How did you calculate the effective focal lengths? Paul On Dec 9, 2006, at 10:20 PM, Digital Image Studio wrote:
> Since I don't often shoot long lenses one of the most attractive > things about SR to me is the potential to make more use of available > light in my macro photography. However thinking about this and the > relevance of FL in the degree of correction that's applied got me > shinking about effective FL at close subject distances. > > Studying my macro lens arsenal it appears that at their maximum > magnification apparent focal length can be quite different to their > infinity FL. > > My A*200/4 Macro appears to be effectively 137.5mm at 1:1 mag, so the > change in diagonal AOV through the focus range is from 8.08° at > infinity to 11.74° at 1:1 magnification. > > My Voigt Lanthar 125/2.5 is effectively 95mm at 1:1, my FA50/2.8 is > 48.75mm at 1:1 and my A50/2.8 is 55.5mm at 2:1 > > Given this knowledge I can dial in the effective FL on my manual > lenses so that SR is optimized when I'm working at or close to 1:1. My > question is does the SR system compensate for FL change when using > later lenses where manual input of the FL is not available? Obviously > with the shorter FL lenses it of minimum significance as FL doesn't > change dramatically but with longer lenses where shake is magnified it > would be preferential if the system either compensated for FL change > or allowed manual FL entry. > > I know it's being critical but I didn't spend all that cash on my > macro lenses with a view to not getting the very best out of them ;-) > > -- > Rob Studdert > HURSTVILLE AUSTRALIA > Tel +61-2-9554-4110 > UTC(GMT) +10 Hours > [EMAIL PROTECTED] > http://home.swiftdsl.com.au/~distudio//publications/ > Pentax user since 1986, PDMLer since 1998 > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
