The delay in the 1Ds mkIII may be caused by Canon trying to find a way to make a 22mp sensor with per-pixel performance (noise and/or DR)equal to their existing 17mp sensor.
Dan,
It would be fascinating to find out what ideas and possibilities the guys in Canon's labs are currently working on. Is there an unusual delay between the 1Ds2 and 1Ds3? We have only one precedent here and that's the interval between the 1Ds and 1Ds2. How long was that? I don't see that Canon is under any obligation to bring out new models in a clockwork manner. Also, it doesn't seem good marketing policy to have too many goodies competing with each other for the consumers' dollar. It tends to dilute the return on R&D and setup costs.
The second issue is that higher-resolution sensors are often not equal to lower resolution ones in other aspects of image quality (such as noise and dynamic range).
This only applies when all else remains the same. Perhaps it's odd that no manufacturer seems to have pulled out all the stops to produce a high DR camera at the expense of resolution. Would there be a market for a 6mp full frame 35mm sensor with 16 bit processing and an extra couple of f/stops of DR?
The current level of dynamic range in DSLRs is roughly that of color negative film. Most photographers seem reasonably happy with it, but I agree that Canon does not want to go backwards in this area.
I can't see why there should be an insurmountable obstacle to producing say a 50mp 35mm sensor with noise and dynamic range characteristics at least as good as the current 1Ds2. For dynamic range and noise to remain the same on the same size print, it is not necessary for the smaller pixel to have the same low noise and the same DR as the larger pixel. All that is necessary is to keep noise and DR the same
per unit area of sensor, and this could be achieved by reducing read noise and increasing quantum efficiency.
Let's consider what might be involved with our imaginary 50mp camera which would have a pixel pitch of half that of the current 1Ds2. If the light gathering capacity of the 4 smaller pixels in total were equal to that of the one larger pixel and, if the read noise of each of those smaller pixels was no greater than 1/4 the read noise of the larger pixel, then DR and noise would be the same for any given size print, but the 50mp camera would produce higher resolution and more detail on a sufficiently large print.
It might also be possible, as manufacturing processes develop, to place all the photon receptors on one side of the chip and some, if not all, of the processors, such as analog preamplifiers, on the reverse side of the chip. That would allow the photodiodes to be larger within the same pixel pitch.