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Tips & Tutorials >> All Tips & Tutorials

What are the Benefits of an External Flash?

Wondering if you should make that investment in an external flash? This article explains the benefits an external flash has over a built-in flash. (Reported by: Masakatsu Nagayama)

Speedlite wedding portrait


FAQ #1: My camera has a built-in flash. How is an external flash different?

A1: An external flash is more powerful for casting light into a far distance, or ensuring sufficient coverage when shooting with an ultra-wide angle length.

The built-in flash (also called a pop-up flash) that comes with most cameras, including DSLRs and mirrorless cameras, is indeed very convenient to use. However, it also has a number of limitations, which can be overcome by using an external flash.


1. Flash-to-subject distance

Flash-to-subject distance refers to the maximum distance that the subject can be from the flash to ensure that it is illuminated. The light from the flash is unable to reach subjects that are located beyond this distance, and the image will turn out underexposed as a result.

Built-in flashes generally have a maximum flash-to-subject distance that is limited to 1 to 3 metres at ISO 100.

External flashes have a higher flash power than built-in ones, with some capable of illuminating subjects that are located more than 10 metres away. In other words, you can use them to ensure sufficient lighting on subjects that are located further away from the camera.


2. Angle of coverage

The angle of coverage, also known as the flash angle, refers to the area that the light from a flash can cover in terms of the lens angle-of-view (focal length).

Built-in flashes have an angle of coverage designed to cover an angle-of-view equivalent to the wide-end of a standard zoom lens. This means that if you are using any focal length that produces an angle-of-view wider than the angle of coverage of the flash (for example, a wide-angle lens), the edges of your image might still appear dark. If you are using a lens with a long body, you might also get the dreaded “lens shadow”, where the shadow of the lens is captured in the image.

External flashes, on the other hand, can cover a wider flash angle. This means that they can brighten the entire image regardless of the type of lens used—even if you are using a wide-angle lens.


3. Direction of light

Built-in-flashes can light a subject only from one direction—the front. This could be sufficient for some scenes, but in others, such as in portrait photography, the front lighting from head-on could make the subject appear flat.

Meanwhile, many external flashes, including Canon’s Speedlites, feature flash heads that can be rotated or tilted to achieve different lighting directions and angles. Canon’s Speedlites can also be operated off-camera for even more flexibility in lighting direction (See FAQ #2).


Built-In flash

Although a built-in flash does not need to be carried around separately, it also has disadvantages such as insufficient flash power and ability to cast light only in the front direction. To produce more professional results, the use of an external flash is recommended.


external flash

An external flash unit that can be attached to the hot shoe(see FAQ #3) is also known as a “clip-on flash”.


FAQ #2: Besides more power, what other advantages does an external flash have?

A2: It has other features that provide you with more freedom to capture photo opportunities and create effects not possible with a built-in flash.

Besides the advantages mentioned in FAQ #1, an external flash also has other advantages:


1. A shorter flash recycle time

An external flash has its own power source, which enables it to recycle faster. In other words, the recovery time is short from the point the flash is fired until it is ready for the next flash, which means the photographer is less likely to miss out on a photo opportunity.


2. More creative possibilities

If your external flash has an adjustable flash head, you can tilt and change the angle to carry out bounce flash, which results in softer lighting that is less harsh. If the external flash supports features such as wireless firing and linking with multiple flash units, you can achieve effects that are even more sophisticated.


Built-in Flash

Flat lighting with built-in flash

EOS 70D/ EF24-70mm f/4L IS USM/ FL: 70.0mm (112mm equivalent)/ Manual exposure (f/4.0, 1/50 sec, EV±0)/ ISO 320/ WB: Manual
Light from the built-in flash illuminates the subject head-on but does not reach the rest of the image. This results in unnatural lighting that can make the subject appear flat. 

External Flash

Indoor portrait that looks more natural, using an external flash

EOS 70D/ EF24-70mm f/4L IS USM/ FL: 70.0mm (112mm equivalent)/ Manual exposure (f/4.0, 1/50 sec EV±0)/ ISO 320/ WB: Manual
 The settings such as aperture, shutter speed and ISO speed remain the same as those in the built-in flash example, but the external flash is powerful enough to reach further behind the subject, resulting in lighting that looks more even and natural. Wireless firing was used to light the subject from the left of the image, giving the subject more dimension. 


FAQ #3: Can I use an external flash on any digital camera model?

A3: You can mount an external flash on any DSLR camera.

Canon’s DSLR and mirrorless cameras (excluding EOS M100 and EOS M10) are equipped with a hot shoe at the top of the body for attaching an external flash. Before doing so, however, it is important to check whether the external flash is fully compatible with the camera you are using as there are cameras that do not support some of the features on the flash unit. For Canon’s compact digital cameras, the high-end ones that come with a hot shoe also support flash photography using an external flash unit.


Hot shoe

Among the different types of accessory shoes located at the top of the camera body, those with sync contacts for transmitting electrical signals are called a “hot shoe”.


Hot shoe

PowerShot G1 X Mark III, the flagship model of the PowerShot G series, is equipped with a hot shoe that allows an external flash to be attached.

Check out our series of articles on what to consider when you buy an external flash, coming soon. 


To learn more about how to choose from different Canon external flashes, check out:
Which Canon Speedlite Flash to Choose?

To learn more about individual Speedlites, go to the following articles:
Buyer's Quick Guide: Speedlite 270EX II
Buyer's Quick Guide: Speedlite 430EX III-RT
Buyer's Quick Guide: Speedlite 600EX II-RT


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Digital Camera Magazine

Digital Camera Magazine

A monthly magazine that believes that enjoyment of photography will increase the more one learns about camera functions. It delivers news on the latest cameras and features and regularly introduces various photography techniques.
Published by Impress Corporation

Masakatsu Nagayama

Masakatsu Nagayama

Runs an advertising studio, and started being a freelance photographer in 1998, where he has been active mainly in the advertising scene, shooting for magazines and online media. His speciality lies in snapshots of city life.