Flash Photography Tips
Part 3: TTL Flash Photography special features
In previous articles I discussed the differences between constant light vs. flash photography and also some tips about TTL Flash Photography. In this article I am going to cover some important features of TTL flashes. Often photographers have asked me why TTL flashes are so expensive compared to non TTL flashes. The reason often comes down to convenience; below is a list of some of these conveniences.
1- Camera controls the output of the flash, so you have peace of mind that you always get correct exposure.
2- When you mount your TTL flash, your camera automatically sets the correct White Balance for Flash Photography, so you don’t need to worry about colour shift. Many of the new Nikon flashes (SB900, SB910, SB 710) come with colour correction filters; when you use these filters, the camera recognizes the colour filters and adjusts the White Balance accordingly.
3- Allows shooting using High Speed Synch (HSS).
What is High Speed Synch (HSS)?
High Speed Synch is one of the most useful features of TTL Flashes. High-speed synch flash is your DSLR’s ability to use a flash at shutter speeds faster than the camera’s native synch. Most cameras have a native synch of 1/200th of a second, and anything faster than that is beyond the camera’s ability to synch the shutter with the flash. But if you happen to be in a situation that requires faster shutter speeds to effectively capture the action, or for other aesthetic reasons (like a wide aperture), then you’ll over-exposure your image. However, high-speed synch flash/camera combinations allow you to use the flash at higher shutter speeds.
When are the times to use High Speed Synch?
High-speed synch flash is used when you want a shutter speed that is faster than your camera’s native flash synch speed, or when you want to use a wider aperture setting that requires a higher shutter speed as is often the case with outdoor daylight shooting. For example, you want to take an outdoor portrait and your TTL meter tells you that the f-stop should be f/16 with a 1/125s shutter. Those settings will give you too much depth of field, way too much actually. Nearly everything in sight will be in focus. Instead, what you want is a sharp subject, but a soft, blurred background, which would be achieved with an aperture of about f/2. That’s six stops of light difference, effectively putting your shutter speed up to 1/5000s. This is easily achievable by setting the flash to High Speed Synch. When you take your photo, you’ll have that beautiful, soft background that the pros get when shooting outside. You’ll also want to use HSS when you’re shooting with a telephoto lens, trying to capture fast action, using a fast shutter speed as well as a high f-stop. So in sports photography High Shutter Synch is ideal, and in some wildlife situations as well.
How does High Speed Synch work?
With a high-speed synch flash-capable camera and dedicated flash unit, all you do is set the camera to that setting. But how does it really work? Basically, at high shutter speeds the rear curtain starts to close before the front curtain fully opens. This way only a sliver of exposure moves across the image sensor. It is within this moving sliver of exposure that the flash fires, and voila! A high-speed shutter speed is synchronized to the flash. The flash does fire several times more during shutter traveling time than with standard flash mode. In standard flash mode, the flash fires once and the duration is much shorter than the time it takes for the shutter to move across the image sensor, and before the partially opened shutter covers part of the frame leaving large sections of black in your image. The underexposed black bands in the image is not good, to say the least!
Stay tuned for our next article about Manual Flash Photography. Meanwhile head on over to our Upcoming Classes page and check out our exciting lineup of upcoming workshops. As always, feel free to contact me if you have any questions.
Ted and Omnilargess Team