How to choose a detachable external camera flash

Updated: 2022-08-02

Pretending natural light is not easy when the lighting conditions require you to use the flash and you don’t want the viewer to recognize it. However, with a detachable external camera flash and a little effort, you can achieve this and the results can be surprisingly good.

Not all Flashes are created equal

It is fair to say at the outset that not every flash is a good flash. Probably the biggest difference you will find between built-in flashes and on-camera external flash units. The built-in pop-up flashes have one major disadvantage, which is the impossibility of directing the flash, but on the other hand, their presence in the camera is an opportunity for many beginner photographers to try working with flash and you can also use it to fire an external, detachable unit or a smaller, compact size flash speedlite that is even more comfortable.

Advantages of external flash Units

Main advantage is the possibility of directing the flash to our liking thanks to the positionable head. This also goes hand in hand with the significantly higher performance of external camera flashes. This is indicated by the Guide Number (GN) for internal flashes reaching about 13 GN, the detachable flashes start somewhere around GN 20 and end somewhere around GN 80 in the case of powerful professional external camera flashes. 

Disadvantages of external flash units

And what is the disadvantage of an onboard flash? Theoretically, there is none, from a purely practical point of view it is the weight, which translates into the weight of the whole kit with the camera and also the necessity to have at least two sets of extra batteries to use the flash.

Master Flash Vs Slave Flash

When do we call the detachable flash a “slave”? How do we use this “slave” or “accessory” camera flash to increase the light quality of your pictures?

Most new cameras have a built-in flash that is less powerful than other dedicated flash units. To get the most from your camera’s built-in flash, you can use it as a master unit to control other flash unit, the slave.

When an external slave flash unit is engaged it provides additional lighting for the camera when the built-in flash of the camera is activated, or any other flash for that matter. This little tool is especially helpful if you have a digital camera that does not have a hot shoe, but you want to add a more powerful flash to it.

The slave unit can be powered by the same batteries as the main flash unit, or it can have its own set of batteries. Some models have both an internal and an external battery pack. In most cases, the slave unit is small and lightweight and connects to the camera via a supplied cable.

With this technique, you can direct the slave flash unit where the main flash unit cannot reach. You can – for example – light up the shadow areas under a person’s nose or on his/her chin or if you are photographing a product shot and you want to include the background in your photograph, you can use a slave flash to add light to the background and even out the lighting.

When to shoot with a flash?

The answer to this question is very simple, whenever you need to get light into a scene and there is no other way to do it without the photo losing the intent. What are some of the most common reasons for a flash photography? Most often you can’t do without a flash in studio photography, wedding photography and you will also use it often in portrait photography or macro photography. When recording sports, the flash will be a useful tool (especially in the halls) and of course also social and documentary photography.

Camera flash for beginners tutorial. Using external light in flash fotography.

In each of the photo genres mentioned above, proper lighting will play a slightly different role, and most of the time they need to use it will force you to use specific exposures – for example, a higher aperture in low light to increase the depth of field that cannot be achieved in any other way. We will talk about aperture, exposure, and shutter speeds later in a separate article.

When not to shoot with a flash?

The flash is your friend but there are some situations when the usage of flash can result in poor digital photos. For example, when the object is too close to or too far from the digital camera the flash is practically useless. In certain situations, the flash can create unwanted shadows in the photo. A common fact is that flashes sometimes cause the exaggeration of details – e.g. when shooting a digital photo of an older person the skin wrinkles and imperfections details can be overly detailed.

When using the flash it is good to know its effective range.

Camera flash range. What is the effective range to shoot with a flash?

Digital camera’s flash units have a certain effective range. This is a limitation of how much light energy the flash unit can emit. Internal flash units usually have a shorter range than external, detachable flash units. If the object in the photo is outside of the flash range – the flash will not be effective and the object will be dark.

On the other hand, if the object is too close to the flash unit or the flash unit emits too much energy the object will be washed out. If your object is outside of your flash unit effective range you should turn off the flash and use slow shutter photography preferably with a tripod or another stabilizing mechanism.

If your flash unit allows the setting of the light power that will be fired (usually by setting the distance to the object) – make sure that it is set right to prevent washed-out objects.

In some scenarios, there will be enough ambient light to take a digital photo but without the usage of the flash, the digital photo quality will be very poor. In such a scenario, if the camera is left on the automatic flash mode it will not fire the flash. For example daytime photography with an object that is shadowed. If the object is wearing a hat it can create shades on the object’s face or when the object is lit from the side the object’s nose can create shades too.

Putting the flash in manual fill-in mode will force the flash to fire. The flash will lit those shadowed areas and prevent the shades in the final digital photo. The object of course must be in effective flash range.

Another example is an object that is lit from behind such as when taking a digital photo of an object against a sunset. Without a fill-in flash, the photo will likely be just a dark silhouette of the object.

Recycle time

Recycle time of a camera flash refers to the time needed for a flash bulb to recharge after emitting light. It is measured in fractions of a second and is one of the factors that determines the speed of a flash. A fast flash bulb has a short recycle time while a slow one has a long recycling time.

The flash bulbs for cameras used by most of the professional photographers are almost always “super” or “high performance” types. These bulbs have very high peak power (typically around 2,000 watts) and very short recycle times (typically 1/100th of a second).

Flash duration

The flash duration is the amount of time the flash emits light.

It is measured in fractions of a second, from 1/100 of a second (1/100s) to 1/10,000 of a second (1/10,000s). The lower numbers are used for “naked-eye” exposures and the higher numbers are used for precision work.

Most people use somewhere in the middle… 1/250 of a second to 1/8000 of a second.

What is the best type of detachable camera flash to use when taking photos of people? (incandescent, fluorescent, LED, etc.)

Generally, you want to use a flash that is as close in color temperature as possible to the light in the room or the environment. If you are taking pictures at an indoor party, then you need to use a flash that can match the existing tungsten light.

If you are taking pictures outside on a bright sunny day, then you should use a flash with a color temperature similar to the sunlight (around 5500K). If you are taking pictures inside a building or some other type of controlled lighting situation, then you can use any type of flash you want. However, in this case, it is important to know how to properly use the various types of available flashes so they will work to your advantage and not be a disadvantage.

What is an incandescent flash?

Incandescents were the most common type of a flashlight used by professional photographers a decade ago. In an incandescent bulb, the light is produced by heating a metallic filament until it becomes able to emit light into the environment. 

Incandescent camera flashes are not as efficient as other types of flashes. To capture an image with a flash, most of the energy in the flash has to be converted into visible light. Any energy not used in this conversion is wasted as heat, and incandescent camera flashes generate an awful lot of heat!

Another type of detachable flash lights are the flashes that use fluorescent bulbs.

What is the fluorescent (CFL) flash?

External CFL flashes are typically made of a clear or white bulb, with a small amount of mercury inside. When you give the bulb a quick burst of electricity, the mercury vapor inside will glow, producing short-wave ultraviolet radiation. This is the same kind of UV light that causes sunburn. There is a fluorescent phosphor coating on the inside of the bulb and the emitted ultraviolet light triggers the phosphor to emit visible light.

By using CFLs over traditional bulbs, a large amount of electricity is saved. This result is a reduction in greenhouse gas emissions (including mercury) from power plants due to the fact that CFLs use less power and consume less power. Each CFL bulb contains an average of four milligrams of mercury – a very small amount compared to the older types of bulbs.

What is the LED camera flash and how is it different from fluorescent and incandescent lights?

The LED (light-emitting diode) is a solid-state, artificial light source that is about 1,000 times more efficient at converting electrical energy to light energy than a standard incandescent bulb. This means the LED produces far less heat than an incandescent bulb and therefore requires much less energy to operate.

Decreased energy consumptions also results in improved, quick recycling time.

The first generation of LED flashlights were expensive and had a short life span. However, because of technological improvements, today’s high-quality, small, reliable LEDs are very affordable and last much longer than their predecessors, regular incandescent or fluorescent lightbulbs.

And since it does not contain mercury, it is also much safer for the environment. Today, LEDs are used in everything from large-scale lighting applications such as street lights and parking lot lighting, to much smaller scale uses such as the flash on a digital camera.

Continuous lighting vs a Flash

The alternative, of course, is the continuous light source, which today is already at a very high level, and you can buy an LED panel of very compact dimensions with the ability to change not only the intensity of the light but also the color temperature, and all this still powered by a 2000mah li-ion battery or even standard AA batteries (think green and opt in for rechargeable battery models). 

Continuous lighting

600W Day Light Umbrella Continuous Lighting Kit by LimoStudio

However, constant lighting is the domain of video recording in particular, where constant bright light source makes much more sense. In the case of photography, perhaps only a powerful reflector aimed at the ceiling can be used to create ambient lighting.

By reflection or through a diffuser?

Although an external camera flash unit will offer more output, this does not mean that its light should blind the subjects. The higher flash power is available here to create sufficient ambient, natural light of the scene for a short moment.

Turning the flash towards the ceiling, from which the light bounces and diffuses, results in a soft level of brightness without harsh shadows that is much more pleasant and natural both in intensity and in its top-down direction, much like the sun shining down. The ability to turn the reflector and bounce the light off the ceiling or wall will help to make the photos look more natural, without harsh shadows.

With diffusers

SMALLRIG Rectangular Softbox with Quick Release Pressing Design, 60 x 90cm (23.6″ x 35.4″)

If you find yourself in a situation where it’s not possible to shoot with the reflection against the ceiling, there is no choice but to point the flash towards the subjects, but always with the addition of a small diffuser or larger softbox. This is because it allows us to achieve diffused light that is much more natural lighting, especially when we don’t overdo it with the flash output.

A diffuser for an external camera flash is usually included in the accessories. If you need a wide-angle diffuser, this is not part of the set but you can buy them cheap online (wide angle diffusers are used for example in real estate photography and by the event photographers as they spread the light in wider angle). A less used but practical solution is also the combination of flash and diffuser plate, where usually the flash is placed outside the camera and the diffuser plate then directs its light where it is needed. In the case of outdoor photography, the reflective plate can even replace the flash itself in some situations.

What about the universal Camera flashes for every brand?

Although less common, you may still come across universal flashes that have only one center contact, which is used to fire the flash regardless of the brand of camera. When working with such a flash, you need to be in constant control of its settings and project your own camera settings onto it, which can often be quite tedious. The disadvantages of such a flash are the need for full manual flash mode and the fixed and relatively long sync time of around 1/200 s.

TTL (through the lens) flashes

A more efficient way is a TTL flash, which is selected according to the camera brand and features multiple contacts on the hot shoe, so it is able to communicate with the camera and adjust its settings to the exposure values just selected.

TTL flash uses a series or infrared flash bursts to determine the distance to your subject and then adjusts the power of its output accordingly.

This is one of the most accurate ways to take a flash photo and it produces much more even lighting than either manual or auto exposure. It’s perfect for taking pictures of people because it will adjust the power output of the flash to make sure the person being photographed is not underexposed (too dark) and not overexposed (too light). 

The flash adapts to the selected focal length in the same way, if it has a zoom head I definitely recommend choosing one of these flash models.

What is the meaning of E-TTL and I-TTL?

At the present time, there are several variations of TTL flashes available on the market. There are three main types of external flash units you will encounter most often, which are E-TTL, I-TTL and P-TTL.

All three are pre-flash based evaluative flash metering systems.

E-TTL stands for Evaluative “Through the Lens”, i-TTL stands for Intelligent “Through the Lens”, P-TTL stands for Predictive “Through the Lens”.

What they do is, they measure the light that reaches the sensor after the flash has fired. Then they compare this reading with a reading they have recorded for the scene just before the flash was fired. If there is a significant difference, the flash system will fire again to bring back the readings to as close to equality as possible.

Canon ‘s E-TTL, Evaluative “Through the Lens” off-camera flash units

In order to determine the correct exposure of the flash, a low power preflash is fired immediately before the shutter opens and its reflectance is measured.  

The camera then uses evaluative exposure meter that measures the brightness of the entire image area that is being exposed. The exposure is adjusted up or down by 0.5EV increments depending on whether the brightness of the exposed frame is above or below the average brightness of the frame.

Again, this averaging is done on a frame-by-frame basis and entire image area is analyzed for exposure. This averaging feature is a very sophisticated one that allows for much more accurate exposure control than would otherwise be possible. In fact, this averaging feature is so effective, it is possible to get correct exposure in situations where neither ambient light nor active AF point alone would produce correct exposure.

For example, let’s say you are taking a picture of a person standing in front of a window. The window is 10 feet away and the light outside is fairly strong, say 10EV. The light inside your subject’s face may be only 3EV or 4EV (the exact EV value varies with individual faces), but because of the averaging feature of the metering system, the average brightness of the entire frame exposed by the flash is 10EV.

Nikon’s I-TTL, Intelligent “Through the Lens” falsh units

With i-TTL, a preflash from the flash is measured using a viewfinder RGB meter before the mirror is raised. With preflash, the lens is wide open, and the power flash power level is calculated according to the aperture. There is no further monitoring or attention (unlike film TTL which utilizes quenching).

Multiple flashes can be controlled via Commander, which can control groups of remote flashes. The ITTL can measure each flash individually (as long as there is only one flash in each group), and it can set individual power levels accordingly. 

Pentax P-TTL, Predictive TTL off-camera flash

P-TTL is a predictive flash metering system, whereas TTL is reactive.

With P-TTL, when the camera detects your subject is well exposed, it stops firing the flash. This allows the ambient light to fully come into focus, while keeping the shutter open for as long as possible to allow all of the subject to be recorded on the sensor.

The end result is much sharper, more detailed photos that are not underexposed or overexposed. And because there is no need for a long exposure, there is less chance of blurring from camera movement.

High Power Off-Camera Units

When the light is very low or you need to shine against really harsh sunlight, a high power output flash (e.g. GN 80) will come in handy, so it can easily serve as an alternative to studio flashes.

Which parameter should you choose according to?

Clearly by performance, where the higher means the better. In general, a guide number between GN 55 and 60 can be recommended if you intend to shoot in direct sunlight. Lower light output is more suitable for indoors or to lighten the scene for product photography.

The second most important parameter is the zoom range of the flash head, which is usually between 24 and 105 mm, which is usually sufficient, but if you would like to shoot with longer focal lengths around 200 mm, the flash selection should be adjusted accordingly.

Last but not least, it will also depend on how you want to trigger the flash unless it’s mounted in a hot shoe on a digital – on some cameras, this is possible using the remote flash control. Another option is to fire it using an internal flash whose flash is detected by the optical sensor of the detachable external camera flash – the downside is that the latter has to “see” the flash of the internal flash.

By far the best and most versatile solution is to use a standalone wireless launcher, which is very reliable even over longer distances, it works as a remote control and allows you to control the high-speed sync of multiple external camera flashes simultaneously if required. In terms of brand, we definitely recommend sticking with the same manufacturer as your camera.

Is an inbuilt camera flash really useless?

Definitely not, you just need to know how to use it. Even though it’s small, low power and its light is very close to the lens, plus on its axis, you can definitely use it. 

It is very common to use it when you are shooting, for example, a portrait in a backlight and you need to illuminate the subject’s face. In this case, an internal flash will suffice, but you need to reduce the power and ideally use a diffuser.

This can either be a small, snap-on flash, or you can actually use any material that diffuses and softens the emitted light like baking paper or non-woven fabric. However, in these cases, you should expect a higher light absorption and therefore you will need need to increase the power.