Ryan K. Brooks wrote: > > On Sun, 27 Aug 2006, Godfrey DiGiorgi wrote: > > >>On Aug 27, 2006, at 1:30 PM, Ryan Brooks wrote: >> >> >>>It appears to be a crop of a wide angle lens, which it is. >>> >>>In particular, informal head and shoulders shots look a bit odd if I'm >>>close to the subject. The shoulder may seem enlarged if I'm taking a >>>profile, for example. Whereas a 50mm would compress this distance >>>more. >>> >>>I thought I would be at home with the 31mm limited on the D, but >>>using a >>>wide angle lens to achieve a normal-length crop is a bit wonky to >>>me. I >>>still like it, I wish I was using a 50mm focal length instead of a >>>31mm >>>lens cropped. >> >>??? >> >>I don't know how you can tell the difference. The lenses' rendering >>qualities might be slightly different with respect to out of focus >>elements and rectilinear correction, but with regard to field of view >>and perspective: if the field of view is the same, the perspective >>will look the same. > > > The field of view is the same, but that doesn't say anything about the > transform taking place optically. The image from 50mm crop of a ~31mm > lens != 50mm > full frame. Try it. You can really see it when you're framing, and it > makes for weird magnification of things close to the lens. > > I'm not talking about bokeh or anything esoteric. Try it. Cropped > focal length isn't the same as focal length. Not interested in a debate, > > -R
The difference you're seeing is at most because the 31mm on Digital is closer to a 45mm lens on 135 film than a 50. Compare a 35mm f2 and a 50 and you'll see the same thing. Perspective is totally due to distance. Field of view is based on focal length and format size. Otherwise everything comes down to the unique character of the lens design. Same field of view and same distance will provide the same perspective. That's simply physics. Note I've tried this, at least on my Nikons (I didn't own a 35mm lens when I had my *istD). The 35mm on my D50 and the 50mm on my F3 look the same. -Adam -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
