On Dec 10, 2003, at 2:26 PM, James Turley - Sky Image Lab wrote:
> You got some serious "bokeh" image stabilized
> Fluorite glass here, my man
>
> Canon EOS 10D 6M DSLR at 100 ISO
> 300mm f/4L IS USM + 1.4x EF TeleCoupler Extender
> giving effective focal length = 1.8 x 1.4 x 300 = 756mm
The "focal length multiplier" for a 10D is 1.6, not 1.8. So if he's
using a 300mm lens with a 1.4x converter then the effective fl is
"only" 672. But note that the image has been cropped so in a sense the
focal length is ever longer.
There is much confusion about the "focal length multiplier" for DSLRs.
The lens is not affected. All that's really happening is that a
smaller portion of the image is being recorded than would be the case
with a sensor the same size as 35mm film. When you then crop it
further with Photoshop the resulting "effective focal length" isn't
particularly meaningful.
-- Bill Arnett bill@No-Spam http://nineplanets.org/ Emerald Hills CA USA 37 27 N 122 15 W