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|Category:||Studio Lighting and Flash|
Understanding Flashguns - Part 3 - Mark Elliott of Better Photos shares his advice on operating flashguns.
Flashguns typically have two main operating modes: Fully Manual and TTL.
Manual Flash ModeManual flash mode is useful when the distance between your subject and flashgun is fixed, or your subject travels through a pre-set position. It’s also a good setting to use to learn the basics about your flashgun. Light output is repeatable and is not influenced by the distribution of light in the camera frame.
The flashgun has a range of power settings from full power (1/1) to as little as (1/128) on the higher specification units. Power can usually be adjusted in 0.3 or 0.5 stop increments.
When using your flashgun in manual flash mode. YOU set the power level by hand. How do you decide what power level to set? You can do test shots, check your histogram, highlight alert warning or use a hand held flash meter. Too much light on your subject? Turn down the power. Not enough? Dial it up.
TTL ModeTTL mode automates your flashgun. The FLASHGUN sets its own power level. Clever eh? It does this by firing a pre-flash, which is used to calculate the brightness of the subject. With compatible lenses, it also throws into the mix camera to subject distance information. Camera and flashgun ‘talk’ to each other, communicating these details. Based on this, your flashgun adjusts flash power automatically and immediately triggers the ‘main’ flash that is used to expose your subject.
TTL mode lets the camera and flashgun do the work. It’s ideal for situations where the distance between the subject and flashgun constantly changes.
Sounds great, but what’s the downside? Because flash power is set automatically, it’s not possible to know the power settings it chooses, or why, making repeatability and consistently lit photographs sometimes tricky.
Flash Exposure Compensation (FEC)There are times when TTL mode gets it wrong, resulting in under or overexposed subjects. However, you do still have an opportunity to make adjustments to the flash power in TTL mode by using Flash Exposure Compensation (FEC). Usually within a range of -3 to +3 stops, in 0.3 (or 0.5) stop increments.
To use FEC, take your shot in TTL mode and then review your image, histogram and highlight warning alert. Dial in more or less FEC as required and take your next shots. Continue to adjust as necessary.
There are no difficulties triggering your flashgun when it’s mounted into your camera’s hotshoe. Press your camera’s shutter button and the flashgun is fired in the flash operating mode you’ve chosen (manual or TTL). It gets a bit more complicated when your flash isn’t mounted on your camera.
Triggering your Flashgun Off Camera
It’s important to point out that, when you take your flashgun off camera and want to use it in TTL mode, you need to use specific pieces of equipment that allow your camera and flashgun to communicate complex TTL information with each other. These devices tend to more expensive ‘solutions’ than those needed to trigger your flash in manual flash mode. A flashgun in manual mode simply needs to be told when to fire.
Different Flash Modes – Different Solutions
Triggering your Flashgun 'Off Camera' in Manual Mode
Methods of triggering your flash in manual mode don't need to transmit TTL information; they just need to say FIRE!
You can use any of the following to trigger your flashgun in manual mode:
- Sync Cords
- Infrared Triggers
- Manual Radio Triggers
- Optical Slaves
Triggering your flashgun in TTL mode requires complex TTL information to be transmitted between flashgun and camera, which the flashgun then uses to calculate its power output. Because of this these devices tend to be more expensive, and include:
- Built in wireless (Requires another compatible flashgun or ‘commander’ unit in your hotshoe mount)
- TTL Cord
- TTL Radio Triggers
Distance and Position IssuesWhen buying triggering devices, it’s important to consider the distance and position of your flashgun in relation to your camera. Triggering solutions, whether used for TTL or manual mode often operate within a limited range, and some devices must have line of sight between trigger and flash unit. To avoid disappointment, check these details before you buy the device.
Mark Elliott is a Cumbria based portrait and commercial photographer. He also runs Better Photos Photography Training.
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