I was very keen to review the sd Quattro for Digital Camera Magazine because it looked like a very interesting new direction for Sigma’s cameras and Foveon sensor technology. The Foveon sensor, uniquely, uses three sensitised layers to record colour information, not one. This means it can generate full-colour information directly for each photosite (pixel) in the image rather than having to interpolate it by ‘demosaicing’ the red/green/blue pixel array of a regular single-layer sensor.
So enough of the science. The point is that Sigma’s Foveon camera don’t necessarily deliver the megapixels of rival cameras but they do produce pixel-level detail that’s startling in its clarity. And that’s exactly what you get with the sd Quattro.
The autofocus is slow and can sometimes fail completely in low light (but I can live with that) but worse, the electronic viewfinder image is soft and slow to update (as if it’s being upsampled for the high-res display from a lower-res sensor feed), the image processing is slow and the Sigma Photo Pro software you need to process the raw files is slower still.
That’s not all. The colour rendition is good but the dynamic range is only average, and highlights clip easily, even when shooting raw files. The Sigma Photo Pro software seems powerless to pull them back, but maybe Adobe Camera Raw will do better when (if) Adobe adds sd Quattro raw file compatibility in the future.
The thing is, I really like this camera. It feels solid and well made, the rear screen is good and I like the way Sigma has positioned the information display to one side, not under the screen or overlaid on the image.
And I think Sigma has pulled off a really smart move by extending the lens flange well forward of the camera body so that it can use all of Sigma’s regular Contemporary, Art and Sports lenses (fitted with the Sigma mount). It’s a mirrorless body, but Sigma’s resisted the temptation to create an addition and confusing range of lenses just to exploit the shorter back-focus distance.
This is a great camera. One can only imagine what it would be like with a regular sensor, a good AF system and fast processing. The one thing that lets it down is the one thing Sigma, I suspect, is most proud of – the Foveon sensor.
So, sorry Sigma, but the Foveon doesn’t seem any closer to matching the all-round performance of a regular bayer sensor than it ever did. It’s super-sharp, but that’s not enough.
But if you ever make the sd Quattro with a (horror!) regular sensor, I think you could start selling quite a few cameras.