Archived posting to the Leica Users Group, 2004/10/26
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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 >