Archived posting to the Leica Users Group, 2000/04/10
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]the Summicron Modern tested out at 105 l/mm was a 50 Dual Range Stephen Gandy. Stephen Gandy LRZeitlin@aol.com wrote: > I have been asked in private e-mails where my estimate of 9 megapixels as the > digital equivalent of the 35 mm frame comes from. Here it is: > > In an oft quoted article "How Sharp Can You Get" published in the October > 1976 issue of Modern Photography the editors used heroic measures to squeeze > 100 lines/mm out of a number of high quality 35mm camera 50 mm lenses. The > best performance was given by an older Leica Summicron (7 element) which > reached 105 l/mm on High Contrast Copy film. Most lenses, including the > Summicron reached 96 l/mm on Tech Pan. Faster films scored lower. Images on > Kodachrome II peaked at 80 to 86 l/mm. To stay on the conservative side, I > estimated the maximum usable resolution as 100 l/mm, fully realizing that > most lens-film combinations would be less. > > The area of the 35mm frame is 864 sq. mm. Each sq. mm at 100 l/mm resolution > requires 10,000 pixels, the total being 8,640,000 pixels. Hence the 9 > megapixel estimate as the digital equavalent of 35 mm. Using 24 bit color > information, this works out to a file size of about 26 MB. Moderate JPEG > compression at 1:4 will reduce this to a more manageable 6.5 MB file size. > > While this is a reasonable approximation of the amount of information stored > on a 35 mm frame using today's methods, it is far lower than the maximum that > could be stored given advances in lens/film technology. The theoretical > resolution of an f2.0 lens is 882 l/mm in green light. This works out to 672 > megapixels and a file size of over 2 billion MB. Don't hold your breath > waiting for Leica to offer lenses of this quality soon, however. All of the > twentieth century efforts in camera lens design have only improved resolution > for normal lenses by a factor of two. > > The LUG tends to place undue emphasis on resolution as the essential quality > of imaging. In my youth, I worked for a Boston newspaper that never used > finer than a 65 line halftone screen in its daily edition. We photographed > sporting events with 4x5" Speed Graphics, not because of the high picture > quality available from the large negative but pecause it could be fully > processed in two minutes in concentrated developer and fixer and a printing > plate could be made while the negative was still dripping wet. The paper was > proud of the fact that it often had a paper on the streets showing the > winning goal in a Celtics game before the crowd filed out of the Boston > Arena. > > Today most of us watch hours of television whose images are formed by fewer > than 0.3 megapixels or stare at computer screens which deliver their images > at about 0.5 megapixels. A cheap low end digital camera can meet those > requirements with ease. The vast majority of the world's pictures are never > enlarged to a size greater than 4x6". A 1.5 megapixel camera and a basic ink > jet printer will suffice. Timeliness, availability, flexibility and cost per > image are often more important than resolution and tonal depth. A picture in > the hand or on a electronic display screen is worth more than a dozen much > finer images on a roll waiting to be developed. > > LarryZ