Archived posting to the Leica Users Group, 2015/11/04
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Subject movement trumps wide open aperture. from my iPad Sonny Carter > On Nov 4, 2015, at 9:36 PM, Frank Verizon1 <red735i at verizon.net> wrote: > > All true , but nothing trumps the sccuracy of a fully wide open aperture > > Frank Filippone > >> On Nov 4, 2015, at 10:22 PM, Geoff Hopkinson <hopsternew at gmail.com> >> wrote: >> >> Yep didn't forget that. I was attempting to explain that if the lens was >> already at the shooting aperture (like an M lens for example) it may be >> that an EVF can still display a bright enough image for focussing (that is >> your EVF brightness is controllable). >> Focus at the shooting aperture of course defeats any focus shift (for >> example from f/1.4 to f/4). Much depends on what you are shooting I >> imagine. >> Just played with this on the XT1 and the Summilux 50 ASPH down to f/8. >> >> However personally I have never found DoF preview sufficiently precise or >> particularly useful in any camera at all from the 70's forward. I may be >> an >> outlier there ;-) >> >> >> ---------- Forwarded message ---------- >> From: Frank Filippone <red735i at verizon.net> >> To: "'Leica Users Group'" <lug at leica-users.org> >> Cc: >> Date: Tue, 03 Nov 2015 22:35:51 -0800 >> Subject: r >> Yes, all true.....but you forget that DOF is, for example at F8, greater >> than at F2. So focusing is much less precise without auto stop >> down.......... >> >> Frank Filippone >> Red735i at verizon.net >> >> >> Do I have it right that the desire for automatic diaphragm control is for >> focus at maximum aperture then stopping down to shooting aperture at the >> moment of exposure? >> >> Doesn't the use of the EVF potentially permit the finder brightness to be >> controlled? If the lens is stopped down (ie not operating with auto >> diaphragm) of cause the image arriving at the sensor is what is used for >> focussing. So the desire for auto diaphragm control comes from the OVF >> systems? >> >> M lenses of course are already being employed with the initial SL units in >> the field. >>> >>> You can get autoexposure only if the camera knows what the open >>> aperture and the taking aperture are. If the lens does not generate >>> those info, then some kind of manual system is needed >> >> Autoexposure with TTL metering in apertured-preferred mode is simple with >> no >> auto-diaphragm, no data other than light, ISO and shutter speed is needed. >> >> With TTL metering and an automatic diaphragm the camera needs to know the >> difference between open aperture and working aperture. It does not need >> to >> know what the actual open aperture is or the actual working aperture, only >> the difference. Any other data is extra and can be used for the user's >> convenience, but is not required for autoexposure function. >> >> >> Cheers >> Geoff >> http://www.pbase.com/hoppyman >> >> _______________________________________________ >> Leica Users Group. >> See http://leica-users.org/mailman/listinfo/lug for more information > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information