Jens, My understanding is that in TTL mode, the Matrix mode exposure evalution is working for the *ambient* portion of the light metering, not for the flash metering. P-TTL allows an integrated preflash/ambient exposure evalution based on both metering capabilities.
I could be wrong, I'm certainly no expert on this stuff, but that's my understanding. It makes sense as the Matrix metering evaluation is completed before the mirror swings up, since the meter sensors' light is piped through semisilvered bits of the mirror into the sensors at the bottom of the mirror box. Godfrey --- Jens Bladt <[EMAIL PROTECTED]> wrote: > BTW. If it didn't, linking AE to Focus Point wouldn't be > possible for flash > photography, would it. > My test indicate that the area exposure differences due to > different > focusing distance, caused by choosing different (close or far) > focusing > points. I guess linking AF to Foucus point means more > attention to the > metered values in the parts of the matrix patern, close to the > chosen AF > point. > > > Jens Bladt > mailto:[EMAIL PROTECTED] > http://hjem.get2net.dk/bladt > > > -----Oprindelig meddelelse----- > Fra: Jens Bladt [mailto:[EMAIL PROTECTED] > Sendt: 17. februar 2005 07:50 > Til: pentax-discuss@pdml.net > Emne: RE: *istDS built-in flash overexposure problem > > > Matrix works with TTL: According to the EXIF ibfo avaliable in > the INFO > menu, TTL flash will use matrix/pattern metering (*ist D), > when an A or post > A lens is used at "A"-setting. > > Jens Bladt > mailto:[EMAIL PROTECTED] > http://hjem.get2net.dk/bladt > > > -----Oprindelig meddelelse----- > Fra: Godfrey DiGiorgi [mailto:[EMAIL PROTECTED] > Sendt: 17. februar 2005 00:43 > Til: pentax-discuss@pdml.net > Emne: Re: *istDS built-in flash overexposure problem > > > My understanding is that P-TTL allows the camera to take a > flash > reading and use the full matrix exposure evaluation system, > including whether you've linked the AF point to the exposure > evaluation, where TTL flash only gives access to the CW > Averaging meter pattern's exposure setting. > > I don't know which one will prove to give the best exposure > with > the greatest consistency, but from a purely technical point of > view I'd consider the P-TTL flash system as being more complex > or "advanced" compared to the TTL flash system. > > Godfrey > > > --- Nick Clark <[EMAIL PROTECTED]> wrote: > > It seems to me that so called advanced P-TTL is a cut down > > version of proper TTL. It cuts the flash off a a > predetermined > > time based on the preflash exposure measurement, rather than > > cutting it off due to measuring it during the actual flash > > exposure. > > > > > __________________________________ > Do you Yahoo!? > Yahoo! Mail - Easier than ever with enhanced search. Learn > more. > http://info.mail.yahoo.com/mail_250 > > > > __________________________________ Do you Yahoo!? All your favorites on one personal page – Try My Yahoo! http://my.yahoo.com
