Flash seems to be the Achilles’ heal of many beginner photographers, and why wouldn’t it be? A quick Internet search confronted me with jargon such as “TTL”, “Inverse Square Law”, “Fall off”, “Sync Speed”, “Guide numbers” to name only a few.
Flashes or speedlights, as they are also known, produce instant light, which is only visible for a millisecond. Instant light is not difficult to understand or use, just different from ambient or constant light and once the basics are understood, you might even fall in love with photography all over again.
This blog is aimed at the absolute beginner, but hopefully contains more than enough information to have you take the flash out your camera bag – there is a reason you bought it after all… Flash light is extra or fill-in light. It comes with the advantage that we can control it, from its strength to its direction; we can aim it and modify it until it is exactly how we want it. We can control the shadows it makes on our subject and in doing so we can bring out the best in our subjects shape and or features. It has the advantage that it can freeze movement.
It is light that is easy and convenient to modify, but lets clarify some of the jargon first.
Flash is just a light that we can aim.
Direct Flash: The flash is aimed directly at the subject. Direct flash is flat uninteresting and unflattering light and often results in harsh shadows or red-eyes.
Bounce Flash: Bounce flash is the good stuff. By tilting the flash head up, in order to bounce the flash from the hopefully white ceiling or wall (side or rear), improves flash photography by creating beautiful soft light which will wrap around your subject to enhance shape. It is a basic principle of light that a bigger light source produces softer light. The entire ceiling area becomes the light source which is much bigger than the tiny flash. For an added bonus, the problem of red eyes is also eliminated.
Bounce card: The small white card some flashes have, allows the light to continue up unhindered to the ceiling when you use bounce flash. The small card adds a little direct front light (filling shadows, making them a bit lighter) and the card adds catch light in the eyes. Some photographers call this forward spill. The bounce still does the lighting and makes the shadows on the subject.
On-camera Flash and off-camera flash: On camera-flash simply refers to an external flash that can connect directly to your camera. It does not necessarily require that the flash be physically mounted on your camera to operate, as on-camera flashes are often used off-camera.
Flash is a light we can control…
TTL (Through-the-lens) flash automation: The camera, in conjunction with the camera’s metering system controls the flash out-put. The camera emits a few small pre-flashes. The light returning through the lens is measured and this value is used to calculate the amount of light necessary for the actual exposure and the flash out-put is adjusted accordingly.
Manual flash: The camera does not control the out-put of the flash, the photographer does by adjusting the settings in fractions of the maximum output eg, ¼ power or 1/16th power.
To fill or not to fill?
Fill Flash: Fill flash is a technique in which you use your flash to essentially fill in areas of the scene, either because they are darker than surrounding areas or to intentionally darken the background to better illuminate a nearer subject. This technique can be used during daylight or in well-lit situations, even if the ambient exposure is appropriate, but where there is a big difference between the exposure values of the foreground and background (i.e. backlit or silhouetted subjects).
Flash Compensation: The control “Flash Compensation” affects the TTL flash exposure. TTL determines the out-put, but is not always spot-on. Simply look at the image, decide whether you would like less or more light and adjust the Flash compensation accordingly, by dialing in a + or – value. Thank goodness for the digital era…
Sync or sink…
(or at least that’s how I felt the first time I used a flash)
Flash Sync Speed: The camera has a maximum shutter sync speed for flash (around 1/200 second for most DSLR’s). The shutter must be fully open when the flash fires, to expose the entire area of the photo frame in that instant. At faster shutter speeds, the shutter curtains are never fully open all at once, it is only a narrow open slit moving across the frame. This means faster shutter speeds cannot be used for flash, or else we would get a dark unexposed band in our picture, where the total frame area was not open. The fastest shutter speed when the shutter is completely open to allow flash to go through it, is the definition of “the maximum shutter sync speed”.
Flash Fall-off: (Please note, this one relates to the Inverse Square law, but I am deliberately simplifying – no need to over complicate at this stage) Light intensity falls off rapidly over distance travelled. It is an easy concept… when the light leaves the flash it spreads out as it travels and becomes dimmer the further it goes. It loses intensity exponentially…for example, if the light has traveled a certain distance it might have lost 1/4 of its brightness. Travelling twice that distance it has not lost ½ its brightness as it is now only ¼ of its initial brightness. Don’t worry, just know light falls off fast over distance and therefor it is important how far the flash is from the subject.
Flash Exposure 101 to follow.
All Photo Credits – Sarel van Staden (Photowise)