. . . The only real way to improve noise at a given ISO is to use a bigger
sensor. This means a bigger (and probably slower) lens. (Note that
the FZ lenses got slower when the sensor sizes went up.)
Or presumably
a) to revert to a sensible no. of pixels on the same size sensor and
achieve better IQ - first company to do that should get an Award for
Valour and Intelligence.
Decreasing pixel count while holding sensor size the same will actually decrease image quality. It is
entirely a myth that, all other things equal, a lower pixel-count sensor provides a better image.
Consider two sensors of the same area, one 12MP (4000x3000) and one 3MP (2000x1500). The 12MP image can always be downsized via pixel-binning down to 2000x1500, in which four pixels are averaged to get one output pixel.
This will produce an image identical to the 3MP sensor, since the four pixels that were averaged together have the same light-sensitive area as one 3MP pixel. But there's no way for the 3MP sensor to capture the extra detail that the 12MP sensor can in good light.
Yes -- you won't be able to resolve very fine low-contrast detail at high ISO on the 12MP sensor, because it will be swamped by noise. But the 3MP sensor can't resolve it
either , since it simply lacks the resolution.
However, the 12MP sensor
can resolve fine high-contrast detail at high ISO, since the contrast is high enough to stand out above the noise. The 3MP sensor, however, again lacks the resolution to do this.
It's certainly true that 100% crops from high pixel count sensors don't look as good. Shot at high ISO, the 12MP sensor's 100% crops will be full of noise. But they're certainly better than a 3MP image viewed at 200%.
It's also certainly true that the advantage in detail offered by more pixels diminishes at high ISO, and that you suffer diminishing returns as the pixels get tiny. The step from 2MP to 3MP is much more significant than the step from 8MP to 12MP, for instance.
But, all other things (quantum efficiency, microlens stuff, etc) being equal, the image from a high pixel-count sensor of the same size will be at least as good as the one from a low pixel-count sensor.
Now, there are certainly usability issues with high pixel counts: they take more RAM to buffer, longer to process, longer to write to the card, etc. At some point it becomes not worth it to increase pixel counts any more, and we're certainly close to that point. But you can't gain an IQ advantage by going backwards.
or b) to improve the sensor technology.
What do you suggest that they do? There's nothing you can do to a sensor to make the
light itself falling on it less noisy. Noise is not the fault of the sensor.
All you can do is collect
more light . To do that you either need longer exposures, larger sensors, or brighter lenses. Panasonic's already done wonders for the "longer exposures" angle by adding OIS to P&S lenses.
Now we can either get bigger sensors or brighter lenses, and as you point out bigger sensors aren't an option for the FZ line. That leaves brighter lenses as the only thing they can do to improve low-light IQ on the camera end.
On the processing end, they can certainly improve noise-reduction algorithms, since the Venus III one is pretty bad (and far too aggressive). Thankfully there's a RAW mode on the FZ's so we can bypass it and do it ourselves (or, more often, not do it).
