Virtually everyone who bought a Sigma Merrill camera did so for the image quality. We knew what we were giving up in performance - processing speed, low light imaging, etc.
We signed on to the flaws because the image quality was so good.
The Quattro cameras are compromises. Speed and low light performance are better in the quattro cameras but this was done by sacrificing image quality.
In my view, the enhanced performance of the quattro cameras is not sufficient to make up for the loss in image quality.
The quattro cameras still perform slowly compared to cameras other than the Sigma Merrills.
So I think Sigma lost their way with the quattro cameras. Sigma needs outstanding image quality to stand out from the others. Why take a step back in IQ? This is a huge mistake for Sigma.
It is too bad - the Merrill cameras were (and are) special.
