Archived posting to the Leica Users Group, 2000/06/01
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Inbox for mikescarpitti@yahoo.com Yahoo! - My Yahoo! Options - Sign Out - Help Mail Addresses Calendar Notepad From: "Erwin Puts" <imxputs@knoware.nl> | Block address To: <kodachrome@kjsl.com> Date: Thu, 1 Jun 2000 20:25:30 +0200 Subject: [Kodachrome] Some data to bring sanity to this list again Reply-to: kodachrome@kjsl.com Add Addresses Lenses for photographic systems are corrected primarily for the spatial frequency range of 5 to 20/30 lp/mm. And it is wellknown that the 10lp/mm are instrumental in giving the psychological sharpness impression. As the MTF curves can be cascaded (multiplied with each other), it makes sense to look at the MFT data of films in the same range. Here are the figures for 5, 10 and 20lp/mm K25: 115, 120, 100 K64: 110, 115, 95 K200: 110, 115, 95 E100VS:105, 100, 98 for blue light and 100, 85, 60 for red light. This is the first time that a manufacturer gives data for different wavelengths and that may be very significant. All other films also respond differently to different wavelengths. Fuji Velvia: 110, 115, 100 Fuji Provia: 110, 110, 100 If I now take an excellent lens, like the Leica Apo-Summicron-ASPH which has 100% for 5 lp/mm, 95% for 10 lp/mm and 90 lp/mm at optimum aperture we get these composite figures for K64: 100x115, 95 x 115 and 90 x 95 = 115, 109, 86 For Provia: 110, 105, 90 An excellent Canon lens (1.2/85) will give MTF data at 10 and 30 lp/mm (so I have to interprete a bit here) 10lp= 95% and 20lp= 85% Using Provia again: -, 105 and 81%. Using K64: -, 109, 81% Anyone wih a calculator can do his/her own sums. What this tells you is this: the percentage difference at the 20 lp is significant between the Canon and Leica lens. It does also tell you that a Provia film with this Leica lens is as good as the Canon lens with K64. Basing yourself on only these data leaves out many a significant variable and is detrimental to a real and serious assessment of the parameters involved. Why is it that K-films do give more sharpness impression and and improved definition of finer detail. The K-films are grain based, while the F-films and generally all E-6 films are dye cloud based. A dye cloud has smaller area than a grain clump, because of inhibitors, but also decreases the acutance effect, which is then artificially (chemically enhanced). Still grain based films (like any B&W film) have beter acutance and so will record finer details till the grainines overcomes the detail rendition. The superiority of K-films is the combination of edge sharpness (acutance), its grain structure, its three layer (versus 16 layer) and its high MTF values. All in combination! You cannot single out one elemenent and make a case of it. The whole is more than the sum of the parts. I have no intention to be an evangelist and the case for religious converts is over since the middle ages (even if there is one person thinks otherwise). Outstanding imagery is possible with Canon, Nikon, Leica etc and E-6. One caveat: the very fine qualities of K-films can be appreciated if the lens is accurately focused, expertly exposed and the camera is vibration free during the exposure. The acutance effect is diminished when there is movement blur involved. In my view the qualities of K-films reside more in the grain based, three layer structure than is a carelees juggling of figures. And a last warning: not every Leica lens is on the Olympic hill. So the statement that leica and K-films are giving a special dimension to 35mm photography has at least to amended to the question which leica lens you use. Agin sweeping generalisations are counter productive to a purposeful discourse of the merits of the K-films and how to exploit their potential. Erwin ===== You must have Adobe Acrobat Reader 3.0 or later to read the Acrobat PDF version of my resume attached. If you do not have Acrobat reader, you can get it free from Adobe. You can download Adobe's Acrobat Reader software from this link which will allow you to view and print the PDF. Please refer to: http://www.adobe.com/prodindex/acrobat/readstep.html#reader The Adobe Acrobat PDF format allows you to view this formatted document electronically on most computers. The freely available Adobe Acrobat reader is required to view and print PDF files. __________________________________________________ Do You Yahoo!? Send instant messages & get email alerts with Yahoo! Messenger. http://im.yahoo.com/