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02/15/2004 03:23:20 PM · #1 |
Does anybody else use their 10D with custom function 4 (C.Fn 4) set to 1? Just a couple weeks after I got the camera, I enabled this setting and have never looked back since!
With CF4 set to the default setting of 0, half-pressing the shutter button activates auto-focus and automatic exposure metering. If you are in "One Shot" AF mode and using evaluative metering, as soon as focus is locked, the exposure is also locked (which is why the * icon lights up in the viewfinder). If you are using the servo AF modes or center or partial metering, the exposure is not locked with a half-press of the shutter; you can see the exposure change as you recompose your shot (as long as you're not in "M"anual mode, of course!) So with the servo focusing modes or center or partial metering, the (*) button on the back of the camera functions as an "exposure lock" button, allowing you to find an object you want to meter off of, and lock that exposure.
When you set CF4 to 1, the star (*) button on the back of the camera and a half-press of shutter button swap functions: (*) becomes the "Auto Focus Activate" button, and a half-press of the shutter allows you to quickly lock in an exposure around the active focusing point. Being able to lock in exposures is great when you are shooting a backlit subject, for example. And if you are in one of the servo focusing modes, you can always keep the (*) button depressed with your thumb to keep the AF tracking active.
I like having AF on the (*) key, and adapted to it very quickly. To me, it provides a little bit more control on the photographer's part about when to focus and when to lock the exposure. But there is another advantage to setting CF4 to 1 (or 3) that is useful when using E-TTL flash. This may be worth investigating if you are finding it hard to get consistent flash results on the 10D. (I'd also suggest reading this tome of information, and the electronic version of Canon's Flash Work brochure).
When using a flash and a lens that is set to "AF" (auto focus), a large area centered around the active focusing point receives more emphasis than the remainder of the 35 metering zones when calculating flash exposure. (Check page 75 of the 10D manual to see a diagram of the 35-zone metering area. Be sure to note that there is a significant portion of the frame -- namely, all around the edge -- that is never metered at all.) However when a lens is set to "MF" (manual focus), all 35 zones receive equal weighting for flash metering in E-TTL.
And here's the benefit of setting CF4 to 1 (or 3): when the (*) button is not being pressed, the AF system is not active and all 35 zones receive equal weighting for flash metering in E-TTL, just as if the lens was set to manual focus. When the (*) button is pressed, the E-TTL flash meter reading is weighted to the active focusing point as described above. Accordingly, CF4 can be useful to help control the E-TTL flash metering pattern. Keep the (*) button pressed when you depress the shutter button fully to weight the E-TTL flash metering pattern to the active focusing point, release the (*) button prior to shooting to average the E-TTL flash metering across all 35 metering zones.
Note the difference between settings 1 and 3 of C.Fn 4: When set to 3, you disable the ability to "lock" the exposure, so metering is always determined the instant the shot is actually taken. You still focus by half-pressing the shutter, but the (*) button now starts and stops AI Servo AF.
Hope this this is interesting to some of the other 10D shooters out there. (If this is over your head, continue to learn and someday, hopefully it will become clear!) |
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02/15/2004 03:42:34 PM · #2 |
Eddy, thanks for the very clear discussion of this. I have left C.fn 4 set to "0", since I find using the * button to lock the exposure pretty natural. I prolly will leave it that way for now, but your observations regarding E-TTL metering are very interesting. If/when I decide to spring for the 550EX flash, will certainly play around with C.fn 4!
Thanks Again.
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02/15/2004 07:44:56 PM · #3 |
i have my c.fn 4 set to "3 AE/AF, no AE lock ". it works pretty good for me because i can recompose the scene while the metering continues.
i do tend to change every now and then though. |
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02/15/2004 08:36:29 PM · #4 |
Eddy,
Clear message and good post. Thanks for the info. I will be testing this over the coming months.
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