Adobe Flash Question:

Most nature and scenic professionals use -1.3 to -1.7 stops for their fill flash setting because they are trying to do one thing only: increase shadow detail (an alternate way of saying this: decrease overall scene contrast). Why? Because exposures for slide film need to be biased to the brightest object in the scene (i.e., overexposure of slide film is VERY bad). Since film has a limited dynamic range it can record with reasonable detail, if you set your exposure to put the highlight at the white point, you often lose shadow detail. The purpose of the fill flash, therefore, is to raise the film's response curve at the shadow point without further blowing out the detail. The -1.3 to -1.7 values are often just enough to pull another "stop" of useful shadow detail into an exposure without adding unduly to the highlight exposure. Films like Velvia are especially troublesome,