Makes sense, thanks. I'm starting to get brave enough to work on some of the newer bodies, the more I know the less I have to guess. ;-)
Don > -----Original Message----- > From: Godfrey DiGiorgi [mailto:[EMAIL PROTECTED] > Sent: Thursday, January 05, 2006 6:43 PM > To: pentax-discuss@pdml.net > Subject: Re: MicroPrism ist-D Focus Screen is here! > > > Regards the ambient sensors, this information was passed from the > folks at Tekade.de on the DPReview forum when someone asked about > metering errors with their custom split-image prism viewfinder > screen. Just like the screen you bought, their screen works fine in M > and CW modes but needs a correction in S mode, for exactly the same > reasons. > > For a TTL flash sensor to work, it has to be in the mirror box > (because it operates at exposure time). I doubt that Pentax would put > two different flash sensors in the body to support TTL and P-TTL > separately, so those are in the mirror box. > > Godfrey > > On Jan 5, 2006, at 4:34 PM, Don Sanderson wrote: > > > Godfrey, could you tell us where you found this info? > > We were discussing it the other day, it would be nice > > to have a reference source. > > I know the older meters pretty well but the > > technology has passed me up. ;-) > > > > Thanks! > > Don > > > >> -----Original Message----- > >> From: Godfrey DiGiorgi [mailto:[EMAIL PROTECTED] > >> Sent: Thursday, January 05, 2006 5:30 PM > >> To: pentax-discuss@pdml.net > >> Subject: Re: MicroPrism ist-D Focus Screen is here! > >> > >> > >> The Spot pattern sensor reads off the focusing screen and is not > >> exactly aligned with the optical center of the viewfinder optical > >> system, thus the metering discrepancy. > >> > >> CW Averaging and Matrix meter patterns are read from sensors in the > >> bottom of the mirror box and should cause no discrepancy in meter > >> readings at all. I believe that the P-TTL/TTL flash sensors are co- > >> located with the CW Averaging and Matrix metering sensors. > >> > >> (Far as I'm aware, this is correct information for D, DS, DS2 and DL > >> bodies.) > >> > >> Godfrey > >> > >> On Jan 5, 2006, at 2:17 PM, Don Sanderson wrote: > >> > >>> I tested with the spot pattern. > >>> I'll try again with the others but the 1/2 stop really isn't > >>> something I'm too worried about. > >>> > >>>> Which meter pattern are you using? Matrix, Spot or CW Averaging? > >>>> > >>>>> The new screen requires you to use -0.5 exposure compensation > >>>>> to get the same meter readings as the original screen. > >>>>> IOW the camera thinks the scene is 1/2 stop darker than it is > >>>>> and will overexpose without compensation. > >>>>> This would indicate the meter is behind the prism as others > >>>>> thought and not behind the mirror as I thought. > >>>>> > >>>>>> Could you elaborate on that a bit? How does it increase > >>>>>> exposure? Does it > >>>>>> require a greater exposure time for the same results as the > >>>>>> original > >>>>>> screen, or less? > >>>>>>> > >>>>>>> The new screen seems to increase exposure by about 1/2 stop. > >> > > >
