> > From: "Russell Kerstetter" <[EMAIL PROTECTED]> > Date: 2006/03/21 Tue PM 09:15:41 GMT > To: [email protected] > Subject: crop factor vs. telephoto factor > > I mostly lurk here, however I do have a question that I have had > answered is two different ways, and always by someone who knows more > than me. > > The Pentax dslr's have a 1.5 crop factor, so this means either: > > 1) A 50mm focal length is still a normal perspective only with the > sides cut off, because the sensor is smaller than a 35mm negative, and > so the recorded image is simply smaller because of that. > > ....or.... > > 2) A 50mm focal length is now a medium telephoto perspective, with the > same effects, with regard to image compression (from front to back) > and depth of field, in the same way that on a large format camera a > 50mm focal length is a wide perspective. > > So.... > > I feel like there is some concept about the mechanics of a lens that I > do not understand, but both explanations make sense to me, so I don't > know. > > Russell
I think of it in terms of the output. If you make a same-size print of the view from both systems, the 35mm film print will cover more and will therefore appear to be wider angle. The APS digital print will cover less but, because it is the same size print as the 35mm, has to be enlarged further and looks more telephoto. You get the same effect if you project the images to the same size. The change of image dof compression is minimal compared to the crop/telephoto effect. m ----------------------------------------- Email sent from www.ntlworld.com Virus-checked using McAfee(R) Software Visit www.ntlworld.com/security for more information
