Archived posting to the Leica Users Group, 2004/10/27
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]This may be possible but it seems like a lot of work for fun! I do know somebody who derived the transfer function for a valve amplifier and analogue pickup cartridge, programmed it into a DSP and had it as an option in his home brewed D to A convertor for CDs. It was quite fun to listen to AB comparisons. Frank --- "Douglas M. Sharp" <DouglasMSharp@netscape.net> wrote: > Hi Frank, > just a bit of lateral thinking - what would happen > if there was (is > there perhaps?) a method of limited > randomisation or random shifting of pixels within a > defined grid? Or is > this what happens with grain emulation > in PS?. Would we get a digital result > undistinguishable from analogue? > I'm thinking on the basis of experience with the > many interpolation, > noise reduction and signal enhancement processes > used > in geophysical processing (seismic data). Which, > when we get down to it, > is only another form of signal processing just > like image manipulation. For example we distinguish > between random > (digital noise/hiss) and ordered (artefacts) > interference in seismic > data, and all data are in more or less regularly > sampled 2 or 3D > coordinate systems, surely there must be some > applications also > applicable to photography. > An interesting test would be to take identical > images with digital and > analogue and subtract one from the other > to enable us to see exactly what and where the > differences are. Assuming > a digital resolution of the same order as the grain > density on film it > is conceivable that the analogue negative added to > the digital positive > would cancel out > those locations where there is data correspondence > (eg positive value + > corresponding negative value = zero) > and leave us with a "noise image" from which a > function for noise > reduction or signal enhancement could be > extracted with reasonable ease. > Either removing the digital "fingerprint" or adding > the analogue fingerpint > to an image to "analog-ise" any digital data set. > Taken further, this > could be used to give the film typical > appearance and character for any film type to a > digital image - Fuji, > Kodak whatever. > > Sorry to waffle on about what's probably of no > practical use at all, but > who knows......... > Douglas > > > > > Frank Dernie schrieb: > > > Hi Douglas, > > My point was exactly that, one does not produce > any new grains on the > > negative but unless there is an identical pattern > and number of grains > > on the print paper, with identical magnification > to that chosen in the > > enlarger, the print will not be identical to the > negative, and > > assuming more grains in the print paper than the > negative then there > > is some similarity with digital upsampling, though > it is random rather > > than mathematically defined. > > Frank > > On 27 Oct, 2004, at 00:16, Douglas M. Sharp wrote: > > > >> > >> > >> Frank Dernie schrieb: > >> > >>> Hi Phong, > >>> I completely agree. Since film is the most > digital of "analogue" > >>> media, in that it consists of discrete grains, > in a somewhat random > >>> pattern, but still basically so many grains per > square inch > >>> (depending on film). When the film is exposed > the grains are > >>> effected depending on colour, light intensity > etc but there are > >>> still a fixed number of grains. When the > negative is enlarged a new > >>> sheet of "analogue" material is exposed in the > enlarger. Unless this > >>> sheet of material has identical grain pattern > and number of grains > >>> as the original negative, and the enlarger lens > is perfect, the > >>> resulting enlargement has -must have- > interpolated information in it > >>> and is changed from the original. > >>> Frank > >>> > >> True enough but I think in the case of > analogue/film/negative we should > >> get away from the term "interpolated".In the > technical sense the > >> definition > >> is that a new, narrower, grid is constructed from > a grid of original > >> information. In the case of digital information > the interstices between > >> the existing > >> value grid are "filled-out" with new values > containing information from > >> the surrounding or neighbouring values. > >> The degree of influence (weighting) of the > neighbouring real data on the > >> resulting value is governed by processing > algorithms or simple matrix > >> filters. The simplest form would be to take an > equal proportion of each > >> of the four corner values of a grid to produce a > reasonable > >> approximation to what a real value might be at > the centre. More > >> complicated methods also take into account the > neighbouring groups of > >> values, these can be overlapped or weighted > (binning) to produce an > >> albeit less reliable but more realistic result > including trends within > >> the data.. > >> > >> In the case of a negative or film the more or > less random distribution > >> of grains shows no regular structure, the "data" > may "look" different > >> after enlargement > >> but the finite number of grains remains the same. > An interpolation per > >> definition at source doesn't take place in so far > that we are not > >> creating any new grains.. > >> Douglas > >> > >> > >> > >> _______________________________________________ > >> Leica Users Group. > >> See http://leica-users.org/mailman/listinfo/lug > for more information > >> > > > > _______________________________________________ > > Leica Users Group. > > See http://leica-users.org/mailman/listinfo/lug > for more information > > > > -- > Ihre bevorzugten Shops, hilfreiche Einkaufs-Hilfen > und gro?artige > Geschenk Ideen. 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