TTL shooting modes (automatic exposure evaluations that are synced across the camera, lens and flash system) are great for capturing basic exposures of a scene, but these automatic camera evaluations restrict you from using light in more creative ways. Meter readings also can be very wrong, especially when working in tricky environments with mixed lighting situations or when using modification tools like bounce cards, reflectors, diffusion panels and other gear.
Learning to understand manual settings will give you extended control over flash output while also providing consistent results that you can modify as needed for the best image, even when using extra tools that will affect your total light output.
Even when using a TTL mode, you still have a lot of control over output. Most flashes allow you to adjust exposure value via a +/- button with a lightning bolt, usually by a 1?3- or 1?2-stop. Locking in flash exposure compensation also will let you change position without affecting the amount of light produced by the flash.
Shooting at full power will deplete batteries the fastest and requires the longest recharge times between bursts. You don’t always need full power, however, and choosing to shoot at lower output will increase battery life and recycle times dramatically.
Distance will affect the light throw, as well. Light falloff equals the square of the distance to the light source, which is known as the inverse-square rule. In other words, a subject that’s moved to twice the distance from a light source will require four times the amount of previous light for the same exposure. So moving your flash forward or backward is another great way to add or reduce light as needed, and light output is exponential as you get closer to the subject.
MODES AND FEATURES
All flagship flashes and a number of more basic models offer specialty modes that will give your flash extra artistic license. Flashes provide a lot of leverage when working with motion blur, for instance.
Slow sync combines a burst of light from the flash with a slower ambient exposure for sharp subject details that employs motion blur in the background. Second curtain, or rear-curtain sync, refines the effect with a sharp, flash-frozen subject and a blurry background with a motion-blur effect that naturally follows the subject in the frame.
Most cameras have a maximum shutter sync speed set between 1?160 and 1?250 sec. At faster shutter speeds, a black band is noticeable in the exposure because the shutter curtains are exposing only a thin wedge of the sensor at the time of the flash burst, which lasts for a shorter duration than the total exposure. High-speed sync circumvents this problem by emitting a number of lower-intensity light pulses that will gain you faster shutter speeds and, consequently, shallower depth of field in well-lit situations.
Achieving faster shutter speeds also will give you the ability to lower ambient exposure levels in your image while exposing correctly for your subject with the flash, kind of like a neutral-density filter that will affect ambient light conditions without drastically changing the exposure of your subject.
TAKE YOUR FLASH OFF OF THE CAMERA
Off-camera flash is the first step toward giving your two-dimensional images a three-dimensional pop. Taking the camera off-axis reduces the familiar high-contrast, heavy vignetted look that’s created by singular light sources with highly directional lighting. Sidelighting and angled lighting will enhance the contours of your subject, while bounced light will be more diffuse and natural.
This is why many flash models offer an internal bounce card, diffuser and swivel abilities for bouncing light from ceilings or walls. You still have to trigger a flash once you’ve removed it from the hot-shoe, and there are a few different methods to do this, each with its own advantages and disadvantages.
Optical infrared communication between the camera and flash is a common internal feature built into higher-end flash models by manufacturers because it also gives TTL abilities, though this requires a direct line of sight that’s also limited by distance.
You also can use a simple camera sync cord (with TTL abilities) or a PC cord (which is more affordable, but lacks TTL communication); however, even with longer cords, your flash distance is severely limited by the tether length of the cord.
Wireless radio-frequency (RF) transmitters from Tamrac, PocketWizard, RadioPopper and others will give you the most leverage as you can control multiple flash units in groups at very large distances as well as through obstacles.