At 06:51 AM 9/6/2002 +0300, you wrote: >We all know that focal lengths of digital cameras are given as 35 mm. >equivalent focal length due to small size of the ccds. I have seen in >lots of places, that this is explained as "this is the focal length that >gives the same magnification as a 35 mm. camera". > >I may be missing something but I think that the only equivalency is in >relation to the field of view, not magnification. It is NOT Optical Magnification. It IS mathematical magnification. If a 50mm lens is considered a 1X lens on a 35mm camera, a 100mm lens, a 2X, a 300mm a 6X, then if a 35mm lens is considered the "Normal 1X" lens on a digital camera, then a 50mm lens is a 1.5X lens. A 300mm lens is a 9X lens on a D1 family camera. Light hasn't been blown up at the film plane, a 300mm lens is still a 300mm lens, it just means something different to digital, in the D1's case, its a 9X lens with regards to filling its "Full Frame". Anothre way to view this mathematically is to take a full frame 35mm negative. To make an 8x10 (or 8x12 to keep the 3:2 ratio right) means you need to pretty much enlarge it 8 times. A film frame the size of the CCD of a D1x at 24mm wide instead of 35mm wide would need to be enlarged 12 times to make that same 8x10/8x12 print, or the same as blowing up the 35mm negative to 12x18 and cropping an 8x12 middle out of it. Regardless, there is a 1.5X increase in the magnification at print time, if the CCD were film. Now here is where the fun is. With film, you get a surface area to work with. In most cases you have to enlarge that surface area to make it useful which means magnifying the negative using enlarger optics to get the desired output. Digital is different. A D100, Nikon's 6 Megapixel camera produces a 3008x2000 pixel image. If your output device is a 300 dots or pixels per inch device like many photo printers are, the D100's image without any magnification (i.e. resampling) is a 6.667 x 10" print. Conversly the native print size of 35mm is roughly 1x1.5". This is one reason that the D1X, D100 and Canon D60 are able to compete with medium format cameras on the output quality side. So many MF shooters gave up their MF gear to start using digital (wedding shooters in particular) . This is why an 8x10 from a D1X or D100 printed on a Fuji Frontier on Fuji Crystal Archive paper will rival a Kodak Portra 160 print from a 120 negative printed on the same paper. Rob -- Rob Miracle Photographic Miracles 203 Carpenter Brook Dr. Apex, NC 27502 http://www.photo-miracles.com
