This really is a wonderful little camera and in terms of the quality of the images at it's base ISO of 100, surely the best fixed lens compact ever released for IQ. This is partly as a result of the amazing double sized 40MP jpgs. it processes in camera. I actually prefer them to the raw files, which is a good job since the Sigma Photo Pro software is mind numbingly slow and Brian at Iridient Developer isn't going to offer support because of the added complication of the Quattro files.
These jpgs. stand comparison with the 36MP files that come out of my Sony A7r and there would be little difference in large scale print resolution. The files overall are slightly different to the results from the DP Merrills, looking slightly more Bayer sensor-ish, but that is no bad thing for me, since there are less 'idiosyncrasies' to take care of.
I've also bought an old TEWE rangefinder zoom optical viewfinder, see below.
Now this is the ultimate 'tunnel vision' viewfinder, but it works and it's variably adjustable for the focal lengths, rather than click stops, so I can get an exact framing for the lens. I bought it to service those cameras I buy from time without viewfinders and it works on my Fuji X-A1 as well as my Sigma. Looks great as well.
The Sigma is an off the wall camera, with equally off the wall looks and I have to say, yesterdays excursion with the viewfinder was the most fun I've had with a camera for a while. Very 'old-school', very simple, very liberating. Brilliant images as well that look superb on my screen. How long I'll keep it who knows, but while it's here it will be a pleasure to use. If only Sigma could be persuaded to make an interchangeable system out of this with a proper integrated viewfinder. But I doubt that will happen, which is unfortunate. In the meantime the above outfit has a charm all it's own and if you are looking for something simple with breathtaking image quality then you could do worse than one of these. Certainly, as far as I'm concerned this beats the pants off all the other fixed lens compacts for image quality just as long as I don't stray above ISO 200, though it is usable up to ISO 800.
A unique camera and while it won't sell in large quantities the photographic world would be worse off without oddballs like this. File under 'flawed but addictive!'