Creating better pictures: Speedlights

Exquisite Speedlight Usage

The previous issue's focus on speedlights detailed the relationship between light reach and film speed, and the difference between pictures taken with and without a speedlight. Let's review:

Terms describing Speedlight power (light output)

Guide Number (GN) = Aperture value X shooting distance * ISO 100 standard
[Example]
Up to how far from a subject could a GN 36 speedlight be in order for it to illuminate a subject sufficiently?
GN 36 = f/4 X 9m (light's reach) (116 = f/4 X 29 ft (light's reach))

How about a GN 14 speedlight?
14 = f/4 x about 3m (light's reach)
(44 = f/4 x 11 ft (light's reach))

Relationship between film speed and GN
GN measurement in catalogs and user manuals applies to ISO 100 film speed. Using higher-speed film such as ISO 400 film has an effect similar to using a high-GN speedlight. The higher the film speed, the more sensitive film is to light, so you can increase flash shooting distance by using a high speed film.

New GN = GN x (ISO/100)
[Example]
Using a GN 14 speedlight with ISO 400 film, new GN = 14 x

(400/100) = 28, for the same effect as using a GN 28 speedlight with ISO 100 film.

So much for what was covered previously.

This issue introduces effective techniques when using a speedlight.

Slow synchronization
You might have used a speedlight to take a picture with a beautiful background only to have the subject (but not the background) appear in the photo.

This happens because when a speedlight is turned ON, it automatically sets the shutter speed within the range from 1/30 to 1/250 sec., leaving the background underexposed.

If your camera has a slow sync (synchronization) mode, use it to slow down shutter speed automatically. This exposes background beautifully.

Single Lens Reflex cameras without slow sync mode can also take slow sync pictures.
	1. Set the exposure mode of your camera to "M (Manual)". 2. Set the aperture value of the lens. 3. Set the shutter speed for adequate background exposure. 4. Set the speedlight to TTL mode. 5. Turn the speedlight switch ON. 6. Check the light's reach with the LCD indicator. If you do not have an LCD indicator, figure out the shooting distance using the aforementioned GN equation. 7. When the speedlight has finished charging, take the picture. 8. Slow sync requires slow shutter speed, so try using a tripod. The subject should not move after the speedlight flashes until the shutter is closed.
Daylight fill-in flash Speedlights are useful for more than just indoor or nighttime shooting. When taking a picture with the sun behind your subject, the subject's face appears dark in the exposure. If you boost plus (+) exposure compensation, the background will be washed out, and the subject will not be contrasted clearly against the background. In such cases, use of a speedlight provides better balance of subject-to-background contrast. As occurs with slow sync, shutter speed will become fixed when the speedlight is switched ON.The balance of exposure between main subject and background is determined by the aperture. Therefore, make sure to set exposure mode to "A (Aperture-priority auto)" or "M (Manual)" mode, rather than "P (Programmed exposure)" mode. Camera technology not only makes cameras automatic; it also makes speedlights automatic. Experiment by taking pictures with backlighting, and achieve effects like you've never seen before in your photographs.


taken with a speedlight f/111/30 sec.	taken with slow sync mode f/111 sec.


without exposure compensation	with plus (+) compensation	shot using speedlight