Top-end digital concerns

[Clement Apffel]

After a lot of time spent reading technical reviews and articles, I still do not understand some of the major concern of current digital hardware.

My main interrogations are about the physical size of pixels:

In the first hand we have very respectable theoretical calculation about the diffraction related with the diameter of the pixel size. Those calculations bring us to many known facts like those:

Under the size of 9 nanometers, the image quality falls quite hardly. The ratio signal / noise forces to use heavy corrections in the DSP.

With a given pixel size, you won’t be allowed to close your aperture more than a given value under which the size of the Airy disc becomes greater than 2 pixels diameter and makes the capture quality fall drastically.
This value is known as being 2.12*pixel size (in nanometers)
Example: the Canon EOS 5D has 8 nm pixels. 2.12*8=16.96. that means that you can’t close your diaph under f/17. and that is not related to focal length nor CCD size. It is just a plain relation between pixel size and Airy disc diameter.

And on the other hand we have gear producers that continue the Mpixels race.
In February 2k8 Sony announced its 24.6 Mpixel 24x36 mm CMOS and few month later Nikon uses that CMOS in its D3x.
That is 6.4nm pixels.

Digital backs show pixel size between 5 and 7 nm too. And one wouldn’t be a fool to bet on the fact that future releases will show more pixels on same sized sensors.

So what is all that about? I’m getting confused.
And one can find almost none field feedback about those aperture / pixel size problem. It doesn’t appear to be a well known technical issue.

Is it just theoretical hair splitting ?
Is it just commercial big numbers war unrelated with the image quality?
Do I miss something big somewhere?

I guess that the DSP corrections are getting better and better. But does that mean gear producers renounced to perform optimal capture and few corrections in their devices?

I can understand that a 300$ point and shoot camera is designed with 3nm pixel size, cheap sensor, plastic lens and MASSIVE DSP corrections.
But what about top-end professional digital gear?

With film, I have a 100% control on gear, film, processing and almost a 100% understanding of each.

To me it is very frustrating to use or be forced to use a gear that I do not fully understand. (digital MF/LF devices)
Not knowing and not controling what happens in the magic box (DSP), not knowing the technical trade-offs that are made by gear producers on sensors is unacceptable to me.

So that is why I would like to start a discussion of this kind on my favourite photography forum.


I am aware that this topic is not 100% related with LF. But I didn’t feel like starting this thread in the lounge!
Moreover it is about current concern on photography. And my worry in this topic is top-end quality just as in my LF work and LF topics.
And finally I am curious to read the opinions of the experienced photographers and the optics experts roaming on that forum.

Regards,
CA.

PS : I hope my english isn’t too much of a pain to read.