What to look for when buying an external flash
So you've decided to buy an external flash, what are the features that you should be looking for?
Tilt & swivel capabilities:
Most external flash units today allow the flash head some degree of freedom to be tilted and twisted in any direction. This is a very basic feature that people forget. Focusing your flash can significantly enhance your photographs. A flash head can be directed to focus on another surface and have the light diffuse on your subjects creating a well lit picture. Directing your flash on the subject creates what is called “harsh light".
Off-camera connecting socket:
One advantage that an external flash unit offers is the ability to direct your light from any angle and direction you want. So most of the time the flash unit is not directly on top of the camera, but rather off the camera and placed at a different locations and angles. In order to trigger the flash in such situations, a cable can be connected to the flash unit and when the shutter is released the flash goes off. This triggering mechanism requires a connection socket to be present both in the camera and the flash unit. There are alternatives to this (like the use of a remote controlled flash trigger), but it’s good to have the port of the flash for a quick direct connection.
Image Courtesy: Denniskatinas
For anybody who wants manage the overall results of their photos, manual control is an important feature. Let’s say you want to backlight your subject to get a white background, but also have the subject well lit; then the option would be have your flash unit fire at a higher intensity than the one in the front. This kind of fine control is made easy by presence of the manual controls on the flash unit.
Weatherproofing of the flash:
Granted that we take care of our photographic gear, we still try some creative shots in less than optimum weather! So as the camera, the flash unit needs to be weatherproof. Mostly all of Canon and Nikon flashes are well built and, with a little care, can be used in non-optimal weather. When looking at third party flashes one has to be careful of their weather proofness. There are sleeves that you can buy to safeguard your flash unit.
Silent operation capability:
This is mostly a personal preference, but I don't like external flash units that buzz and humm! A good flash unit is silent and smooth to operate and doesn't disturb the subject or draw their attention.