Archived posting to the Leica Users Group, 2014/02/22
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I was thinking about the event on the FE lenses where they focus at working aperture, and at focus, they open about a half stop during the AF portion of the program. Perhaps the camera compares the different depth of field at each aperture to determine final calibration? Most of the details needed to calibrate the lens might be stored in the lens' chip at manufacture. Judging from what I can see in the viewfinder when I have all the info turned on, the camera is capable of considerable computing power. On Sat, Feb 22, 2014 at 8:57 AM, Frank Filippone <red735i at verizon.net>wrote: > The camera is open loop.... meaning that there is no comparison upon which > to base a standard for what is in focus during calibration. In real world > terms, your eyes and brain decide what is actually in focus. So the > camera, > by itself, would not be able to do the calibration. ( why there really is > a > fine focus adjust feature in higher end cameras.. camera AF is adjusted by > the user to nail down the precise focus location. > > If you used a computer and factory "machines" to do the calibration, it > would be relatively trivial to imbed the calibration data into the lens ROM > and have the camera access that info, perform modification to the camera to > produce "correct" focus .... if the camera is calibrated.... which, even > in > the case of Leica, is not always correct.... > > In truth, the idea is a good one.... but requires the manufacturer to > calibrate each lens and embed the error-correcting-calibration, and each > camera body to a standard....and then to design FW to allow the access and > use of that data..... Read all of that as extra cost, and you get an idea > of why it has not been done yet.... > > If you go to the Sigma site, and read about their whoopee doo new lenses ( > I > think they are the ART lenses), you will read about a little gadget that > allows each AF lens + camera to have its errors embedded into the lens for > correction upon use..... The customer gets to do the work..... Cost is > pretty mild, work time is a few minutes per lens... It is pretty close to > your suggestion.... > > Frank Filippone > Red735i at verizon.net > > > -----Original Message----- > From: lug-bounces+red735i=verizon.net at leica-users.org > [mailto:lug-bounces+red735i=verizon.net at leica-users.org] On Behalf Of > Sonny > Carter > Sent: Friday, February 21, 2014 10:58 PM > To: Leica Users Group > Subject: Re: [Leica] OT - Sony Alpha 7R > > So how can you know how it doesn't do it and not know how it does it at the > same time? ;-) > > Sent from my iPhone > > Sonny Carter > http://www.SonC.com/look > > > > On Feb 21, 2014, at 11:56 PM, "Frank Filippone" <red735i at verizon.net> > wrote: > > > > You would need a reference calibration somewhere...and to be honest, > > the camera does NOT know what is actually in focus and what is not.... > > it only knows what should be in focus.... it is an open loop system.... > > > > Would you like to sit there at every F stop (and FL for a zoom) and > > calibrate the focus shift for every combination? > > > > This is a factory calibration, not a user calibration > > > > Frank Filippone > > Red735i at verizon.net > > > > > > -----Original Message----- > > From: lug-bounces+red735i=verizon.net at leica-users.org > > [mailto:lug-bounces+red735i=verizon.net at leica-users.org] On Behalf Of > > Sonny Carter > > Sent: Friday, February 21, 2014 9:49 PM > > To: Leica Users Group > > Subject: Re: [Leica] OT - Sony Alpha 7R > > > > Couldn't the camera calibrate the lens? After all, it is an optical > > computer; what is one more task added? > > > > Sent from my iPhone > > > > Sonny Carter > > http://www.SonC.com/look > > > > > >>> On Feb 21, 2014, at 11:37 PM, "Frank Filippone" > >>> <red735i at verizon.net> > >> wrote: > >> > >> That would require calibration of each lens ( maybe they all act the > >> same????)... > >> > >> I would think of this as a really good idea, but I also thought a R10 > >> was a really good idea...... > >> > >> Frank Filippone > >> Red735i at verizon.net > >> > >> > >> Frank Filippone wrote: > >> > >>> > >>> If you are focusing at working aperture, what advantage is there to > >>> native lenses? > >>> > >>> I'm not so sure Sony has this thought out...... > >> > >> For those who are interested in such things, native-mount lenses will > >> allow shutter-priority and program exposure modes, and AF. > >> > >> Another way to handle focus shift would be to program the lens to > >> tell the camera how much shift there is at various apertures. Given > >> this would be a native-mount lens the camera would know what aperture > >> the lens will be using. > >> > >> Doug Herr > >> Birdman of Sacramento > >> http://www.wildlightphoto.com > >> > >> > >> > >> > >> _______________________________________________ > >> 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 > > > > > > _______________________________________________ > > 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 > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information > -- Regards, Sonny http://sonc.com/look/ Natchitoches, Louisiana 1714 Oldest Permanent Settlement in the Louisiana Purchase USA