A Guide to Flash Photography – Portrait Shooting

A Guide to Flash Photography – Portrait Shooting

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A Guide to Flash Photography – Portrait Shooting

As we get more experienced in photography, most of us would start to look for an external flash in order to create more versatile imaging effects and expressions. Have you ever thought of how many different types of shooting can a flash do? This article will talk about the usage of flash and the common lighting setups.

Flash Operation - M Mode

There are many flash modes to choose from, for example E-TTL Mode that controls the output based on the camera’s metering system and Ext. Mode that controls the output based on the external metering sensor. The flash mode we will discuss here is M Mode (Manual Mode).

Simply put, M Mode refers to manual adjustment of the flash’s output setting. Compared to other Auto modes, the manually controlled M Mode will not be affected by the ambient brightness and consistent output can be assured. If the shooting setup is within a considerably small area, for example when taking still portraits, M Mode is the convenient option to use and the resulting photos will look more consistent.

After setting the flash to M Mode, the major settings to adjust are the output power and focal length. To increase the flash’s output, we can either increase the output power or use a longer flash focal length for more focused flash light coverage.
Adjusting the output power: Take Speedlite 600EX-RT as an example. Press the second white button from the left and turn the dial to set the output power. We can set the output power from 1/1 (the highest) to 1/128 (the lowest) (as indicated within the red boxes)
Adjusting the focal length: Take Speedlite 600EX-RT as an example. Press the first white button from the left and turn the dial to set the focal length. The adjustable flash coverage is from 20-200mm (as indicated within the red boxes)
Apart from adjusting the output power, we can use a higher camera’s ISO setting or a larger aperture to increase the flash exposure. But be reminded that a longer shutter speed will not bring in more flash light as flash is an instantaneous light source.

Ambient Light vs Flash Light

Top left: Insufficient ambient exposure and without flash
Top right: Normal ambient exposure and without flash
Bottom left: Insufficient ambient exposure and with flash
Bottom right: Normal ambient exposure and with flash
When a flash is used, there are two light sources in the scene, namely the ambient light and flash light. The ambient light will affect both exposures for the subject and background – which is similar to how we shoot without a flash. Under normal circumstances, the flash light can only illuminate the subject but not the background in the distance, so we can assume that the flash light will only affect the subject’s exposure but not the background’s.

As we can set the ambient exposure and flash exposure separately, we can control the brightness ratio of the subject to the background for more versatile effects. For example, to outstand the subject, we can make the subject look brighter than the background. If we want to emphasize the background, we can set the same brightness level for the subject and background.

*The demonstration photos below were taken with an off-camera flash for more directional lighting effect. We can use flash triggers such as ST-E3-RT transmitter for wireless connection of the flash to the camera. Illuminate the subject from the side to create a stronger sense of depth.
Left: Normal ambient exposure and without flash
Right: Normal ambient exposure and with flash
To create balanced brightness for the subject and background, we can first imagine how we shoot without flash. Switch the camera to M mode and set the aperture, shutter speed and ISO like how we do in normal shooting to achieve an accurate ambient brightness. Take the above photo as an example. As it is our wish to retain the colors of the sunset sky, we should first do the metering based on the sky colors. For the above photo, ISO 100, f/11 and 1/30s were used.

Then we think about the flash part. Adjust the output power (1/2 for the above photo) until the subject is optimally lit. By handling the ambient and flash exposure separately, we can create photo with the subject and background equally and optimally exposed.
Left: Insufficient ambient exposure and without flash
Right: Insufficient ambient exposure and with flash
On the contrary, if we want a dimmer background to make the subject stand out, we should adjust the shutter speed and ISO setting so that the ambience is under-exposed. For the above photo, ISO 100, f/11 and 1/200s were used and the camera showed that the exposure was 2 stops below normal. So the photo looks dark. Then we add a flash to the scene. Adjust the output power until the subject is optimally lit (1/2 for the above photo). The final photo result shows a bright subject on a dim background.

After we thoroughly understand the relationship between ambient light and flash light, in addition to M Mode, we can also set the camera to Av Mode and flash to E-TTL Mode based on the shooting situations to help achieve accurate exposures for the background and subject in a quicker way. In the next article, we will look at the little tricks with the use of a lamp to achieve different lighting effects.
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