on 25/11/01 2:29 pm, Malcolm Stewart at [EMAIL PROTECTED] wrote: >> The close focus is 31cm Malcolm. The new lens also has full-time manual >> focusing. >> >> Tim > > Hi Tim, > Thanks - I assume that's from the film plane mark? > I've just measured the various distances with my original non-USM EF 100 > f2.8 macro which also has internal focusing, but which I understand has a > different construction to the USM version. > At 1:1, > lens length front to back 15.2cm; > lens front-subject 11cm; > lens hood-subject 7cm; > film plane-subject 31cm - same as yours, I assume > At 1:2, > lens length front to back 13.0cm; > lens front-subject 20.5cm; > lens-hood-subject 16.5cm; > film plane-subject 38cm. > > When I first got the lens I used it without any hood, and thought that my > slides were a little lower in contrast than my other slides, even though the > filter was coated, and clean; so I've always used a short lens hood on it > since. No complaints now apart from the lack of FTM. Perhaps I should have > tried it without hood or filter. > > As an afterthought I've dug out my X-700 with my Vivitar 90 f2.8 macro and > done the same measurements: > At 1:1, > lens length front to back 17.8cm; > lens front-subject 13cm; > film plane-subject 36cm; > At 1:2, > lens length front to back 13.5cm; > lens-front-subject 22cm > film plane-subject 40cm > The Vivitar lens isn't an IF lens so keeps its 90mm focal length throughout, > and its front element isn't so deeply recessed as the Canon. > > Malcolm Stewart Milton Keynes, UK >
Hi Macolm, Yes, the distance is measured from the film plane. Inspired by your example I did the same measuring experiment (though its a rough job!). With the USM EF 100mm f/2.8 lens at 1:1 Lens front-subject c15cm Film plane-lens front c16cm (no lens hood-I don't have one) Film plane-subject 31cm At 1:2 Lens front-subject c24.7cm Film plane-lens front c16cm (still no lens hood!) Film plane-subject c40.7cm The Canon lens is of course IF, so doesn't change its length. The front element is flush with the lens front (unlike my old Nikon 105mm, which was deeply recessed) I also dug out an old Vivitar macro, this time a 1970s vintage Series One 90mm f/2.5 in Nikon fit, which I mounted on a Nikkormat FTn. (This lens focuses normally down to 1:2 and has a 1:1 adapter which mounts on the rear end.) At 1:1 Lens front-subject 12.5cm Film plane-lens front 22.7cm (again no hood) Film plane-subject 35.2cm At 1:2 Lens front-subject c21cm Film plane-lens front 18.2cm Film plane-subject c39.2cm The Vivitar extends greatly in length when wound out to the max. The front element is recessed perhaps 2cm. Tim * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
