Jostein wrote: > Please someone correct me if I have got this wrong; I'm going to attempt a > coherent (don't laugh) description of my own understanding here... > > IMO, the number of pixels can be considered to be a function of > 1. the properties of the CCD used to capture the light, and > 2. the software to interprete the captured data. > > I'm not sure I know all the properties involved, but at least there is the > number of physical pixels, and their size (density), and the Bayer algorithm > involved to reconstruct a colour image from the physical pixels. > > To consider a 35mm equivalent, assume a 36x24mm CCD. How many pixels do we have > to put into a 36x24mm CCD to match the resolution power of a film? > > For simplicity, let's assume that this is equal to the size of film grains that > we can measure in a microscope. When that is known (i haven't got the > number...), we can compare that to the pixel size on the chip. I am pretty sure > that eg. Provia 100F grain size is smaller than current pixel size in eg. > *istD. > > And here's a problem; there is a physical limit to how small pixels can be > before they start to behave erratically. The size used in the *istD is thought > to be quite optimal, if I have understood this right. > > If the above is correct, the optimal 36x24mm CCD is one with approximately the > same pixel density as the *istD has, which would amount to ca. 14 Megapixels. > > I don't know if 14 Megapixels in 36x24mm is even close to the grain size of > ProviaF, but let's assume that it was...:-) > > Those 14 Mpix must be subjectet to Bayer interpolation before we can see a true > RGB image. The interpolation will tend to smooth out details that are smaller > than the smallest cluster of pixels used in the interpolation. I'm not sure > exatly how this affects the final image quality, but I suspect that this is the > reason why skin tones and blue skies look smoother with digital, while grassy > fields or tree branches and twigs look smeared out. Especially in low-contrast > situations. > > So, even if 14 Mpix was equivalent to film grain number, CCDs would be less able > to hold detail (I think this is where the Foveon concept excels over Bayer > interpolation). > > This means that you would need more pixels per area than you have film grain per > area to record the same level of detail. If film grains can be made smaller > than CCD pixels, film will win hands down. And that's no matter what format you > compare. > > Another discussion is whether the lenses exist to give you full value for either > recording media. If the practical resolving power is less than pixel/grain > density, the difference between film and CCDs is suddenly not _that_ important > any more. > > > So Nenad, > I'm not at all sure I know any better than you, I'd rather learn than teach. I'm > just testing my own grip...:-) > > Cheers, > Jostein > You're too modest Jostein! You've put together a very coherent and logical analysis.
Regards Nenad
