Manual flash exposures

To get a constant flash output, switch to Manual flash and set the power level yourself

With Manual flash, the scene isn’t automatically metered and measured in the same way as a TTL flash exposure. Instead, you tell the flash unit to fire a specific level of light regardless of what’s in the picture.

The flash power level can be adjusted in fractional increments – from 1/1 (full power) to 1/2 (half power, 1/4 (quarter power) and so on. You can typically go down to 1/128 power, although some high-end flashguns offer even finer control; the Canon Speedlite EL-1 can go as low as 1/8192 power, for example.

If you set a high power then you’ll get a brighter flash exposure. The drawback is that you’re unlikely to be able to rapid fire bursts of shots, as the flash unit will need longer to recycle between each flash.

As well as enabling you to add more subtle degrees of flash, lower-powered flash allows you to take a sequence of pictures in quick succession. The flashes are also shorter in duration, which means that you don’t get the motion blur that you sometimes see on moving subjects that have been shot with high-powered flash.

Grey matter … but it has overcompensated for the pale background to leave this shot looking grey. The Manual flash exposure gives a consistent result, regardless of the change in background.

Back in black Here, the camera has reduced the output of the TTL flash exposure to ensure that the flower isn’t overexposed against the dark background…