Flash allows for the subject and surrounding elements in the photo to be highly illuminated, allowing us to see as we would normally see an object in bright daylight. This daylight allows the ISO or filmspeed of a camera to be dropped, preferably between 100-400. At these low ISO settings, colors will be rich and saturated unlike photographs taken with natural light in shady areas or at night. In these darker areas, without flash, the ISO must be increased (between 400-1600) to allow the sensor to become more sensitive to light, but problems can arise with color desaturation, low shutter speed (blur) and film grain; what is commonly refferred to in digital imaging as “noise”.
Flash Guns or “Speedlights”, unlike studio lights, are highly portable and when placed on the camera’s hotshoe thoroughly integrate and communicate with the camera: things like ISO, subject distance and shutter speed thus allowing the photo to be consistently tuned to an appropriate and hopefully pleasing look. It’s the pleasing look that is subjective and is directly related to how the photographer directs the light. It is this lack of direction from the photographer that is often the source of failure resulting in horrible looking shots with flash.
The idea is to get pleasing results, not harshly lit centers or heavily outlined or darkened edges. How do we accomplish this?
Never point the flash directly at your subject – you wouldn’t shoot your family or friends with a gun and a flash gun is no exeption! Instead, direct the flash towards a ceiling at an angle that will go up and fall back down to your subject and directly behind them so the environment they are in is also illuminated for context.
Soften the light, known as Diffusing
This is done with translucent covers or with reflectors that redirect and then scatter the light forward. This is also done with portable bounce cards, mini soft-boxes for the flash, or translucent domes or other types of diffusers.
Spread the light
Done by keeping the flash head programmed for a lower focal length or by multi-bouncing. A beauty dish is a good example of a multi-bounce on a small scale.
Use the Appropriate Speed
Flash Guns or “Speedlights” off of the camera, along with studio lighting or those triggered remotely, take special consideration concerning shutter speeds. With speedlights attached to the hotshoe, the light retains the “Speed” of the camera shutter all the way up to those shooting extremely high speeds – up to 1/8000 or one eight thousandth of a second! This is how rain and water drops are fantastically captured in mid-splash. Off the camera, along with studio lights, the shutter speeds have to remain low and no higher than 1/250 or one two-hundred and fiftieth of a second. One can’t go too low either, or blurring will occur. So the low end of the shutter range in flash should be no lower than 1/40 or one fortieth of a second. The best way to enforce the camera stays within the appropriate shutter range is to 1.) Lock in the range in a camera menu if capable or 2.) Shoot in manual mode! That “M” can be mighty big, I know as it’s this second option that scares people and this is where the separation of a professional photographer from a casual shooter begins.
When on the hotshoe, remember the “speed” of “speedlight” becomes active. With higher shutter speeds we can stop motion. This is how sports photography can be done successfully, but often can’t due to high school and arena restrictions: flash could inhibit an athletes performance.
Night time photography
There are two settings that should be considered: 1.) Non-tripod or walking shots and 2.) Tripod use.
The walking shot as I like to call it involves high ISO values (1600-6400), low aperture values (f/5.6 – f/1.4) and low shutter speeds (1/125 – 1/40).
The tripod shot is the best. It partially tricks the camera into a daylight application for the night! On a tripod, ISOs should be kept low (100-400), the aperture at a higher value (f/7.1 – f/16 max). Shutter speeds are long – ranging from 3″ to 15″, or better read as 3 seconds to 15 seconds. This type of shot will give the photographer low film grain, a sharp image, light traces from traffic, and can also result in flares or “stars” from every point of light at 8″ (seconds) or longer shutter speeds.
Hotspot – The center point of the flash reflected from the subject.
Falloff – Used to describe the rate at which the center point of the flash darkens towards the outer edges of the image. Heavy falloff indicates an image has a bit of darkness or thicker shadows to it. Light falloff indicates an image is well illuminated throughout with barely noticeable or normal darkness or shadows.