Archived posting to the Leica Users Group, 2000/11/02
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]There are a few strands of arguments mixed up after my original post. Let me try to entangle and clarify them. And I apologize for being partly resonsible as I was not clear enough, I am afraid. First the basic point: I stated that in silverbased 35mm photography a resolution of 40 lines was enough for god quality/handheld imagery. I still stand firmly behind this statement. 40 lines times 24mm times 40 lines times 36mm equals 1.3 million image points. For those with a historical archive, we can look at Barnack's article about why he selected the 24x36mm format. And you will find the identical reasoning. Barnack arrived at a maximum count of 1 million image points as the norm for leica photography. Incidentally 40 lines per mm give you image points 1/40mm small, that is image points of of 0.025mm. As we all know the image points on the negative are assumed to be points with a diameter of 0.03mm (the circle of confusion). And Barnack used the diameter of the CoC in his calculation. So we may safely state that the 1.3 million image points in a 35mm negative are assumed by the inventor of the format to be good enough for normal situations. OF COURSE; current emulsions have much higher resolutions and when we use 200 lines/mm as the optimum (corresponding to the 100 lp/mm of the best leica lenses), we get a much higher count: 24 x 200 x 36 x 200 = 34.5 million image points. Back to the proposition. The 1.3 milion image points are 960 x 1440 image points. By calling them picture elements, some were quick to assume that the 960x1440 grid or matrix of image points is identical to a 960 x 1440 sensor array (CCD). This however is NOT the case. And by identifying my grid of image points with a small scale CCD of indeed very modest quality, the matter gets very confusing. See part 2