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Hasselblad 56x42mm 60 mpix
Noons said:
On Dec 29, 10:44=A0am, Peter Irwin wrote: Every grain in film is either on or off. You get the impression of continuous tone because there are a huge number of grains. Completely false, of course. There is no such thing as "on and off grain" in film, that is a demented and stupid conclusion from an online site run by a moron who hasn't used film in decades. It is always possible that I may be wrong about practically anything, but I certainly didn't get this from an online site. I got it from books. I'm sure you have seen books with electron micrographs of developed film (some very old books show less clear optical micrographs) to explain how the image formation in film works. The last time I looked at these books it seemed that a grain either developed (became a speck of metalic silver) or it didn't and was dissolved by the fixer. If you know better, I would be glad if you could show me or tell me where to look for imformation. Peter. -- |
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Hasselblad 56x42mm 60 mpix
wrote,on my timestamp of 30/12/2008 7:27 AM:
It is always possible that I may be wrong about practically anything, but I certainly didn't get this from an online site. I got it from books. I'm sure you have seen books with electron micrographs of developed film (some very old books show less clear optical micrographs) to explain how the image formation in film works. The last time I looked at these books it seemed that a grain either developed (became a speck of metalic silver) or it didn't and was dissolved by the fixer. If you know better, I would be glad if you could show me or tell me where to look for imformation. Let me have a go. Please note that I am over-simplifying like crazy, otherwise this would be a veeeery lengthy post. Film grain is not the same as a pixel. The two couldn't be more different. There are quite a few sites - and books - who have tried to equate the two, but it is completely wrong. This particular post: http://photo-utopia.blogspot.com/200...nd-clumps.html should set you on the correct path to determine for yourself the truth. I also have a pointer to a document from Kodak on electron microscope photos that confirm this, can post it later if you are interested. There are also heaps of discussions on the subject in sites populated by folks who actively use film and digital, like APUG or the rangefinder forum. Each grain is not a pixel. You get much more than one pixel from a single grain speck, with full definition and separate resolution. Colour is slightly different but essentially the same principles apply. In simplified terms - all sorts of nuances with colour film, for example - each grain is a crystal, which is made up of many thousands of molecules, each of which indeed IS the rough equivalent of what we call a pixel in digital terms. Even then, you still have a number of atoms in each molecule, not the whole of which will be turned to silver. Hence the gradual - analog? - gradation of the result, as opposed to the digital pixel on-off, discrete nature. And the whole lot is random in spatial distribution, as opposed to the regular patterns of a digital sensor. Which also explains why anti-alias sensor filters are needed for digital and not with film. If you allow me a rough analogy, a single grain in an emulsion will NEVER be simply on or off, because it is made up of many thousands of "switches", which won't be all on or off. Unless one has gone for complete block-out or blow-off, of course! Oh, slightly off-topic: what you see as "grain" in b&w, for example, is not. It is the space BETWEEN grains, which shows up dark after reversed scans. That is what most people see as "grain", and can easily be eliminated with noise reduction software or adequate lighting during the scan. If you take the care of examining a negative with a 40X microscope for example, you'll notice the difference immediately: clearly defined detail INSIDE each "grain". But you need to be using a "high grain, high accutance" developer like Rodinal. Modern low grain developers act by slightly dissolving the silver in grain, thereby reducing somewhat the "clump" nature of the spaces between each grain. They also slightly lose accutance in the process by altering the contents of each crystal, some more than others. But all that is waaay beyond the point here. |
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