The reflective tape used on fire gear has the characteristic of reflecting light at nearly any angle.
Evaluative metering, the default mode for Canon flash, keys off the highlights which is why you are getting under-exposure. Try setting flash metering to \"average\" via CF.n which should produce results similar to the average metering auto sensor on the Vivitar.
Manual will be more consistent and predictable. With a bit of testing you\'ll be able to quickly determine the power levels needed at various distances. Stick with one f/stop and set flash zoom manually to a fixed setting such as 24mm so the only variable is power level.
But if you look on the back of the flash in M mode you will see there is an indicator which shows the distance at which flash exposure will be correct which takes into account aperture and flash zoom setting. All you need to do is estimate the distance and then turn the power dial until the indicator on the back of the flash is over that distance.
Chuck
Dec 15, 2008 at 12:08 AM
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