After held a 645D a few days before and checked for its street price, I have some thoughts to wonder what cost that much for a MF DSLR? And, are those "differentiators" of the 645D really worth for paying that significant extra premium? How long will take for those advantages to vanish, or at least to be less significant? (in nowadays when the technologies are growing so fast..)
To begin with the investigation, let's go back to the sensor size/pixel width talk I made last time for some MF DSLRs and others. Recently, after completed my in-depth full review on the Canon 550D and also brief tested the S0ny NEX-5 and purchased the NEX-3 myself, I found that in fact the Image Quality and Noise Control of those latest DSLRs and sensors (and their image processing as well) are actually not bad. In fact, I found that both models/sensors are not worse than the noise performnace of the K-x, if they are not better, even though the K-x has already been highly praised by Pentaxians for its "superior" noise performance at higher ISO speeds. (Well, Pentax people are amazed for what the K-x can give for the results just because there is a K-7 in comparison! Right? :-o)
The 645D has 40 Megapixels with a (square) pixel pitch width of 6.1 um. The 550D has a resolution of 5184 x 3456 pixels on a 22.3 x 14.9 mm sensor. As such, the pixel width of its sensor is of 4.3 um only, which is only 50% in area per pixel when it is compared to the 645D sensor. If that's what the current and latest technologies, no matter for the manufacturing process of the sensors as well as the associated image processing techniques (for both the hardware and software), could give acceptable or even good results, then we can calculate the maximum pixels and count that can be put into a 135 Full Frame DSLR, which is yet considered as the mainstream product for most (for advanced users/"richer" amateurs anyway).
Reverting the maths and calculating packing 4.3 um sized pixels on a 36 x 24 mm full frame sensor will give an overall resolution of 8372 x 5581, which gives an aggregate pixel count of 46.7 Megapixels, which is just more than the pixel count of the current 645D actually.
But of course, with the same sensor size of the 645D, we can have a DSLR with 10232 x 7674 = 78.5 Megapixels, which is just huge in number! But do we need that anyway??
So, my quick conclusion is that the Full Frame sensors will eventually reach and exceed the pixel count of that of the current 645D, even with the current proven/mature technologies that are already adopted and used in the latest APS-C sensors of Canon and Sony in their latest "low-end" (but actually high-end in real!) DSLR models. As there is still no popular 135 FF sensor that is more than 25 MPs at this moment, we shall still need to wait and see if any of the sensor vendors can make it later on - but possibly the day will come sooner than we would expect - as the technologies are already there. One more thing to note is that those 21 and 24M FF sensors of Canon and Sony were designed and put into mass production at least about two years ago. So, I do believe that if they are willing to make one, they could!
So, with the above conclusion and prediction in mind, the high resolution and high pixel count advantage of the 645D will soon vanish in a year or so as soon as when 135 FF DSLRs and sensors are catching up in this regard. As such, it should be wise to stay away from the MF even if you like it a lot, considering the huge investment probably cannot be safeguarded for just a bit longer. My believe is that the 135 FF will become the MF of the old film days, as IQ wise they will be more than adequate for 99% of use for people on this planet, no matter they use their cameras professionally or just amateurishly.
For other general shooting purposes and when smaller cameras and systems are desired, the APS-C will be the way to go. So, how about micro-4/3 then? I guess they will be killed by the APS-C ILDCs/EVILs eventually, as people don't need cameras that are not as small as and as "versatile" as compact P&Ses but without the minimum level of IQ that APS-C systems would give. (Honestly speaking, I am not using my GF-1 anymore with the purchase of my new NEX, as the IQ difference is just huge! Even if when I haven't got my NEX, I have already rarely to pick up my Girl Friend and I would just use my "huge" K-x and Pentax APS-C system instead.)