From: P N Stenquist
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. 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. 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
The Sigma 10-20 comes in two versions f/4-5.6 & a constant aperture f/3.5.
I have the former and am quite pleased with it, although I'm still
learning when and how to use it to maximum advantage. A lot of people
badmouth Sigma lenses, but the build quality on this lens is rock solid.
I have the Pentax FAJ 18-35 that I consider a really sloppy lens, and
the Sigma is miles above it in quality.
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