Archived posting to the Leica Users Group, 2004/10/15
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I think all you guys have yet to hit the nail on the head on this one. "crop factor" is a meaningful term because if you are using a 100mm lens on a 35mm cameras system you have lots of bodies to choose from and they all are normal 35mm 24x36mm format bodies. But if you put that lens on a body with a CCD or film even which is APS-c sized as most digital is and which is 25.1x16.7mm you have a 1.5 crop factor and a smaller needed image circle and a smaller format diagonal. Which means you're not using the full 43.3mm diameter of the image circle the lens is projecting. (24x36) Your only using a 30.1 image circles worth. (aps-c) Your lens in effect is has the horizontal coverage of a 150mm lens which is about 14 degrees. Normally you'd get 20 degrees with a 100mm lens on a 24x36 format. What makes my theory questionable perhaps is the fact that there are plenty of so called digital 35mm format lenses which DO have a 30.1mm image circle. I just got one. The Sigma 55-200 DC. But if I'd use this lens film you'd get plenty of vignetting. Unless it was APS-c film or half frame film. Then the term "crop factor" kind of falls apart. The DC lens is doing what it was designed to do. A mental translation is needed. But no cropping can be found anywhere. we still need to realize that a 100mm lens on an APS-c format digital body is giving the angle of view that a 150mm lens on 24x36 is giving us that we are used to. But again nothing is being cropped. Just like nothing is being cropped when we are using a 150mm lens on a 6x6cm format camera and we want to know what this is in 35. It's a 100mm lens or darn close. We do this because most of us started with 24x36 and have done by far most of our work with 24x36. And that's how we think. That's the language we speak in our brains. "translate that to 35 please?". We don't refer that as a "crop factor". We refer to that as the "yea but what is that in 35mm buddy!?" factor. Speak in terms that we can understand please!!!! Again let me make a plea for film camera bodies to come out with this format. To work with all these cute compact sharp as heck, cheap "digital" lenses. Call them "digital film" cameras they'll be bound to sell one of two of them. 72 on a roll it won't feel like your wasting money of expendables like it can when you shoot film and you're used to digital. And T grain or tab grain technology makes this 25.1x16.7mm size perfectly viable. Which is close enough to 18x24 half frame to make that size viable I'd hope. A friend of mine is bringing his rare I think Leica half frame (72) to the LHSA meeting in Williamsburg the week after next. I'm all excited to see it! Mark Rabiner Photography Portland Oregon http://rabinergroup.com/