Bob Meyer wrote: >According to Chuck, there's a "sanity check" (My >words, not his) done on the reflectance results, and > if the exposure seems unreasonable, then distance >information is used. Of course, I have no way to >verify the claim, but Chuck doesn't seem like the sort >to make things up. This information was provided in >an exchange on the Compuserve photo forum, btw, where >Chuck used to spend a lot of time. (Maybe he still >does, but I don't.)
Once again, Canon fails to document automated system behavior. I want my system to behave consistently or at least give me an option to make it consistent. I've been happy with Canon flash systems up to and though the 540EZ model, but have not tried an EX flash with E-TTL yet, so I can't offer opinion on the EX/D30/D60 issues. Doesn't the older A-TTL mode fire a pre-flash to gauge the distance, not the reflectivity? But any time you use Av or TV for auto-fill flash or a bounce angle on a 540EZ, it goes from A-TTL to plain old TTL, which measures reflectivity. I wish Canon would just document everything so that we know what to expect, or make it consistent or give us a way to cancel automated compensations. E.g. I always keep my Custom Functions set to turn off the Automatic Flash Reduction algorithm on my A2/540 EZ, after having read the old Speedlite Reference Guide, because I can't stand not being confident about how the system will behave. I just dial in flash exposure compensation based on my own judgement and experience, and I get great results. Nothing beats experience and judgement, not even a Nikon! I don't always trust the evaluative metering, either. If I doubt the built-in ambient exposure readings or see extreme contrast subject matter, I spot or partial meter the crucial elements of the subject matter. If I know ahead of time that I won't have time to do a lot of spot metering (e.g. wedding candids), then I use print film for exposure latitude and tweak the printing exposure and contrast as needed. Bottom line: there is no auto exposure or flash system in the world that gurantees 100% accuracy in all situations. All that being said, I wish Canon got subject distance for flash exposure from all lenses, if for no other reason, than to be consistent body to body, flash to flash, lens to lens. I remember an old rumor that Canon can't use distance info from lenses to calculate flash exposure with guide numbers because another maker (Nikon?) owns the patent on the idea and Nikon won't grant or Canon won't pay for a license to use the patent. General use of guide number/distance/aperture flash exposure algorithm is hardly patentable, but whoever owns the patent for using distance info from lens electronic contacts must have filed a clever patent application claiming that distance automatically read from lens is a state of the art advancement over manually reading distance from the lens barrel markings. :) Cheers, David Heller * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
