stopping down to f/8 or f/11. While vignetting can be corrected rather easily with a correction-profile, using such software-based corrections one always exchanges one evil for a different one. The more one lightens the corners, the more pronounced is the noise. That is why, as a user of a camera with a Foveon-sensor, one should avoid using the vignetting correction by all means. However, the sample pictures are going to show if avoiding using it is actually possible. Hopefully we will not have to wait for them for too long.