Understanding flash
Shelton Muller explains the techniques and technicalities that make flash photography easier and more creative.
Flash can be one of the worst forms of lighting a photographer can use. It’s cold, harsh and unnatural. On the other hand, when creatively used it’s the most desirable piece of portable sunlight a photographer could hope for – and therein lies the key. For flash to be of benefit to your photographs, it needs to be understood and creatively employed.
Flash can be used in many ways to enhance your images and make others possible. Far from being an accessory light source that you use only when “it’s too dark”, flash can be employed as a creative tool both indoors and out. In this article we’ll examine the technicalities of flash and its creative possibilities.
Guide numbers
While it’s not used so much these days, a flash’s guide number is still the best way to understand its output. The guide number of a flash is exactly that – a number to guide you in determining exposure. Once upon a time, this magic number was needed for photographers to accurately calculate their f-stops. While no longer needed for that purpose, it will still help you in your selection of flash and in understanding its reach.
The guide number is often included in the model number of a flash, but not always. For instance, the famous Metz 45 flashguns have a guide number of 45 in metres at 100 ISO. To determine the exposure the photographer could have made the following calculation, if his subject was four metres away: 45/4 = 11.25.
The correct f-stop for a full manual blast of flash was therefore about f11. By dividing the guide number by the distance in metres, the photographer calculates the correct f-stop. This would only apply, though, if he had 100 ISO film loaded. He would have to calculate differently, of course, if he was shooting faster or slower film. However, with the Metz 45 – as with most flashguns these days – the automatic features make life so much easier and seldom do we need to do this kind of maths. But it does give us an indication of the output of our flash – and its possible limitations.
Flash is quite literally portable sunlight. The beauty of flash is that you can point it in any direction, soften it, mix it, reflect it and even colour it if you want to. Learn to use flash as a more creative light source, perhaps even a supplementary one, rather than just pointing it straight at your subject and blasting away. Here are some techniques you can use.
Bounce your head
There is no worse light than straight, inyour- face flash. It’s harsh, cruel, cold and unflattering. And it’s the most common method of flash used, perhaps because most SLRs and compact cameras these days are being designed with pop-up flashes. You may well wonder if the camera companies are doing us any real favours. However, if you have an additional flash equipped with a bounce and swivel head, your days of ugly flash photos are over.
Flash illumination needs to be softened, and its direction needs to be changed to create shadow and dimension on the subject’s face. This can be successfully achieved by bouncing flash light off softer reflective surfaces. A white ceiling is the ideal example and is commonly employed. When this is done, the light appears more natural and the nature of the light itself is softer. By using a wide diffuser and a “catchcard” you can add some fill-light on the faces of your subject while still sending most of the light onto the ceiling for bounce. This little bit of frontal reflection will fill shaded areas such as the eye sockets and under the chin.
Flash can also be bounced off white walls or reflectors. This technique emulates window lighting, which is particularly flattering and natural. Sideways bouncing creates shadows on the face not unlike professional studio lighting and gives the viewer a greater idea of the subject’s dimensions. Exposure for bounce flash can sometimes be left to the automated sensors in the flash, but this usually results in underexposure. Therefore it’s best to allow for about one stop of light to be absorbed. Compensate by opening your f-stop up one stop. Also, be careful not to create a colour cast by using reflectors that are not white.
Off-camera flash
Often the most effective use of your flashgun is off-camera. In other words, the flash is not sitting on the camera’s hotshoe, but is physically disconnected. Synchronisation is achieved by using specially designed cords or leads which plug either into the camera’s PC flash connection or to the hotshoe itself. With dedicated flash systems, the manufacturer often provides the means by which the flash can be off-camera and retain full TTL (through-the-lens) metering.
Another way off-camera flash can be achieved is by using a flash with a slave unit attached. The slave unit senses the flash from another unit (maybe the one built into your SLR) and fires the flash to which it is connected simultaneously. By doing some calculation with guide numbers or by using a flash meter, you can establish your exposure settings. By having the flash off-camera, more natural lighting is attained and greater control over the image is granted. Simply changing the direction, distance and intensity of the flash can also make variations of the same image.
The unseen flash
Flash can be very effectively mixed with ambient light so that its effect is almost completely invisible, yet imperative to the image. This method is achieved easily by using the “rear curtain” synchronisation mode now available with many high-end system flashguns. Rear Curtain synchronisation is best used in conjunction with the TTL flash relationships that modern cameras have with their dedicated flashguns. This mode changes the timing of the flash so that it fires at the end of the exposure rather than at the beginning, by which time the camera’s exposure system has already gathered enough light for an ambient exposure.
The flash fires after that is achieved, ensuring that its illumination is not the overwhelming light source in the image. It’s a more natural approach to flash and provides a pleasing balance between the two possible light sources in the image.
Rear curtain flash techniques can be used to freeze subjects that might otherwise blur due to slow shutter speeds.
A photograph may require a shutter speed of 1/15th of a second to expose correctly. For moving subjects, this is disastrous. Rear curtain synchronisation will freeze the subject, while also allowing the blurred image to burn to film. The result is an image in which movement is apparent, but a sharp image is retained. For greater effect on action photographs, longer shutter speeds can be used to exaggerate the effect.
Top: Using straight frontal flash, the lighting is harsh and lacks a sense of dimension.
Middle: Bouncing flash off a white ceiling softens the light and creates a more natural and pleasing lighting effect.
Bottom: Bouncing the flash off a nearby white wall or reflector simulates window light and adds dimension to the face.
Macro flash
Flash is perfect for macro and close-up photography for several reasons. One of the greatest problems with close-up photography is a lack of depth of field, unless the ambient lighting is such that smaller apertures can be used. However, when smaller apertures are used, slower shutter speeds are required and this is not much help if you’re photographing insects or flowers that move in the slightest breeze. Because this is usually the case, your flash comes to the rescue. Incorporating flash provides the illumination, allows for greater depth of field and a faster shutter speed. The specular nature of the illumination also boosts colour and contrast and generally enlivens the image if needed.
Flash and digital
One of the great advantages of digital is the automatic white balance facility that allows the photographer to shoot using available light with any type of lighting mixture – ambient, fluorescent, tungsten etc. For this reason alone, we may see less apparent flash in images taken with digital cameras. However, for the reasons this article highlights, there may be creative and logistical reasons why photographers choose to fire their flashguns anyway. One of the disadvantages of flash with traditional film cameras is that the results can be unpredictable. When shooting digitally, experimenting with flash is easier and quicker, because you can preview the results on the LCD display screen.
Despite these advantages, digital cameras are gearing up for flash. Advanced digital cameras, such as the Olympus Camedia range, have for some time featured a PC-sync flash socket for studio or other external flash. The Nikon Coolpix 5000 even has a standard hot shoe and a menu set-up option to fire the internal flash at the same time as the accessory flash or to allow the accessory flash to fire by itself. Digital SLR cameras, of course, use the same principles for flash photography, except for TTL flash, for which most popular digital SLRs require specially-designed dedicated units that pre-flash to establish white balance.
By thinking of flash as the light source we use only when it’s dark, we limit our opportunities. Flash can be used to complement existing light sources, or can be used creatively as the sole light source in an image. Understanding flash has been the key to success for many photographers, and it can be for you. Think of it as portable sunlight – not a portable spotlight. Knowing when to use it – and when to leave it alone – is vital for the success of your photography.
Better fill flash
Fill Flash is a technique that’s been in use for many decades. Essentially it’s the use of flash illumination outdoors to fill harsh shadows, enhance colour and/or com-pensate for film’s inability to render detail in extreme shadows. With the automatic exposure and through-the-lens capabilities of modern systems, it’s become much easier to accomplish, but it’s beneficial to maintain control of your output to some degree. The methods of achieving this can vary depending on the flash system.
One easy way is to use the flash’s own sensors and fool them a little. To make fill flash appear a little less obvious, set your preferred aperture and shutter speed for ambient exposure and set your flash at a stop or two below the aperture you’re using (i.e. lens at f8, flash at f5.6 or f4). This fools the flash into thinking that it’s done its job, when in fact it has underexposed a little. For TTL flash, set the flash output at perhaps a stop or two below the standard TTL output. Remember to reset your flash settings once you’ve taken the shots.
Shelton Muller is the editor of Total Image. He can be contacted at shelton@total-image.com.au.
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April 19th, 2007
Is there a dedicated flash system that works with Ricoh? I have a stereo camera custom-built from 2 Ricoh XRX SLRs and want a dedicated flashgun. I have a feeling that Ricoh dedication was the same as Contax/Yashica. Is that so?
April 20th, 2007
I have a Minolta Macro Twin Flash set up with which I would like to be able to trigger a separate Minolta 5400HS flash unit to illuminate the background when doing studio shots. Any suggestions on how I can do this.
Bill Hogg