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Hi Jacques,
Just for future reference as an aid to translating my ramblings, I use "pixel density" as a shorthand for exactly what you said above. Pixel density is inversely proportional to pixel size, of course, and all the benefits you ascribe to bigger pixels are assumed.
The problem with those dreaming of a DX sensor that performs as well as today's FX sensor is that, due to the physics of sensor design, should such a DX sensor become available, there will surely be an FX sensor with equivalent pixel count that is a stop or two faster, just as exists with the D3/D300 (developed more or less at the same time), and that sets a new bar for low light performance. At that point, the D3 performance will be "has been" technology that will interest no one here  . It's a horse race and the horse wearing the low density (same pixel count) FX sensor will always win the race by the end of that product cycle. Of course, at that point, at least the old FX technology should wind it's way to Prosumer D80 level cameras and we will all be faced with this decision, regardless of budget .
I got to thinking about this the other night. I shoot wildlife, but that is just one thing I shoot. It is the most demanding of technology and investment though, because of the glass and the never-ending search for reach and speed. I started looking for comparative images between my D2H (4mpx) and D200 (10mpx) images, especially looking for images where extensive cropping was needed. I found a landscape scene that I shoot often, more or less as a real world test chart (the bayside scene if you've followed my prior links). And yes, I found a picket fence that was well defined by the D200 (although a bit soft at 100% compared to the smaller D2H image). The D2H image was too small to properly define the fence, which took on strange geometric patterns typical of Bayer sensors trying to do things beyond the limits of resolution. BUT, on the whole, it's hard to find that extra resolution, despite the fact that I am still convinced the lens I used (a 35/1.4 Ai) is almost surely resolving beyond even the D200 sensor in a technical sense. The point being that although I could say AHA!, here is the benefit of the 10mpx sensor, I don't think I would buy a body just to get that res.
(or, on second thought, if I was in the business of printing 20x30 prints that would blow away the viewer with it's details, that picket fence might make the image...)
What was interesting, though, was that tree leaves and shrubbery, at a distance of several hundred feet, were generally no better defined. Just bigger and a bit fuzzier on screen at 100%. Bayer sensors deal with irregular natural shapes much better than picket fences, which are essentially test charts with parallel lines that show you lpp stats. There are only so many picket fences to be shot, of course.
What the D200 does do, though, for sure, is make me feel better about highly cropped wildlife images (or maybe macro). With D2H images, I hit Ctl+ twice and I'm at 100% and my mind screams Oh No! I need more! With my D200 images, I get that satisfying extra Crl+ or two before I hit "the wall" at 100%. That's all psychological, to a great extent. It may not be, though, in the case where I have a very tight crop and all I can hope from it is a 800 pixel sized image for my web galleries. You know those shots- they will never be good 8x10's, but maybe they will make an interesting web image if the subject matter is uncommon. In principle I can take that relatively cleaner D2H image and just up-res it, but for web imaging I just never like the end result of up-sizing. It looks "fake" to me, even if the image is clean as a whistle. Maybe it's just me and my biases.
I'm going to keep doing that search because it's helping me to frame my thoughts on this matter. It does make me think that, although I have not searched for this in particular, I do not recall seeing many if any good examples of where, for example, a D300 image of the identical scene taken with a D3 actually added huge value to a real world image. And, of course, it is very difficult to execute in real life; you really have to set out to do a specific test.
I did come to some better understanding of the decision making process, though, for myself and maybe others that are trying to make the DX/FX decision... a clarification of what I said above...
There are certain benefits to FX, and those benefits are, to at least a great extent, inarguable. No one argues that a D300's high ISO sensitivity is just as good as D3. They can nit-pick the extent of the difference, number of stops, etc., but no one questions the basic concept. Nor does anyone question that FX delivers wider views with wide angle FX primes. That is truly inarguable. You can only nit-pick IQ issues.
On the other hand, the primary benefit to the DX sensor (assuming same pixel count of course) is that "reach" issue, which is hotly debated. It is not a given. At best it takes a huge amount of skill to bring home that resolution. If you are a wildlife shooter you are using a TC with either format much or most of the time and that does not work in the favor of DX because there are no magic TC's that make lenses sharper.
So, you have very tangible and inarguable benefits to FX, and a very arguable and very tenuous benefit to DX. If price was not an issue, which would you take, the two slam dunk benefits or the tenuous one?
Hmmm... food for thought...
Neil
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Neil
Nikonians Team
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