Archived posting to the Leica Users Group, 1996/04/18
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>On Fri, 12 Apr 1996, Gary J Toop wrote: >>Thus, a >> thinner film base will have two effects: it will decrease the amount of >> diffraction, improving sharpness at least a little, and it will permit >> the direct passage of a little more light. This latter effect may be >> more significant if you are using a condenser rather than a diffusion >> enlarger, although I am not sure. The backing used with 120 film permits >> the use of a thinner film base, I believe. >> >> So, unless someone else out there has some reason to believe that >> that account is not correct, there is probably at least a slight >> difference between the sharpness of 35mm and 120 films which is due to >> the difference in thickness of their respective film bases. I am no technical man on this subject but from actual experience in the use of the 120 and 135 films, I have the following observations: (a) I've use the Kodak Gold 120 and 135 for experiment, when the 120 and 135 images are enlarged to the same ratio (not print size), the print made from the 135 image produces far better quality in terms of definition and sharpness. I know that this depended on many variables, the lens quality being a vital factor. But my ignorant guess is that the 135 emulsion is of better quality than that of the 120. This wild guess is based on the fact that 135 film is more and more accepted for commercial use and very enlargement is required so the film manufacturer will need to ensure that a good quality enlargment size is possible. On the other hand, the 120 is already 3 times the size of the 135, so given the enlargement is to the same print size, the quality is made up by the advantage of the larger film area. Therefore, the quality of the emulsion can be compromised. I know this is very non-sense guess but very actual in experience. (b) The question of light diffraction resulted from thickness of the film base is true. Anyone doing enlargement will know that whether the film is placed with the base up or down in the enlarger, a difference in the sharpness of the print is noticeable. TK Chan tkc@hkstar.com