----- Original Message ----- From: "Ken Durling" <[EMAIL PROTECTED]> ............................ if I take a reading _in > P mode, using Partial metering - (I have 800 speed film in the camera > right now) of the bookcase across the room with the flash turned off, > I get 1/60 @ f/2.0. If I turn on the flash and let it cycle up, I get > 1/60 @ f/4. This is without firing any pre-flash. Now as I > understand it, when I actually fire the shot, E-TTL is going to do yet > another calculation, and determine the flash duration. But 1/60 @ f/4 > will still be valid, right? What I'm a little confused about is how > the camera knows to choose f/4 when the flash goes on......
Hi Ken, What you describe above seems to be quite correct. The camera in P mode is actually choosing 1/60 as the lowest shutter speed for hand holding in a low light situation, while f4 is the aperture to match at a given flash output - I have no idea what the actual built in calculations are. If you moved your reading to a slightly better lit spot I would expect the camera to reduce your aperture before it starts to increase shutter speed ie 1/60 @ f5.6. The reading you get in A or T mode of 1/60 @ f2.0 is the correct ambient reading without flash, which if fitted would act as a fill flash only. I sounds like you are understanding it right but looking at it too closely. Regards, Tim www.timmunro.com.au * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
