Toralf Lund wrote: >>> [ ... ] >>> >>> >> 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. >> > 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? > > - Toralf > >
My experience is that unless you have a fair bit of rather light or dark colours in the centre of the scene, Auto Thyristor flash is as good as any preflash system except i-TTL (P-TTL, E-TTL II) and significantly better than plain E-TTL on a Canon DSLR (E-TTL works much better on film as it uses OTF and preflash metering, while being preflash-only on digital, E-TTL II was a badly needed upgrade for Canon). Nikon has led the pack in TTL flash capabilities since the introduction of the FA in 1993 and i-TTL seems to work much more reliably than the other systems (including Nikon's aborted D-TTL system used with the DX-series flashes and D1/D100/D2 cameras, D2's are also i-TTL capable). I suspect this may have a lot to do with Nikon's more complex metering system as preflash-based systems allow Nikon to take advantage of their superb ambient metering technology for flash as well. Your suggestion is actually similar to Canon's old A-TTL system, although in the opposite manner (A-TTL uses a flash sensor to measure preflash and TTL-OTF during the exposure). -Adam -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
