Speedlights, Speedlites, Flashguns, Off-Camera Flash

A Guide To Using Speedlights AKA “Off-Camera Flash”

The off-camera flash is an important part of a photographer’s lighting gear. Depending on the brand you use, to Nikon it is called Speedlight while Canon uses the name Speedlite. They are both the same thing in functionality, but just differ in manufacturer specifications. This technique of using speedlights is also called flash photography. These are just marketing names for an off-camera flash unit also called a flashgun. For the purpose of this article, I will be coming from a Nikon perspective so I will use speedlight to refer to the off-camera flash unit.

It is a simple concept. You attach a light source to your camera to get more lighting and you can create better images in dark conditions. Using the speedlight is common for event photography, when the lighting is not consistent. Venues have locations that have good lighting in some areas, but most places do not have sufficient lighting for taking photos. It also doesn’t help that many events take place in the evening or at night when there is less ambient light available. This is where the speedlight comes in and saves the night.

The SB-900 Speedlight (Source Nikon USA)

Basic Operation

The speedlight in its most basic operation triggers an off-camera flash when the shutter button is released from the camera. It is attached to the hot shoe mount on a compatible DSLR or mirrorless camera. Don’t forget to lock it, because these units can easily fall off and get damaged. A typical speedlight requires 4 AA batteries at 1.5 V each (total of 6 V). The connection to the hot shoe creates an electrical path to the camera, which allows an electronic signal to travel from the camera when the shutter button is released in order to trigger the flash to fire.

Most digital cameras, including DSLR, have an on-camera flash, but it doesn’t produce as much light in some situations as a speedlight. The speedlight can also be adjusted to different angles to bounce or reflect light to the subject, providing more flexibility to photographers in how they place the light source. Another advantage of speedlights is it can be remotely triggered when connected to wireless triggers (e.g. Pocket Wizard), allowing the photographer to place the light source in different locations to illuminate the subject.

Speedlights can also be attached to brackets and mounting rigs. They can be either directly wired to the camera (e.g. using AGFA Off-camera shoe cord) using the hot shoe mount or they can be triggered wirelessly. This allows photographers to attach several speedlights and trigger them all at the same time by configuring a master speedlight unit. On-camera flash does not have this versatility available since it is built-in to the camera.

Exposure Modes

TTL or Through-The-Lens Mode is the first exposure or flash mode used with a speedlight. TTL automatically uses the camera’s built-in metering system (e.g. spot, center-weight, etc.) that measures the distance to the subject based on the focal point. This allows the speedlight to determine how much light to fire for the exposure. Since this is determined by the camera metering system, one must be aware of the other settings that can determine the light. This requires understanding the exposure level on camera (this is more for manual mode use), which is also called the exposure compensation (EV). This is found in the back of the camera (refer to your camera’s documentation) and can be adjusted by Positive (+) or Negative (-) measured in stops. When adjusting (+) you want more light, while (-) decreases the light.

Locating the Exposure Compensation on a Canon DSLR. These settings can be made on camera when shooting flash in manual mode. (Source Family Tech Zone)

When your exposure compensation is set to +2 EV, the TTL mode will add 2 stops more light to the image. If that is too much light, you can adjust it one stop down to -1 EV. There is no exact value, as the lighting in any location is always variable. It is up to the photographer to come up with best setting, but must take into account the environment. If the location is too dark, more light is needed (adjust Positive EV up). When there is sufficient lighting, but the photographer needs some fill light that won’t overexpose the image, less light is needed (adjust Negative EV down).

There is also a flash compensation which allows the photographer to control the exposure level from the flash unit. Certain speedlights allow the EV to be adjusted for the flash to be used by the TTL along with the camera’s metering system. Depending on the speedlight specifications, the flash compensation can be used to alter flash output from -3 EV to +3 EV in increments of x EV (x can be a value that is set by the manufacturer of the speedlight).

Flash compensation settings on the SB-600 speedlight (Source Nikon)

The other mode option a photographer has is Manual Mode. Since it is manual, the settings must be determined by the photographer. This includes the exposure compensation, distance to subject, focal length, GN and the amount of power output for the light. This is more of a trial and error for the photographer to determine the best exposure. This requires understanding the concept of distance to flash which is explained by the inverse square law. There is an actual science to this that is shown by the use of Guide Numbers (GN). One thing to remember about GN is the relationship of the distance of the flash unit from the subject. It shows that the brightness of a flash declines with the square of the distance while the amount of light admitted through an aperture decreases with the square of the f/stop. I explain GN in more detail on my article “Photography Lighting (Part 1) — Studio Portraits”. You do not need to memorize this, as these values are given by the manufacturer for specific speedlights.

These are GN values (in feet) at ISO 100 for given zoom setting focal length for a Nikon SB-600 speedlight. (Source Ken Rockwell Photography)

There are other exposure modes not discussed, but those are manufacturer specific. More information about those modes are available from the provided documentation.

Power Output

On Nikon speedlights, the photographer can determine the amount of power for the lighting when using Manual Mode. This is adjustable on the speedlight, like the SB-600, SB-800 and SB-900 units. The more illumination you need, the closer the value to 1. It can be measured in increments from 1/1, 1/2, 1/4, 1/8 … 1/64 (it doubles for every increment). Take for example a brightly, well lit room where you don’t need full light from your flash. You can either point the flash up toward the ceiling or from another angle. Better yet, you can reduce the amount of power that is a fraction of the maximum output level from the speedlight. You can adjust the power output level to 1/8 of full power, pulling less light from the flash. (More information can be found from the manufacturer’s documentation) This gives photographers more control over the lighting.

If your speedlight is rated at 60 W at full power, then its power output level is:

PO = Power Output = W x sec
60W x 1 sec = 60Wsec

For every second the speedlight is used, it has a power output of 60 W. If you use only 1/4 of the speedlights full power output, then it is:

1/4(60W) = 15W

These are not exact values, but approximations to give an idea. There are other factors that are involved in calculating the exact power output, including how much power batteries are providing to operate the speedlight.

In TTL mode, the speedlight will send a quick burst of light that measures what the power level should be. It doesn’t require the photographer to set it, it is done automatically. With TTL the speedlight knows when the subject is closer or farther from the light. Allowing the speedlight to determine the power level to light the exposure has its advantages when shooting at live events or random moments. The photographer has no idea about the distance to flash power level so it lets the speedlight figure it out using TTL.

Commander Mode

Some speedlights use what is called a Master Speedlight or Commander Mode which supports triggering multiple speedlights. This allows the photographer to configure a master flash unit by enabling commander mode. This is a feature available on the Nikon SB-900 speedlight unit. This allows multiple speedlights to trigger from the master flash unit. While all other speedlights are passive, the master unit which is active initiates the triggering of all the speedlights. If you are interested to learn how to configure an SB-900 to become a master flash unit, here is a comprehensive guide link on the DailyPhotography.net tips website.

Flash Sync Modes

There are different types of flash sync modes. They are used by the speedlight to determine when to trigger the flash with the camera’s shutter, which is referenced as a curtain. Front curtain sync means triggering the flash when the shutter opens. In rear curtain sync, the flash is triggered just as the shutter is about to close.

In the Nikon world, there are 5 types of flash sync modes.

1. Front Curtain Sync (Normal Sync) — In this mode the flash triggers as soon as the shutter opens. This is normally how a speedlight operates. The slowest shutter speed the camera uses is 1/60 of second and the fastest is 1/250 of second. This is also referred to as the flash shutter speed. Certain camera models allow photographers to change this in the “Custom Menu” settings.
2. Red-eye Sync with Front Curtain — There is a sync mode in the speedlight that helps to prevent the “red eye effect” in subjects. Red-eye is caused by the direct light from the flash hitting the subject’s eyes and reflecting off the back of the retina. The retina has a blood-rich red color, which the light from the flash illuminates. This can be avoided by bouncing the light at a different angle and not position the speedlight directly towards the subject. Another way is to use red-eye sync. In this mode, the camera will fire off a series of quick light pulse before the shutter opens. The light pulses help to constrict the eye pupils so that when the actual flash triggers it reduces the light that can enter the eyes, thus avoiding illuminating the retina.
3. Slow Sync — This mode allows the photographer to expose the subject while capturing the ambient light in the surroundings. The flash triggers at the beginning of the exposure using the front sync mode, but keeps the shutter open to gather as much ambient light as it can. This is actually a good sync technique for images that require the background to be in view with a smaller DoF (Depth-of-Field) or large aperture. This illuminates the subject along with the background and anything else within the frame. For tourists shooting in the poorly lit locations that require flash, this is an ideal sync mode to use. If the subject starts moving after the flash triggers, it can create motion blur since a slower shutter speed is used.
4. Slow + Red-eye Reduction Sync — This is mode 2 and 3 together.
5. Slow + Rear Curtain Sync — This is the same as mode 3, but uses the rear curtain sync. The flash is triggered at the moment the shutter is about to close, or the moment of the rear curtain in an exposure. When the exposure begins, the shutter opens to begin gathering ambient light. Then, when the exposure is about to end, the flash triggers. This mode is used for capturing the motion blur as an effect. Slow rear curtain sync can capture light trails and forward motion as blur during the start of the exposure. However, when the flash triggers it captures the subject towards the end of the exposure as a frozen still. In this technique it is recommended to lower the power output level of the speedlight so as not to overpower the ambient light.

Known Issues When Using Speedlights

I am sure every photographer has their own list of issues. It is an ongoing list, with new issues encountered with different types of speedlights. I am going to share a few that I have experienced when using them.

• Low Battery — What better way to ruin your photoshoots then with low battery on the speedlight. When you shoot at a high power output level, it can quickly drain the batteries. A bigger problem is low battery levels won’t allow you to continue and you will just need to change the batteries. It is also advisable never to mix old and new batteries together because they produce mixed results.
• Annoying — That is correct, it can be annoying. Not to the photographer who loves taking photos, but to the subjects. This is true when shooting events and public gatherings. Sometimes the photographer may shoot several times triggering the flash and that can irritate people. There are times an event organizer may ask the photographer to stop. Using flash photography for events is essential to capture the images, but there are times when it is not required. Photographers will need to either use a tripod or a low light lens, or shoot away from the crowd and move more closer to the subject.
• Not Damage Proof — They are expensive to replace when broken. Luckily I don’t just place speedlights anywhere. Accidents can happen so it is very important to take great care of them. Be aware of your surroundings at all times as well, because if you are not alert, someone could bump into your camera and speedlight.
• Hard To Shoot Bursts — Shooting in bursts depends on what is called the recycle time of a speedlight. If you want to shoot with the flash going off at 6 frames (exposures) per second, it will be difficult for it to trigger at each frame at that short of time. This is because the flash unit itself needs some time to recharge back to full power after triggering. This is called the Rated Recycle Time. A trick around this is to set the speedlight at a lower power output level (e.g. from 1/2 to 1/16) allowing less time to recharge between exposures.
• Overheating — Over time the speedlight can get hot due to use. If it overheats, the flash suddenly stops working and this can ruin the night for any event photographer. It will eventually start working again once it has cooled off, but there is no definite time on how long it will take. For those who really need to keep shooting with speedlights, having an extra one on hand is very useful.

Synopsis

A speedlight is something to add to a photographer’s gear. While I don’t cover techniques on using the speedlight, the basic operation and theory behind it were discussed. One final thing to remember is speedlights use light bulbs, just like strobes. The difference is that they are smaller versions from that used in studio lighting. It is hard to find an actual place where they sell bulbs for a speedlight, because there are so many different types. Some camera stores might sell them, but if the unit is really old they may not have it. The best thing to do is contact the manufacturer to order replacement parts or if the flash unit is really beat up, time to invest in a new one.