Ken,
> Is there any functional - i.e. visible - difference between negative > FEC and Vari-power? In other words, given the same exposure mode, is > dialing in -1 stop of FEC the same as leaving FEC at zero and using > 1/2 power? E-TTL(II) uses the evaluative exposure circuits of the camera to determine the exposure. E-TTL-II takes also distance information (if available) into account. With (M)anual mode, you set a fixed power and the flash will ALWAYS fire at that specific power setting. Flash exposure depends on f/stop (lens aperture) and distance. If you set FEC to -1, the ETTL system will expose the subject at -1 stop even if you walk to it, get further away or open-up/close-down the diafragma (within the limits of the flash power). With Manual, first of all, you will need a flash meter (or the digital histogram method) to determine the correct exposure. Let's say that (like in your example) that you set 1/2 power to get the subject with -1 stop flash exposure; now, if you get closer and want to maintain the same exposure you have to dial down the flash power or increase the f/stop to compensate for the variation in distance. >My limited understanding of E-TTL also causes me to > wonder how much this changes in various exposure modes, especially Av. In (M)anual mode, the flash will output the given amount of power (1/1,1/2,1/4,1/8...) independently of the camera mode used. I hope that's also clear from the previous paragraph. > With my current 420EX/30D or Elan 7 setup I can get 2 stops of > negative FEC, so one advantage of the 580EX would be the ability to > go all the way down to 1/128 for macro fill and the like, if these > two are really related. 1/128 = Nope. That's just minumum manual power, but in E-TTL the flash can output even less power than that! With the 580EX you can get -3 stops FEC, but I don't know how that helps in macro situations (-3 would be only for some catchlights) > Any other comments on what real-world, noticeable, pluses there would > be to the upgrade also welcome. I do realize the 580 has a higher > GN, of course. But the 420EX is an amazing little unit, I've never > been disappointed in it. But now that I have a DSLR I'm wanting to > experiment a lot more - what would the 580 do that the 420 can't? I don't have a 420EX so I can't answer to that question. I upgraded from a 550EX and I'm very satisfied with the 580EX. Main 'highlights' (pun intended :-) are: 14mm diffusion panel, white catchlight panel, very fast recycle times, a friendly user interface (the wheel behind is the best thing that Canon could do!) I can even set one slave with 1 hand instead of needing two hands for the 550EX. the 580EX can be a wireless master controller. >what would the 580 do that the 420 can't? The obvious: putting out more light -Wireless master - 14mm coverage - manual mode - stroboscopic mode - automatic zoom compensation for DSRL cropping - wanting another 580EX - a hole in your pocket :-) -greetings, Gerard. * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
