Nope, that's simply not the case. The mechanical coupling is much smaller than in-lens motors can be.
For a good example compare the Nikkor 20/2.8 AF-D to the Canon EF 20/2.8 USM, or even the Nikkor 50/1.8 AF-D to the Canon EF 50/1.8 II (which is plain old DC micromotor drive). Putting the motor in the lens makes it bigger, a lot bigger in some cases, particularly when ring-type USM drives are used (As you have the motor surrounding the optical group in that case). Both the Nikon's are half the size of the comparable Canon lenses, in fact the Nikons are only slightly larger in AF-D form than the optically identical AI-S manual focus versions. The DA limiteds are going to be screwdriver AF for a long time. John Francis wrote: > SDM lenses can be *smaller* than lenses with mechanical AF coupling. > > On Fri, Feb 23, 2007 at 10:52:03PM +0100, Thibouille wrote: >> Maybe not that soon. >> DA Limited won't get SDM because of size, I think. >> >> 2007/2/23, John Francis <[EMAIL PROTECTED]>: >>> On Fri, Feb 23, 2007 at 01:00:40PM +0100, John Whittingham wrote: >>>> On Wed, 21 Feb 2007 23:57:53 +0100, Thibouille wrote >>>>> http://forums.dpreview.com/forums/read.asp?forum=1036&message=22150903 >>>>> >>>>> -- >>>>> >>>>> Thibault Massart aka Thibouille >>>>> ---------------------- >>>>> *ist-D,Z1,SuperA,KX,MX, P30t and KR-10x ;) ... >>>> Ooooh! SMC Pentax-DA* 300mm f4 ED IF SDM, yes please, gimme, gimme 8) >>>> >>>> John >>> I'm sure it will be. Quite apart from anything else, SDM offers the >>> most advantages with larger, heavier lenses; a larger motor can be >>> fitted, providing more responsive focussing. >>> >>> But, in any case, I very much doubt that we'll see any new lens >>> designs that don't have SDM - that's the way of the future for Pentax. >>> What will disappear is the old mechanical screwdriver autofocus. >>> We'll eventually see camera bodies that won't even have an in-body >>> autofocus motor, and will only autofocus with SDM lenses. >>> The first such body (no more than five years from now) will almost >>> certainly be a low-end entry-level model, where the price savings are >>> significant. But I expect it will gradually spread throughout the >>> range, until screwdriver AF goes the way of the aperture simulator. >>> >>> >>> -- >>> PDML Pentax-Discuss Mail List >>> [email protected] >>> http://pdml.net/mailman/listinfo/pdml_pdml.net >>> >> >> -- >> Thibault Massart aka Thibouille >> ---------------------- >> K10D,Z1,SuperA,KX,MX, P30t and KR-10x ;) ... >> >> -- >> 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
