What you'll learn
1.How to set up a flash on manual
2.How manual flash and TTL differ
3.Why TTL can really fail you
TTL (Through The Lens) flash can be really useful, but for many types of photography, manual flash is crucial. This short tutorial will explain how manual flash and TTL differ and how to set manual flash up.
What you'll need
- Speedlight with manual settings
A bit of theory
Most modern flashes have at least two modes, TTL (this can be eTTL, iTTL etc) and manual. Both modes result in the flash illuminating the scene, but they differ significantly – both in use and in the way they do their job.
TTL stands for Through The Lens metering. This means that the amount of power the flash needs to put out is calculated automatically. This is done by the flash unit sending out a small pre-flash, and then the camera and flash calculating the correct amount of light that the flash needs to emit. One of the main advantages of using TTL is that you don’t need to think about changing the amount of power on the flash, so for shooting events or similar it can be super useful. The main time that TTL fails is when you want complete consistency between shots.
Switching the flash to manual allows you to take complete control of how much power comes out of the flash. Combined with using your camera on manual, you can create really consistent photographs. The settings on the flash are typically displayed as fractions of the full output, the most powerful setting being 1/1 (full power) and you can often change it the whole way down to 1/64 or 1/128 power. You should note, however, that at full power, the flash is working its hardest so it can take a while for the flash to recharge. Dropping the power down will help to decrease this time, but will also decrease the power.
The other key difference here is that the flash power will not adapt to the camera settings, so in order to correctly expose using manual flash, you have to think a little about your camera settings.
The first and most crucial thing to know is that changing your shutter speed will not change the flash exposure. Cameras also tend to have a maximum shutter speed that flash can be used with, known as the sync speed. The maximum sync speed tends to be around 1/125th. If you try and set the camera to a faster shutter speed then you run the chance of not catching the flash at all. The shutter speed will continue to change the ambient exposure, so if you want to introduce more ambient exposure, think about slowing the shutter speed down to longer than 1/125.
Aperture and ISO will both influence the flash exposure. Aperture will only influence the flash exposure, so adjusting your aperture to make the scene brighter or darker is your best bet. Changing the ISO will adjust both your flash AND your ambient exposure.