William Robb wrote: > ----- Original Message ----- > From: "Toralf Lund" > Subject: Re: TTL, P-TTL, other *TTL's and DSLRs (Was: Wedding photography) > > > >> Something I've been wondering about lately, is which is better of a >> traditional auto-mode and P-TTL. I mean, which is greater of the error >> in the pre-flash based prediction and the inaccuracy resulting from >> using a sensor not measuring through the actual lens (and making >> calculations based on a "theoretical" aperture)? Any thoughts? >> >> Maybe the best result might be achieved if you used an external sensor >> to control the actual flash operation, but included a through-the-lens >> pre-flash measurement to collect knowledge about the actual exposure >> conditions? Is anyone doing that? > > Once I left Nikon, I discovered that basic auto flash was more accurate than > TTL flash. I happen to have a very accurate auto flash though, I expect a > cheap auto flash will be as inaccurate as the rather useless Pentax in body > flash control. > I suspect that the best way to get body controlled flash would be to > transmit distance information from the lens rather than use reflective > information from the sensor. > > William Robb > >
Which is how Canon E-TTL II works(E-TTL primarily used reflectivity under the selected AF point), and is also used by P-TTL and Nikon's D-TTL and i-TTL systems. -Adam -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
