Can someone tell me if this is normal or not? Here\'s the situation.
I\'m in a room with windows. I\'m using a MKIII in Tv mode with the shutter speed set to 300. There is a 580 EXII mounted in the hotshoe, and the 580 OFF, I use the exposure lock button to expose for the outside sky. Using center point focus, and spot metering, the camera indicates f22. If I lock the exposure, and take the shot, the sky is perfectly exposed.
Now I turn the 580 ON. When I point the center focus point to the sky, the camera no longer indicates an f stop of 22, but abouut f13 instead. I take the shot again, and the sky, of course, is blown out. Even though I\'m using metering linked to center point spot, it seems that once I turn the flash on, the ambient reading, instead of being a spot reading, has defaulted to some sort of average reading.
In other words, using center focus point, spot metering, focused on the same point, I get two very different AMBIENT readings by simply turning the flash on or off.
I\'ve used both the 580EX, and the 580EXII, with the flash set for both ETTL and manual, with the same results, so I\'m sure it is not a flash/mode problem
Is this normal, or perhaps a quirk with my camera?
I don\'t think my 40D behaved this way, although I can\'t really test it, since I just sent it in for cleaning.
Can someone tell me if this is normal, or not? Here\'s the situation.
I\'m in a room with windows. In Tv with the shutter speed set to 300 and the 580 OFF, I use the exposure lock button to expose for the outside sky. Using center point focus, and spot metering, the camera indicates f22. I lock the exposure, take the shot, and the sky is perfectly exposed.
Now I turn the 580 ON. When I point the center focus point to the sky, the camera no longer indicates an f stop of 20, but abouut 13. I take the shot again, and the sky, of course is blown out. Even though I\'m using center point spot, it seems that once I turn the flash on, the ambient reading, instead of being a spot reading, has defaulted to some sort of averae reading.
In other words, using center focus point, spot metering, focused on the same point, I get two very different ABMIENT readings by simply turning the flash on or off.
I\'ve used both the 580EX, and the 580EXII, with the flash set for both ETTL and manual, with the same results, so I\'m sure it is not a flash/mode problem
Is this normal, or perhaps a quirk with my camera?
I don\'t think my 40D behaved this way, although I can\'t really test it, since I just sent it in for cleaning.
Can someone tell me if this is normal, or not? Here\'s the situation.
I\'m in a room with windows. In Tv with the shutter speed set to 300 and the 580 OFF, I use the exposure lock button to expose for the outside sky. Using center point focus, and spot metering, the camera indicates f22. I lock the exposure, take the shot, and the sky is perfectly exposed.
Now I turn the 580 ON. When I point the center focus point to the sky, the camera no longer indicates an f stop of 20, but abouut 13. I take the shot again, and the sky, of course is blown out. Even though I\'m using center point spot, it seems that once I turn the flash on, the ambient reading, instead of being a spot reading, has defaulted to some sort of averae reading.
In other words, using center focus point, spot metering, focused on the same point, I get two very different readings by simply turning the flash on or off.
I\'ve used both the 580EX, and the 580EXII, with the flash set for both ETTL and manual, with the same results, so I\'m sure it is not a flash/mode problem
Is this normal, or perhaps a quirk with my camera?
I don\'t think my 40D behaved this way, although I can\'t really test it, since I just sent it in for cleaning.
Any thoughts appreciated.
Thanks,
Harvey
Nov 22, 2008 at 09:16 AM
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