It is pleasantly surprising to me, as an old photographer who still does most of my work in manual modes, how amazingly accurate many of the automatic features on today's DSLRs are- the can work well! Through the lens metering and exposure control is certainly a handy tool for both amateur and professional photographers, especially when fast paced impromptu shooting is required. There are times when I am happy just being an “appliance operator” rather than a finite technician having to figure out and mentally calculate so many exposure issues. There, are times, well most of the time, that I need more precise control over the aesthetics of my lighting and that oftentimes demands the use of manual modes or what I call “modified automatic modes”.
My advice to many photographers who are learning or looking to improving their flash techniques to delve into some of the “old school” manual methodologies such as; flash power outputs (watt-seconds and ECPS ratings), guide numbers, flash to subject distances, the inverse square law, the angle of incidence theory, basic portrait lighting, lighting ratio, reflector and bare-bulb usage, hand-held exposure meter techniques, flash fill in out of doors and available light scenarios, and off the camera, bounce and multiple flash lightings.
If we become overly dependent on automatic operation, we loose finite control over the aesthetics of out imagery and there becomes a sameness in all our flash work, especially if the flash unit is just about “bolted” down to the hot shoe atop the camera.
Understanding exactly how basic flash photography works gives us more appreciation and insight into what out automatic features are doing for us- some of it is truly amazing! We also learn to “fool” our automatic systems by manipulating them, thereby giving us the tools to enable more customized effects, moods, and variations. We also learn to avoid some of the intrinsic problematic aspects of flash usage, the gremlins such as subject failure and flat lighting and “black hole backgrounds”. Subject failure occurs when the readings from the internal metering system are gathered in the wrong zone within the frame and serious, usually overexposure, issues result. Flat lighting lacks dimensionality and is a product of unmodified and non-directional on the camera flash usage. Underexposed (black hole) backgrounds and overexposed foregrounds, again are the result of flat-on-the camera flash and poor placement of the flash head on the camera which also causes distracting shadows on backgrounds and walls.
Even in auto modes, we can create better lighting and more control by purposely “fooling the system” and telling it what we want it to know! We can change the ISO settings, change the shutter speed to admit more ambient light and there are many modifications that we can introduce to create many variations. In a two light hand-held system, I have been know to place my hand over the on-camera light and just let a “sliver” of light seep out through my fingers to alter the lighting ratio without having to move further away from the subject and sacrifice my composition or take the time to remove the fill light from the camera.
I hope this helps. Ed