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| p.1 #7 · Canon 7D - M + Auto ISO the best mode for sports + BIF? |
I think I'm understanding where the OP is coming from, however I don't have an answer for him.
Say there is a shaded area on a baseball field, maybe by one of the bases. however, as the base runner moves from one base to another, the light increases or decreases a considerable amount. If a player is running from 2nd to 3rd base, 2nd base is in the sun, 3rd is in the shade, the camera is going to compensate the shutter speed greatly if set in aperture priority. when the player starts at 2nd, the SS is 1/800 @ 2.8 ISO 100. As he runs to third, he enters the shaded area and the camera adjusts the shutter speed, SS becomes 1/400 @ 2.8 ISO 100. At 1/400, the runners limbs will have plenty of motion blur, but at 1/800 the player would be mostly frozen.
Same situation, Auto ISO this time. The player starts running, the SS and aperture are manually set this time, so when the player starts at 2nd, the SS is 1/800 @ 2.8 ISO 100. When the player enters the shaded area, the camera now bumps the ISO rather than slowing down the shutter speed. SS is still 1/800 @ 2.8 but the ISO is now 200.
In this situation, the keeper rate would increase using auto iso in manual exposure mode, rather than manual iso and aperture in aperture priority mode.
Gonemad: when you mentioned "30% of shots in the sequence are blurred while pictures just before and right after are in focus, even though ZoomBrowser showed the focus dead center on the target" I think you're referring to motion blur rather than an oof subject. If your shutter speed is all over the place, some of the shots in the sequence you took may have motion blur rather than being out of focus.