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An Intro to Flashgun Settings and Modes

An Intro to Flashgun Settings and Modes

Written by William Algar-Chuklin

Flashguns are small, lightweight, and powerful flash units used to light your subjects in various conditions. They’re really great, but it can be hard figuring out what makes one better than another.

The Rundown:

  • Guide numbers to guide you.
  • Flashguns can zoom too!
  • Common modes for your shoot.

What are Guide Numbers?

When looking at the power of a flashgun, the guide number advertised is the main way to express the power (i.e. the amount of light it can output) as a number. It’s calculated at a given f-stop multiplied by the max distance in meters from the subject, that allows the subject to be illuminated for an exposure at ISO 100 at the advertised focal length. Basically, if you wanted to shoot at ISO 100, the Gudie Number will give you a good idea of how far the subject can be from the camera while still being exposed.

The general rule of thumb is, the higher the number the more light it can output. Though be aware that some unscrupulous manufacturers will use ISO 200 instead to boost their guide number, so it’s good to see how they’re calculating it.

Zoom Setting

Flashguns also generally have a feature that allows you to zoom the flash head to match your lens focal length. This is what allows a flashgun to project light further away by narrowing the beam to increase its intensity.

This is a setting in the flashgun menu, and will help you get the best light output you can for the focal length you’re shooting at. You’re going to want to check this setting regularly if you’re shooting in manual mode, but when shooting in an automatic mode, most modern flashguns will actually read that setting directly from your camera and transfer that info to the flashgun.

Flash Modes

Flashguns come with a variety of modes and each can be quite useful in different situations. Let’s cover the most common ones:


This mode allows the flash to control the light intensity (i.e. power) of the flashgun automatically using an inbuilt light meter. It does this by firing off a preflash to measure the light needed before firing a correctly exposed flash to light your subject. The performance of this can vary, but good quality flashguns can perform well using this setting.


Through The Lens (TTL) metering is an improved auto mode, and allows for the exposure to be metered through the camera instead of a light meter in the flashgun. This can lead to more accurate exposure of a subject. Event and wedding photographers favour this setting due to the constantly changing conditions they need to light for. Modern TTL generally works very well, but can vary in consistency and accuracy based on the individual manufacturers TTL system.


This mode is used quite often for photographers who have absolute control over their lighting and shooting conditions. Think studio photographers. They’ve got the time to be able to dial in the exposure accurately. Manual mode allows for fine control over lighting and consistent and intentional light on a subject. It’s a really good idea to play around with the power output (expressed at a fraction, e.g. 1/1 = full power, ⅛ = an eight of max power, etc) on your flashgun yourself to get a better idea of the results. Lighting in manual mode is a powerful skill to have!

Master and Slave Modes

This mode allows for a flash attached to your camera to control the firing of other flashguns set to slave mode. This is done by having the master flash fire off a preflash that triggers the others in the group. This can be extremely useful in a pinch to control creative multi-light setups. There’s also the option to use radio triggers instead which can allow for full TTL features for the slave flashes.

Other Features

Swivel Heads

Fully featured flashguns will also have the ability to adjust the flash head direction whilst mounted on a camera. This is useful for using ceiling and walls as massive bounce cards. As a rule of thumb, the larger the light source the softer and more pleasing the light. It can be extremely useful for a flashgun to be able to use a white ceiling or wall to increase the size of a light.

Bounce Card

These are tiny cards built into the flashgun that can be pulled out. They can be useful for providing some additional directional fill light and are generally used in conjunction with bounce lighting to also provide highlights in eyes.

Wide Angle Diffuser

This is a pull out translucent cover for the flashgun head. It helps diffuse light in a larger angle for situations where you’re shooting at a wide angle. It’s good to keep in mind that this can cut the light output of the flashgun by at least a stop, and will need to be compensated for.

Signing Off

This covers the main features of a flashgun. Flashguns are a powerful tool and add to the useful skills a photographer can have. Hopefully this intro into the basics of flashguns helps you choose the right product for you. I recommend getting the most powerful flashgun you can get. The extra versatility, and the problem solving they can provide are well worth the expense!

If you need more information, check out some of our other articles on the C.R. Kennedy blog.

William Algar-Chuklin is a night and travel photographer based in Sydney, Australia. You can check out some of his work at walgarch.com and on Flickr