P N Stenquist wrote:
On Apr 12, 2010, at 8:48 AM, Keith Whaley wrote:
Bong Manayon wrote:
Thinking of ...
1. Pentax DA 12-24
2. Sigma 10-20
3. Tamron 10-24
Am not into fish-eyes so those options are out. Any votes for or
against any of those listed above?
Thanks!
Bong
I don't think those focal lengths are 35mm-equivalent numbers. I
suspect they're double ~ such as the Pentax DA 12-24 is really like a
35mm lens of 24-48mm focal length.
Nice wide angle-to-normal lens, but hardly a fish-eye...
First, the conversion factor for angle of view is 1.5.
Was Bong talking about a specific camera? I know we were talking digitals,
but, I thought each camera had it's own conversion camera. In my limited
experience, which does NOT include DSLRs, most cameras differ a little as to
what their 35mm equivalent is.
I avoid the uncertainty by referring to the owner's manual for each camera.
They always mention it...
So the 12-24 has the same _angle of view_ on an APS-C DSLR
as an 18-36 would have on a conventional 35 mm frame.
Cropping factor, or what I call the telephoto effect, brought on by the size
of the sensor. In other words, the ratio derives from how much smaller the
DSLR's sensor is compared to 35mm film size.
See:
http://www.minasi.com/photos/dslrmag/
However, the focal length is 12-24. That
doesn't change, regardless of the format. Furthermore, it's not a
fisheye on any format. It's a rectilinear lens. In other words, the
optics make the verticals as true as possible given the size of the
elements and the constraints of physical science.
Paul
Quite so. Thanks Paul.
keith whaley
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