Nic, can you expound on that comment?
Thanks.
I think that it is important to differentiate between sensor performance and image quality; with sensor performance being numerical measurements of sensor output and "image quality" coming from how a camera records and renders an image and how that image looks after processing (whether done in-camera through the jpeg engine or manually). Something like dynamic range is easy to measure and easy to demonstrate, but it is a measure of sensor performance not image quality. Higher dynamic range means that a camera can operate in a larger window which is obviously a good thing. A camera with high dynamic range means that I can attempt to shoot a scene like this with subjects in shade against a fully sunlit background...
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...and be able to get something usable from it.
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Using a camera with less dynamic range like the G1X I would have had no chance in the example above. However, for me it doesn't necessarily follow that a camera with better sensor performance produces better image quality. Less noise is good but we talk about grain and quality of noise. Higher dynamic range is good yet we like to see contrast. High dynamic range imaging has been possible for many years in the form of multiple image exposure blending (but limited by the need for static scenes and a tripod) but the beauty of it still remains in the eye of the beholder. In the 90-something percentile range where you don't even have 12, 13 or 14 stops of dynamic range, dynamic range expansion is purely a matter of personal taste.
There are many aspects that go towards forming an image on a sensor which we don't have a means to quantify and so have difficulty make definitive statements about. I think a good example of this are the Sigma Merrill cameras which I suspect wouldn't score very well for sensor performance if they were ever measured by DxO and yet the one reason to buy those cameras is their image quality.
Relating all this back to the G1X, and noting that the G1X MkII uses a largely unchanged sensor according to reports from owners of the new and the old, it's sensor does not have a large dynamic range. In fact, despite allegedly using a cut-down version of the 18mp Canon APS-C sensor, the G1X has less dynamic range than that sensor, and less dynamic range than even the 15mp sensor that preceded it in the 50D (circa 2008). What I do find with the G1X is that for whatever reason, it's images are the easiest to identify from my library comprising of (edited raw) images from 25 different 4/3 to APS-C sized sensor cameras.
So, I say yes to the premise that that the G1X has lower sensor performance than it's contemporaries, and yes to the fact that as a result it has a smaller operating window than them, but I stop short at saying that that means it has lower image quality than them. What it can do is produce a different type of image quality, a kind of which I often prefer.
The biggest limitation that I find in a camera like the G1X is not it's sensor performance but rather it's overall usability and flexibility compared to a CSC like a high-end Micro 4/3 camera. As a result, in the two and a half years that I have had it, the G1X has tended to be the camera that I have used the least but is often the one that at editing time I wished that I had used more.