Igor Roshchin wrote: > Mon Aug 27 09:58:53 EDT 2007 > William Robb wrote: > > >> ----- Original Message ----- >>> From: "David J Brooks" >> Subject: Re: Wedding photography >> >> >>> I have proven to my self over an over, if i'm going to do indoor >>> flash, the SB80DX and D2H are the only way to go for me. More >>> consistant results. >>> >>> Sorry Pentax wedding folk.:-) >> I've had no luck at all with Pentax's flash control over the years. From the >> LX and it's refusal to fire the flash in fill situations to the istD and >> it's really bad TTL control to the K10 and it's klunker flash interface, >> I've just never liked using pentax camera controlled flash. >> I think the people who are happy with it have never used a good flash >> control system such as Nikon's. >> > > I liked the combination of ZX-5n+AF500FTZ in TTL mode. > Not a perfect combination but good enough. > I never had that much experience with the automated flash control system > of Nikons. > > If my understanding of how the TTL metering works is correct, > I suspect that the DSLR introduced a new, almost "fundamental" > (although, probably technologically solvable) problem: > due to the highly reflective sensors, the measurement of the > much higher intensity reflection during the flash burst : > a) requires a higher dynamic range meter, and > b) depends more on the exact way the light bounces back from > the object and from the sensor, -I think they do some sort of > extrapolation in the electronics - to estimate when the flash > needs to be turned off. > Thus, TTL metering in DSLRs is less accurate. > That's why, I suppose, they have to come up with more complicated > ways, like P-TTL. > > I wonder though, why the metering is still done via reflection from > the sensor (is that the case?), and not by including some exposure > metering sensors on the sensor chip? Or am I wrong and it is already > implemented? > > For those (like me) who is interested to understand how various *TTL > metering schemes work the following pages may be helpful: > General ideas (and Nikons specifics at the end): > http://www.moosepeterson.com/techtips/flash.html > Nikon: http://www.planetneil.com/nikon/flash.html > Canon: http://www.bobatkins.com/photography/eosfaq/flashfaq.htm > Comparative table for various systems: > http://www.photozone.de/3Technology/flashtec6.htm > > I didn't find a comprehensive page for Pentax flash system > (but I was not looking hard for it, as they were more clear to me). > > > Igor > > >
With the exception of the *istD, DS(in TTL mode) and Fuji S2 Pro, all digital flash systems are entirely pre-flash based and do not use light reflected off the sensor to determine flash exposure. Traditional TTL-OTF flash is more accurate than preflash-based flash, but the latter is much easier to achieve with digital, and allows for the wireless flash capabilities that have so many enthralled. -Adam -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net