This is the second part of a three-part series on Canon Speedlite flashes, written for the Canon Digital Learning Center by Gordon Lewis:
Choosing the Right Flash (click to read)
- Beyond the Instruction Manual
Multiple Flash and Lighting Ratios: A Wireless Primer (click to read)
Having once been a technical writer myself, I have great sympathy for the people who write instruction manuals. They often have to write while the product itself is in development and while the only samples available are prototypes. They also have to be economical in how they explain things. The idea is to tell you just enough to keep you out of trouble but not any more than you need to know.
An extra wrinkle for the guys writing Canon’s Speedlite flash manuals is that Canon’s flash system is so closely integrated with their EOS and Rebel cameras that the same feature can be set either on the flash unit, the camera, or both. They therefore have to be careful that their descriptions are accurate and consistent with each other. It’s a wonder Canon’s instruction manuals are as clear as they are.
That said, I’ve discovered that there’s more to know about how Canon Speedlites operate than you’ll find in their instruction manuals. I’m happy to pass along what I’ve learned. This tutorial will focus on Canon’s most full-featured unit, the Speedlite 580EX II, but as you see, a lot of this information applies to the 430EX II, and the smaller Speedlite 270EX and 220EX as well.
Speedlites will work with any of the following AA battery formulations. The type you prefer will depend on how you typically use your flash. Regardless of which you use, for best performance you should make sure your Speedlite’s batteries are fresh or fully-charged. Be careful never to mix battery types or to mix fresh with used.
AA alkalines: These are inexpensive and easy to find, but they’re non-rechargeable and recycle slower than lithium or nickel-metal hydride (NiMH) types. With fresh batteries and at close distances, however, the recycle times can still be within one or two seconds. Alkalines also have a low self-discharge rate, which means you can keep them in the flash or on the shelf unused for months at a time without worrying that they’ll die on you. This makes alkalines a good choice for infrequent use in non-demanding situations or as back-ups. (Do not store batteries in your flash for extended periods, however. They could leak and corrode the electrical contacts.)
AA lithium batteries: These are similar to alkalines in that they are non-rechargeable and have a low self-discharge rate. The difference is that they weigh less and provide significantly faster recycle times throughout their useful life. They’re also more expensive than alkalines or NiMH. These factors make lithiums a good choice for those who don’t use flash often but who expect top performance when they do.
AA NiMH batteries: These cost more than alkalines initially but save money in the long run because they can be recharged hundreds of times. They also provide faster recycle times. This makes them a good choice for the frequent user who needs top performance day after day.
Canon offers an external battery pack, the CP-E4, which adds an additional 8 batteries worth of power to your flash.
Along with the AA lithium batteries just mentioned, they tend to perform very well in cold weather conditions.
The one drawback of NiMH batteries is that they gradually lose power even when they’re not being used. Fortunately, there’s a new low self-discharge design available that can retain a charge for months. Whichever type you use, make sure they’re fully charged before an important shoot. Pros often carry one or two sets of fully charged backups, held together by rubber bands in 4 AA “clips.”
Canon’s Compact Battery Pack CP-E4: This is a good choice for when you need a high-capacity, heavy-duty yet compact power source for the 580EX II. The CP-E4 is powered by 8 AA batteries of your choice and attaches to the flash with a cable. Note that you’ll still need a separate set of batteries in the flash unit itself. When the 580EX II is in its default mode it will draw power from both sets of batteries. When I’m using the CP-E4 I prefer to use Custom Function 12 (for the Speedlite, not the camera) to set the 580EX II to draw power from the battery pack only. That way I still have a fully-charged set of internal batteries available if the pack runs low on power.
Distance Scale: Meters or Feet?
The default distance scale for the 580EX II and 430EX II is in meters. Those of us raised on the archaic Imperial system will prefer a distance scale measured in feet. To make the change:
- Turn on the Speedlite and hold down the Custom Function (C.Fn) button on the back for a few seconds until the C.Fn menu appears.
- On the 430EX II, use the +/- buttons to change the display to “Fn 00.” On the 580EX II, use the Select Dial to change the display to “Fn 00.”
- Press the Select/Set button once. The function number will blink on and off. If your Speedlite is currently set to display meters, what you’ll see is “Fn 00”, followed by a separate, blinking “0”.
- Turn the Select Dial clockwise (580EX II) or press the rear “+” button (430EX II) to change the rightmost 0 to a 1. Press the SET button again to lock-in the new setting.
If you have the either the Speedlite 430EX II or 580EX II connected to a compatible Canon DSLR, you can use the camera menu to alter the flash unit’s custom functions. Simply use the Multi-controller on the back of the camera to scroll to the appropriate Set-up Menu tab (with the yellow-colored “wrench” icon), then scroll to select “External Speedlite Control” or “Flash Control” and press the camera’s SET button. From there, scroll to “Flash C.Fn settings” (or similar wording). Use the SET button and Quick Control Dial to select C.Fn 0, and then change from meters to feet (Option 1).
Canon’s E-TTL II (Evaluative-Through-The-Lens) exposure system works by triggering a low power preflash that the camera measures to determine the actual exposure. If you have an E-TTL II-compatible camera (and if it was introduced after 2004, it probably is) the camera will adjust the flash duration based on the amount of preflash light reflected back from your subject and, if available, the focusing distance the lens is set to. The distance information provides more accurate results than reflected readings alone. Furthermore, with E-TTL II cameras, flash metering is no longer linked to the AF point you’re using — this reduces exposure errors if you prefer to lock focus and re-compose.
E-TTL and the current E-TTL II flash metering systems require a Canon EX-series Speedlite, as well as a compatible Canon EOS camera body. Several compact Canon PowerShot digital cameras, such as the popular G-series models, also can accept and work with EX-series Speedlites.
If you’re using one of the older Canon EOS film bodies, a modern EX-series Speedlite defaults to standard TTL flash metering, where there is no preflash and camera adjusts the flash duration in real-time. The flash unit’s instruction book refers to these as “Type B” cameras. Type B cameras include older film SLRs such as the original EOS-1, EOS-1N, EOS A2/A2E, and similar models from the early 1990s or before.
Considering that E-TTL II is completely automated, it works surprisingly well. It’s not infallible, though. When the lighting is tricky or your subject is brighter or darker than average, you’ll have to apply some human intellige·nce to get the best possible exposure. Here’s how:
Flash Exposure Lock (FEL): Just as in ordinary available-light photography, there are times when shooting flash pictures where it can be desireable to measure just a portion of the scene you're about to shoot, instead of the whole picture area. Situations where you're using a very wide-angle lens, and the subject only occupies a bit of space off to one side, are one example. Another might be if you're shooting a highly-reflective subject (even a bride in a white wedding dress), where you know from experience exposure can be thrown-off by the subject's clothes or surroundings. Flash Exposure Lock allows you to take a pre-flash reading off of a tiny area of the scene (such as a person's face, rather than their whole body), lock that reading into memory for at least 16 seconds, re-compose as you like, and take the shot.
Regardless of what metering pattern your camera is currently set to, Flash Exposure Lock readings are always Spot readings, measuring about 3% of the total picture area at the center of the scene. The only exception are some of the EOS Rebel models without a Spot metering option (Rebel XTi, XT, XS, and original EOS Digital Rebel); these take a slightly broader "Partial" FEL reading that measures about 10% of the picture area, again at the center of the viewfinder. You don't need to pre-set Spot or Partial metering on your camera. Just be aware that FEL readings will always be measured this way.
If the subject you aim the camera at for an FEL reading is noticeably lighter or darker than a middle gray equivalent, expect to dial-in some Flash Exposure Compensation before you shoot (see below).With most EOS cameras you’ll need to dial-in any necessary Flash Exposure Compensation before you take an FEL reading.
Refer to your camera manual to find out exactly where your camera’s FEL button is located. FEL readings are stored in your camera’s memory for as long as you keep the shutter button half-depressed; otherwise, it’s stored for up to 16 seconds or until you take a picture (whichever comes first).
FEL is also handy for checking whether the flash is outputting enough light for correct exposure. When you press the FEL button a green asterisk will appear to the right of the flash bolt icon in the lower left corner of the viewfinder. If the flash bolt icon starts to blink on and off, it means there isn’t enough flash power for adequate exposure at the current settings. You’ll either have to move the flash closer to the subject, use a wider f-stop, or narrow the flash’s angle of coverage (if appropriate).
Flash Exposure Compensation (FEC): Whether you work quickly with conventional E-TTL II flash metering, or use the fine control of Flash Exposure Lock (FEL), if your primary subject is brighter or darker than the average mid-tone, you’ll need to compensate the flash exposure accordingly. That’s where FEC comes in. This feature allows you to adjust your flash exposure upward or downward over a range of ±2 or ±3 stops, in 1/3- or 1/2-stop increments, depending on your camera and how you’ve set it up. All Canon D-SLRs allow you to set FEC before FEL, but some also allow you to set it afterwards. Check your camera manual for specifics.
Both the Speedlite 580EX II and 430EX II allow you to set FEC either using controls on your camera or on the flash itself. You’re free to apply Flash Exposure Compensation either way. If you happen to set FEC on both the Speedlite and your camera, the Speedlite’s FEC amount will override the camera’s.
Keep in mind that FEC is valuable even if you don’t use FEL, because it allows you to adjust your flash exposure separate from the continuous light exposure. Simply adjust the flash compensation up (+) or down (-) until the exposure is where you want it, based on the histogram and the image on the rear LCD. A flash exposure compensation symbol will appear on the top LCD and in the viewfinder as a reminder whenever you have FEC engaged. That said, either symbol is easy to miss if you’re not specifically looking for it.
If you’re wondering, the best way to control the background exposure is with your camera in manual mode. Use the exposure scale in your viewfinder to manually set the amount of over or underexposure you prefer. As long as your shutter speed is at or below the flash sync speed and your subject is within flash range, your Speedlite will automatically output the correct amount of light for your foreground subject.
Flash Exposure Bracketing (FEB): FEB automates the process of bracketing flash exposures over and under the recommended exposure to determine which is most accurate. This takes a few seconds to complete because the camera has to be set to single-frame advance and you have to wait for the flash to recycle after each exposure. It’s an exclusive feature of the top-of-the-line Speedlite 580EX II.
You can set the flash bracketing amount in 1/3 or 1/2-stop increments, depending on the amount your camera is set to. When the 580EX II is in its default mode, it allows a three-shot sequence of “normal, over, under.” Flash Custom Function 3 on the 580EX II allows you to change the sequence to “over, normal, under.” If you’d like to bias the bracketing toward the under or over-exposure side you can do so by combining FEB with flash exposure compensation.
Frankly, since a D-SLR provides instant visual feedback after each exposure, I find it easier to skip FEB entirely. If the flash exposure is too dark I use FEC to dial in 1/2- to 1-stop more flash output. If it’s too light I do the opposite. But if you’re in a situation where you need a choice of flash exposures, FEB does provide a method to quickly achieve this, without having to pull your eye away from the viewfinder in-between shots.
Keep in mind that Flash Exposure Bracketing is entirely separate from Auto Exposure Bracketing of ambient light, which nearly all EOS digital SLRs offer. In-camera AEB is always disabled whenever you attach and turn on a Speedlite, and therefore it cannot be combined with Flash Exposure Bracketing.
The focal-plane shutter in a D-SLR has two curtains, one of which covers the sensor. At exposures above the camera’s maximum flash-synchronization speed (let’s use 1/500 second for example) the first curtain moves across the sensor, followed a few milliseconds later by the second curtain. This creates a gap between the two curtains. It is this gap traveling across the sensor that exposes the sensor to light.
When the shutter is at or slower than its maximum sync speed, however, the first curtain will travel completely across the sensor before the second curtain closes behind it. The instant between when the sensor is completely uncovered but before the second curtain starts to close is when the camera triggers the flash unit.
High-Speed Sync: You would normally not be able to use an electronic flash unit at high shutter speeds because the sensor is never fully uncovered by either curtain during the exposure. All Canon Speedlites, however, have a high-speed sync feature that will cause the flash to pulse repeatedly as the shutter curtain “gap” travels across the sensor.
The “catch” is that these light pulses are of short duration and therefore result in reduced output and range. The higher the shutter speed, the shorter the effective flash range. Setting a higher ISO won’t help extend the distance range, unless your camera is in the Manual exposure mode, because the result will be a higher shutter speed and/or a smaller aperture. You’ll find that in practice high-speed sync is most useful at close distances, for flash-fill and for macro lighting.
Second-Curtain Sync: When your DSLR is in its default mode it will trigger the flash the instant the 1st curtain is fully open. This works just fine in most situations, but you may occasionally want to “drag the shutter” by leaving it open long enough for the ambient light to record an image. At low light levels the shutter speed may be 1/8 second or more—long enough for anything in motion that isn’t illuminated by the flash alone to be recorded as a blur. When the motion is roughly parallel to the focal plane the blur will appear to be ahead of the sharp, flash-exposed subject. When the camera is set to 2nd-curtain sync the blur will appear after the subject, which looks more natural to our eyes.
Both Second-curtain sync and High-speed sync are set by pressing a button on the rear of the Speedlite (it toggles between normal operation, Hi-speed sync, and Second-Curtain sync, each time the button is pressed). It can also be set on the camera’s Flash Settings menu, if you’re using the 430EX II, 580EX II, or new 270EX along with a recent EOS digital SLR which supports this feature. Second-curtain sync is indicated by an icon with three right-facing, overlaid arrows, with one arrow filled-in and the other two “hollow”.
Keep in mind, however, that if your subject is moving toward or away from the camera, there can be a significant change in distance between the time the 1st curtain opens and the 2nd curtain closes when you’re using slow shutter speeds. Although your camera’s servo autofocus mode will automatically maintain focus, the change in distance may result in over- or under-exposure because the preflash measurement is based on the initial distance. The solution is to move further away or to keep the motion, even if self-induced, parallel to the film plane.
There are, of course, many more features available on Canon’s top-of-the-line Speedlite 580EX II—more than I can explain in this brief tutorial. That’s why the third tip (coming soon) in this series is be dedicated solely to how the make the best use of its wireless flash mode. This will include a clear explanation of how its wireless flash control menu is organized, how to use multiple flash units, and the difference between lighting ratios and reflectance ratios. Don’t miss it!
Want to master Flash Photography with the EOS System? Try a Canon Live Learning Workshop: You’ll discover how to use Canon Speedlites to create and control the perfect light for a variety of situations. From basic flash photography concepts to multi-flash creative techniques used by professionals, our Speedlite workshops will help you bring your photographs to life. Industry experts/pro photographers will demonstrate techniques that can be applied to a variety of scenarios including portraits and still-life. You'll work in a professional photo studio with experienced models to ensure you leave the workshop with gorgeous images and a firm understanding of the Speedlite system. Learn all about
- The core concepts of flash photography and the EOS Speedlite System
- Essential lighting and flash exposure control
- Creative lighting techniques (including the E-TTL Wireless System)
To learn more, or to register for this and other upcoming Canon Live Learning classes and workshops, click here: www.usa.canon.com/canonlivelearning
Writing and photography by Gordon Lewis. Gordon has over 30 years of experience as a professional photographer and Canon user. His photographs have been published in major U.S. photo magazines and national ads. To see more of Gordon's work, visit his Shutterfinger blog or his online gallery.
The CDLC contributors are compensated spokespersons and actual users of the Canon products that they promote.
All images are copyright Gordon Lewis
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