Canon EOS 70D: The Guide to Understanding and Using Your Camera (2014)
Chapter 19. Adding Illumination
We use a number of tools to manipulate and capture light; that is the very essence of photography. The primary challenge is being able to identify the important aspects of light, roughly quantify them, and then manage them to contribute to the final image. Studio shooting offers a (generally) consistent environment and spending some initial time evaluating and adjusting studio lighting can be much simpler than what the photojournalist, sports photographer, or birthday-shooter will encounter.
Characteristics of Light
There are simply too many ways to describe this characteristic of light. In the living room, we tend to express the amount of light a bulb can produce in terms of watts, which is really quite wrong: a watt is simply a measure of the amount of electrical energy consumed while the light is on. The more accurate expression of amount of light produced would be in terms of lumens. An incandescent bulb that consumes 75 watts of electricity produces about 920 lumens of light, whereas a 25-watt compact fluorescent light bulb puts out around 1,700 lumens. One of the older ways of expressing illumination is in terms of candlepower, with one candela (roughly the amount of light emitted by one candle) equal to 1 lumen per square foot. I saw a 40-million candlepower portable search light listed at Amazon.com. That’s just over one-half billion lumens.
At noon on a cloudless day, with a clear sky and relatively low humidity, the summer sun can be quite intense. Direct light from any source can be intense, even if it’s not as strong as the sun. For photographers, intense lighting is seldom beneficial, so we look for ways to tone down the intensity. That can be as simple as exploiting available features such as trees, walls, or shed roofs, or it can mean using more sophisticated devices such as scrims and reflectors, especially those that are portable and collapsible. Most reflectors also have a sheer or translucent panel to greatly soften the light.
The color of light varies based on its source, the environment, and the time of day. One of the problems with incandescent lighting is that the color of light changes as the bulbs age; color will also vary with the voltage. A 3200-Kelvin 120-volt bulb is going to be a bit yellow if you have only 110 volts to feed to it. Worse, if you plug a 500-watt photoflood into your already loaded circuit and turn it on, the voltage to the incandescent bulb may drop appreciably, further shifting its color toward yellow. Fluorescent bulbs may look alike, but the color of any given bulb depends on the coating on the inside of the tube, which is dependent on the environment it is intended for—office, bath, kitchen, etc. The color of sunlight can also appear different based on the environment. Sunlight pouring through the windows of a room with pink walls will be quite different from sunlight in a room with green walls. The color of sunlight at dawn or dusk is quite different from sunlight at noon, and the color will change when it shines through glass, even clear glass. Of course, air pollution also has a way of changing the color and intensity of light. One of the larger problems that we humans have with the color of light is that we tend to see it in comparison to other colors in the same scene, not as an absolute value. The camera sees light as a Kelvin value. Recognizing and correcting the color of light perceived by the camera takes a bit of practice (though there are some very good—and expensive—meters available to help with this), but the right color correction will make a great deal of difference in the final image, and it’s easier to correct while setting up the exposure than in Photoshop.
In terms of aesthetics, the direction of light may be the most significant of the qualities of light. (Can’t move the light? Then move the camera! Think in three dimensions.) Film was much slower than our digital sensors of today, and photographers learned to pose their subjects looking into the light source, with the camera between the light and the subject. The result was often an over-illuminated exposure of a grimacing, squinting subject, assuming the subject was not a field of corn. These pictures were often very two-dimensional, since any shadows that would have conveyed that third dimension were hiding out of view. That’s still true today if you use the straight-on approach to lighting, whether it’s sunlight, studio lights, or a camera-mounted electronic flash. Having your subject turn a few degrees left or right should help with this problem because it creates a degree of side-lighting which will greatly improve the perception of depth. Of course, if you’re working with portable illumination, you can simply move the light source to accomplish this same objective.
Natural lighting, in its simplest form, is daylight, either direct or indirect. Direct sunlight too often produces images with a narrow dynamic range; the highlights on light-colored surfaces are blown out, and detail is lost in strong shadows. There are a few techniques for helping with this situation (find some shade!), and there are a number of devices to help soften some of that direct sunlight. Some of the best natural lighting comes from sunlight reflecting off of a soft-colored wall.
If you do portrait, glamour, or botanical photography outside, you should use collapsible reflectors and diffusers, which can help redirect some of that light to compensate for strong shadows. Most come with gold, silver, or a mix of gold and silver reflective surfaces that allow you to introduce some degree of warming light. Translucent fabric can also soften direct light.
Natural light also includes things like moonlight or a bolt of lightning.
Man-made continuous illumination includes both intentional and unintentional sources. A portrait illuminated only (or primarily) by a campfire would be an example of intentional, man-made continuous illumination, as would a photo of a carnival illuminated by hundreds of different-colored neon and incandescent lamps. Any image illuminated by one or more lamps—be they street lamps, automobile headlamps, retail-store overhead fluorescent lamps, or the incandescent lamps of a residence—is using an intentional, man-made source of continuous illumination. For photographers, a common source of this type of illumination is their banks of studio lights.
An example of unintentional illumination includes the blackened, sweaty face of a firefighter illuminated by the conflagration, or the radiant smile of a four-year-old illuminated solely by the candles on her birthday cake.
In the early 1950s, I photographed some large, but totally black spaces: the insides of caves in Kentucky. With some very hot color slide film (ASA 25), I set up a Leica IIIf on a tripod, set the aperture to f/11 to achieve a decent depth of field, and set the shutter to stay open until I came back to the camera to terminate the exposure. Initially, with the shutter open, I could walk around with a flashgun, manually triggering a flash bulb in a variety of places until I had lit the entire room, a task that might have required more than a dozen flash bulbs for a single exposure. I am part of the “take only photographs; leave only footprints” school of nature conservancy, so the multiple flash-bulb model would have meant hauling a load of flash bulbs out of the cave with me.
I bought a small reel of metallic ribbon in a chemical supply store, and decided to experiment with it (though now I’ve learned that photographers had already been using it for over 100 years!). The metal was magnesium, which was about one eighth of an inch wide and about .001 inches thick. I cut about 8 inches off of the 75-foot reel, formed a hook on one end to hang the short strip inconspicuously, and repeated that in several locations within a room. When the camera was set up and ready, I’d walk back to each ribbon and ignite it with the flame from a carbide lantern. That much ribbon would produce about eight seconds of illumination, and at about 3500 Kelvin, it worked with our slow, color film beautifully. It was a very effective and reasonably inexpensive means of lighting those large rooms. I considered using flash powder, but could not find any of the old guns used for triggering the powder, nor did I want to breathe the smoke it would release. At that point, strobes were not yet available to photographers.
Fifty years ago, all electronic flash units were referred to as strobes. It’s surprising to see how many folks still use the term “strobe” to describe the electronic flash—speed light—that they use with their camera. True strobes are still available, and many of the upper-tier speed lights have a strobe capability built into them. The photographic use for a strobe almost always involves our need to capture several images depicting some form of motion, all in a single photograph. A typical application might include creating a single photograph of a golfer showing a dozen or so captures of his swing, from beginning to end. Another might be a sequence showing the different stances of a dancer as she progresses across a stage.
Electronic speed lights have certainly evolved over the past half-century. My first speed light was a home-built unit, but it matched the functional capabilities of the best commercial units pretty well. However, the need to keep a 400-volt battery ready, and to deal with two capacitors, each the size of a 12-ounce can of soda, was a lot; it didn’t travel with me too much. Now, I can get a small, extremely portable Canon Speedlite 90EX for $150 that produces more light, and offers features that my old speed light couldn’t. The Canon EOS 70D, 7D, 60D, and a couple of recent Rebels have small electronic speed lights built into the camera, and are capable of serving as a flash commander, optically coordinating multiple remote Speedlites distributed across as many as three groups.
In today’s world, it’s difficult to imagine the typical digital camera without some kind of electronic speed light. These speed lights have become smart enough to set themselves for mainstream automatic shooting, and also provide an extensive list of customizable options for personalizing your photography.
The latest in remote speed lights are radio-controlled units. Earlier units relied on encoded bursts of light for the camera-mounted commander to communicate with the remotes. Such an arrangement required that the commander be in line of sight with each of the remotes. Using visible light for this pre-flash communication also meant that human subjects might react to this light and have their eyes squinted shut by the time the true flash was triggered. In a radio-controlled speed light configuration, light isn’t used for communication, so the remotes can be placed anywhere within the operating range of the commander, without regard for drapes, walls, furniture, or any other visual obstruction. Both the optical and the radio-controlled systems allow for extensive arrangements of remotes, with up to three different groups of remotes supported in optical systems, and as many as five groups supported when using 2012-released cameras with radio control. All remotes in a group will be treated identically, but each group can be individually configured, which provides a significant level of lighting control.
As of writing this book, Canon lists the 90EX, 270EX, 270EX II, 320EX, 430EX II, and 600EX-RT Speedlites on its website for general photography, in addition to the MT-24EX Macro Twin Lite and the MR-14EX Macro Ring Lite. The two macro Speedlites are designed to encircle the lens and work very close to the subject. All but the 270EX are also capable of functioning as a remote unit (referred to as a slave unit by Canon) when managed by an optical-transmission commander unit (referred to as a master unit by Canon). The 600EX-RT and both macro Speedlites can function as both a Speedlite and a commander unit when attached to the camera’s hot shoe. The 90EX Speedlite can function as either a Speedlite or a commander unit, but cannot function as both simultaneously.
The recent 580EX and 580EX II Speedlites are also capable of serving as a dedicated external Speedlite, remote unit, or functional Speedlite and commander unit.
With the exception of the 600EX-RT, these units all rely on light to communicate between a commander unit and any remote units; the 600EX-RT has the ability to use either light (optical) or radio transmission for that communication. Using only light for a commander-to-remote communication is significantly less expensive than using radio transmission, but there are some disadvantages:
• There must be a line of sight between the commander and the remote; anything that blocks the light will interfere with that communication.
• The effective distance between the commander and the remote is limited to about 50 feet indoors and 30 feet outdoors (compared to about 100 feet indoors or outdoors for radio transmission).
• In optical transmission, a maximum of three unique groups of remote units is supported, but each group can have an unlimited number of remote units (all units in a group are treated the same, but are not required to be of the same model), whereas in radio transmission, as many as five unique groups are supported, with each group capable of controlling up to 15 remote units. Remember that remote units controlled by radio transmission must be capable of receiving radio transmission. As of the writing of this text, the 600EX-RT is the only Canon unit that meets that criterion.
• Canon DSLRs in the 1D series, the 5D series, and the EOS 6D do not have built-in flash units, and only a very small number of other models have a built-in flash that can also function as a commander unit. Thus, for many users, some kind of commander unit must be attached to the hot shoe, such as a Speedlite capable of also functioning as a commander, or either the ST-E2 Speedlite optical transmitter or the ST-E3-RT Speedlite radio transmitter. Both of these units are commanders only, with no electronic flash output.
• The encoded light flashes used for optical communication occur just before the main flash and can lead human subjects to conclude that the picture has been taken, allowing them to relax just as the main flash is triggered.
Currently, the variety of radio transmission-based Speedlites and accessories is quite limited, and the units are a bit expensive. The 600EX-RT is the only Speedlite currently available, and the ST-E3-RT is the sole transmitter unit available. The 600EX-RT can serve as a dedicated external flash, as an external flash with optical transmission commander capabilities, as an external flash with radio transmission capabilities, as a commander with either optical transmission or radio transmission capabilities (no flash output), as an optical-transmission remote, or as a radio-transmission remote. The ST-E3-RT serves only as a radio transmission commander, and must be attached to the camera’s hot shoe for full benefit.
Figure 19-1. Canon’s radio-controlled 600EX-RT Speedlite and related ST-E3-RT commander
On the left of Figure 19-1 is the Speedlite Transmitter ST-E3-RT, and on the right is the Speedlite 600EX-RT. This view masks the fact that the LCD panel for the flash is on the back of the unit, whereas the LCD panel for the transmitter is on the top of the unit. Note the similarity of the user interface for these two units. In the upper-right corner of the transmitter unit’s display, you will see an icon representing a radio antenna with concentric circles, while the display for the flash unit shows an icon for a lightning bolt, representing the optical transmission mode.
NOTE: Not all countries have the same regulations and specifications concerning radio frequencies and types of communications. In fact, Canon provides you with a list of countries that have yet to approve the use of this radio transmission technology (and some already have conflicting implementations, so there will never be approval to use this equipment in those countries). That extends to you and your travels: you have the responsibility to determine whether you are allowed to use this equipment in those countries. Canon also manufactures the 600EX for use in countries that have not approved the use of the 600EX-RT (the 600EX is for optical transmission only). Be careful: I’ve seen too many reviews, blogs, and other sources that feature an author who drops the –RT and uses the shorthand 600EX, obviously ignorant that a 600EX does exist, just not in the U.S.
Cameras released after January 1, 2012 (the EOS-1D X, EOS 5D Mark III, EOS 6D, and EOS 70D, but not the EOS 60Da) have a new hot shoe that allows a greater degree of communication and control between the camera and the attached Speedlite or commander unit when using radio transmission:
• The ST-E3-RT Instruction Manual states: “... you can shoot without any restrictions on the flash mode and maximum flash sync speed.”
• With these cameras, you have the ability to shoot with a different flash mode set for each firing group (ETTL-II for one group, Manual for another, Auto external flash for yet another).
• The modeling flash can be triggered from a remote unit.
• You can release the shutter from a remote without the need for any additional cables or remote control units.
• You can set the functions for Radio Transmission Wireless Shooting in the camera’s Flash Function Settings screen in the Shoot2 menu (earlier cameras require that you use the transmitter to set these functions).
• High-speed sync is available for these cameras, but not for earlier cameras.
Compared to the predecessor models 580EX and 580EX II, the 600EX-RT has improved weather protection, a greatly improved hot shoe latching system, a far simpler user interface, quieter recycling, a bit more power, and, of course, the radio transmission system.
With radio transmission, the sum of transmitter units plus Speedlite units must be 16 or fewer, including the unit in the camera’s hot shoe. However, in GR (Group) mode, you now have access to as many as five groups, allowing even better control over the functions of remote units.
Figure 19-2. The Speedlite 430EX II, shown on the EOS 70D