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Canon 420EX Speedlite

Peter Kun Frary

Advantages of an External Flash

Why would you want to use an external E-TTL flash if your camera already has a popup flash?

  • First, even the smallest external Speedlite such as the 220EX is twice as powerful as the retractable flash. Thus, you have more power for group portraits or subjects posed against the setting sun.
  • Second, a shoe mounted Speedlite is less prone to red eye because it is further from the lens axis.
  • Third, Speedlites may be used off-camera on stands or brackets for better modeling and macro work.
  • Fourth, light modifiers, e.g., diffusers or bounce cards, may be employed for softer light.
  • Fifth, newer EOS cameras (A-Type) use the Evaluative pattern for external flash metering and, thus, yield more accurate metering than the 4-zone TTL pattern used for popup flash (DSLRs use Evaluative for both types of flash).
  • Finally, you may use special features of E-TTL flash, e.g., high speed sync (FP Flash) or flash exposure lock (FE Lock), not available on most popups.

Agashi at Aloha Tower Market Place • EOS 10D, EF 17-40 4L USM, 420EX Speedlite, ISO 800, Daylight WB, Av Mode (F4, 1/30), -2/3 FC.

The 420EX is a simple yet powerful flash: GN 138.6 feet at ISO 100 (42m), 24-105mm auto zoom head, near-infrared AF assist light, bounce and swivel, modeling light (slave mode only), flash exposure confirmation light (finally!), wireless ability, E-TTL II, E-TTL, TTL, second-curtain sync, FE Lock (flash exposure lock), flash exposure compensation and FP Flash (high speed sync).

You won't notice most of the above features as the control panel is rather barren: on-off switch, ready light, FP Flash switch, slave switch, channel selector and zoom position scale. There are no manual controls or LCD. FE Lock, flash exposure compensation, modeling flash, and second-curtain sync are controlled from the camera. And, yes, the EOS 1D, 1D MKII, 1Ds, 1V, 3, 10D and Elan 7 series have a full complement of E-TTL flash controls onboard. If you have a camera without such controls, e.g., Rebel Ti or Digital Rebel, you can still use the the 420EX in automatic mode, but cannot access all features (see the compatibility table at the bottom of this page).

Note: EOS models with a flash control menu--e.g., 40D, 50D, 60D, 7D & 5DII--are incompatible with most advanced features of the 420EX. The 420EX will work fine in auto mode and as a E-TTL slave, but second curtain sync and manual power settings are grayed out in the menu. Oddly, FEC can still be controlled from the camera.

Canon Speedlite 420EX mounted on stand

The 420EX is surprisingly small and light (300 g) for such a powerful flash. I no longer think twice about keeping a flash in my camera bag while traveling. I power it with four AA lithiums to keep weight as low as possible.

E-TTL Flash Metering

When you press the shutter button, the 420EX fires a low power preflash to determine flash exposure a split second before exposure. The preflash is so near the main flash it appears to be a single flash, not two flashes. The camera's Evaluative meter pattern is used to measure both ambient light and flash. In most modes the camera balances both flash and ambient light for a natural appearance. If you have an E-TTL II capable body, e.g., EOS Elan 7N or 1D MKII, distance information and other scene information may also be factored into the exposure.

Fill-in Flash

In bright light, above EV 10, the 420EX provides automatic fill-in flash in Full Auto and P modes. In dim light, EV 10 and below, flash is the main light in Full Auto and P modes (the background may be dark). Av, Tv and M modes deliver automatic fill-in flash in any light, even at night (slow sync mode). Slow sync results in a natural balance between ambient light and flash. You may need a tripod due to the resulting slow shutter speeds in slow sync mode.

Aloha Tower Market Place • Elan 7E, EF 50 1.4 USM, 420EX Speedlite, Fuji NPH 400 & Canonscan FS4000US. The Av mode and E-TTL metering did an excellent job of balancing flash with the strong backlight in this image.

Strangely, in dim light, the 10D, Elan 7 series and other recent A-Type bodies reduce ambient exposure in slow sync mode (e.g., Av or Tv modes at night). In light dimmer than EV10, ambient exposure is progressively reduced, reaching -1 one stop by EV 7 or so (varies according to ISO). The EOS A2, Elan, Elan II and IX don't exhibit this odd behavior. Maybe Canon considers ambient light underexposure a feature because it makes flash lit subjects stand out? I'd rather have no exposure reduction. The photographer should make the choice themselves. If you'd like to know more about this phenomena, visit the folks at the EOS Documentation Project. They even gave it a name: Flash Negative Evaluative Exposure Compensation or NEVEC.

The active focusing point is linked to metering and, thus, flash exposure. In other words, there is an exposure bias in favor of the object you focus on. This design also means you should avoid the lock-AF-recompose technique or suffer unpredictable results. Why? Flash exposure is determined at the moment of exposure (a split second before exposure for E-TTL and during exposure for TTL). If the active AF sensor is over something other than your subject--a black void--you'll get incorrect exposure. If you can't live without the lock-AF-recompose technique, Canon designed FE Lock for you (see below).

In the image below, I used ECF to select an AF sensor on the foreground subject and let the 420EX provide automatic fill-in flash in Program Mode (P).

Fort Vancouver, Washington • EOS Elan 7E, 420EZ Speedlite & Elite Chrome.

In the next image, I used ECF to select an AF sensor on the foreground subject but didn't use fill-in flash. There's a big difference!

Fort Vancouver, Washington • EOS Elan 7E & Elite Chrome (no fill flash).

As I mentioned above, the 420EX balances flash and background light perfectly in Av, Tv and M modes. There is an automatic flash reduction of -.5 to -1.5 stops depending on the strength of the ambient light. This balance makes the subject look natural, but is too perfectly blended with the background for some tastes and purposes, especially under dim lighting conditions. When I want the subject to standout from the background, I dial in +.5 or +1.0 of flash compensation or use P mode. P mode uses the flash as the main light--full power flash--under dim conditions (EV 10 or lower). Canon should make the before mentioned flash behavior clear in the manual as it is a source of confusion for many users.

FE Lock (FEL) & Flash Exposure Compensation (FEC)

FE Lock (FEL) is great for off-center subjects or troublesome highlights that fool the meter. FEL works like a spot meter for flash. First, place the center AF sensor on your subject and press the AE/FE Lock button. The 420EX fires a low power preflash. Exposure is determined by the reflectance of the subject in the partial metering circle, so be careful what you aim at. Use a medium toned area for best results. Finally, you have 16 seconds to recompose and shoot. The flash will expose the subject correctly even with usually light or dark backgrounds or an off-center subject.

Unfortunately, the FEL preflash isn't people friendly as nobody enjoys being flashed in the face once for metering and a second time for the exposure. If you shoot people images, you will be more popular if you apply appropriate flash exposure compensation and forgo FEL.

If you intend to use FEL on an unusually light or dark object, e.g., a white wedding dress, apply Flash Exposure Compensation (FEC) first because it doesn't work after FEL: subtract 1 to 2 stops of flash compensation for dark subjects and add 1 to 2 stops of flash exposure compensation for light subjects. Why? Spot or partial meters are calibrated to read 18% gray tones. No matter where you point, the camera expects a medium tone (18% gray) and gives you the correct meter reading for this result. However, FEC is easy to set on the Elan 7E:

1. You must be in the Creative Zone (P, Av, Tv, M) for FEC to work.

2. Press func (camera back) until the arrow (>) lines up with the Flash exposure compensation icon (lighting bolt with + -) on the LCD

3. Turn QCD until you get the amount of flash exposure compensation you desire (the -2 to +2 scale is on the LCD)

FP Flash

FP Flash allows you to sync at any shutter speed, albeit with loss of power. A 1/250 second exposure causes a loss of nearly half of the flash range (the Elan 7's normal sync is 1/125). However, this is great for daytime fill flash as it allows use of large apertures or fast film. FP Flash works best in Av, Tv and M modes where the user has control over aperture and/or shutter speed. When a Speedlite is mounted, P and DEP* modes are not shiftable making these modes almost useless for FP Flash. Moreover, P mode tends to favor smaller apertures over faster shutter speeds when a Speedlite is mounted. Second curtain sync does not work with FP Flash (high speed sync).

AF Assist Light

Focusing in the dark is quick and discreet thanks to the near-infrared AF assist light. With the 420EX mounted, low light AF is vastly improved: the Elan 7E or 10D will AF a blank wall in total darkness from nearly 30 feet away. You can disable flash and use only AF assist by setting a Custom Function on the Elan 7E (CF7) or 10D (CF5). Moreover, the 420EX is the only flash that works with all 7 sensors in Canon's 7-sensor array. The 220EX, 380EX, 430EZ and Sigma EF-500 Super only cover the center AF sensor. The 550EX and ST-E2 work with the 5 horizontal AF sensors only. Thus, as far as low light AF is concerned, the 420EX is the best flash for EOS bodies with 7 AF sensors: Elan 7E, Rebel Ti, Rebel 2000, 10D and Digital Rebel.

Flash Exposure Confirmation Light

The 420EX has a flash exposure confirmation light next to the Pilot Light. If flash exposure is accurate, it glows green for 3 seconds. If it doesn't glow, move closer and try again. This is a feature EOS shooters have waited years for. Hopefully, Canon will someday put a flash exposure confirmation light in the viewfinder of its cameras too!

Flash Exposure Averaging

If you disable AF the E-TTL program averages the overall scene for flash exposures. Why? There is no active AF point to link to. Although this may not seem like a good ideal at first, it works better than normal flash metering in certain situations. For example, a light colored subject with a dark background averages to "medium" and results in a perfect flash exposure. If you use FEL or lock the active AF point on a white dress the result is 1.5 to 2 stops underexposure (the meter is expecting medium tones). Of course, an experienced photography knows to dial in FEC at that point, but flipping the AF switch to off may be a simpler solution for some.

If you use the Exposure Lock button (*) for AF (via custom function 4), AF is not linked to the active AFpoint. Instead, overall scene averaged flash metering is used.

Portland Drinking Fountains are Akward • Elan 7E, EF 24-85 3.5-4.5 USM. FS4000US scanner. A popup flash is good for close fill but not much else.

Flash Compatibility

The EOS Elan 7 series has onboard E-TTL flash control fully compatible with all features of the 420EX. Other E-TTL capable EOS cameras are compatible with all or most of the features of the 420EX:

EOS SLRs and 420EX Compatibility

Model
Slave Mode*
Modeling Light
FEL
FE Comp
FP Flash
2nd Curtain Sync
E-TTL Metering
Lighting Ratios
D30, D60, 10D
20D, 30D, 5D
x
x
x
x
x
x
x
x
Elan 7 Series
x
x
x
x
x
x
x
x
Elan II/IIE
x

x
x
x
x
x

Rebel D/Ti/2000
x

x

x

x

Rebel G
x

x

x

x

1D, 1Ds, 1D II
x
x
x
x
x
x
x
x
1V
x
x
x
x
x
x
x
x
3
x
x
x
x
x
x
x
x
IX
x

x
x
x

x

IX Lite
x

x
x
x

x

40D, 50D, 60D,
7D, 5DII
x
 
x
x
x
     

*Only with a Master capable unit, e.g., ST-E2 or 580EX.

The 420EX is best suited for E-TTL/E-TTL II capable cameras but is compatible with older A-TTL capable EOS cameras in TTL mode only. TTL mode can't be used with the Elan 7E or other E-TTL capable cameras. Why? Users can't toggle between E-TTL and TTL. Instead, the flash senses the camera model and automatically switches to the appropriate flash circuitry. This is too bad as plain TTL is necessary for use with flash meters or optical slaves (E-TTL preflash causes premature triggering of slaves).

Pro and Cons of the 420EX

My only beef with this flash is the flimsy battery door. My old 420EZ and 430EZ both had metal hinges. Canon designed a cheapo plastic hinge for the 420EZ. Subsequently, take care when changing batteries, especially in cold climates. Fortunately, you may increase the 420EX's recycle time considerably over alkaline and lithium batteries by using rechargeable Ni-MH or Ni-Cad batteries.

If you shoot weddings or sports, or need manual control, get the 550EX or 580EX instead. Why? First, unlike the 430EZ, 540EZ and 550EX, you can't use Canon's external power pack and will run out of power after about 200 flashes. For most folks, the 420EX is more flash than they'll ever need. Plus, there is a gotcha with the 550EX: in low light only the 5 horizontal sensors of the Elan 7E work with the 550EX's AF assist beam. The 550EX beam pattern is optimized for the 45 sensor AF arrays of the EOS 3, 1V and 1D. The upper and lower sensors of the Elan 7 have trouble with the horizontal beam pattern.

In my view, the 420EX's main improvements over A-TTL/TTL units are FP Flash, FE Lock and wireless slave ability (with a 550EX or ST-E2). Plus, the 420EX is the only flash 100% compatible with 7-sensor AF arrays and, thus, is best suited for the Elan 7NE, Elan 7E, Rebel Ti, Rebel 2000, Digital Rebel and 10D. Like the Elan 7E, the 420EX is a balance of simplicity, power and features in a petite package you won't mind carrying anywhere.

Basic Specs

Guide Number (ISO 100): 23 m at 24mm • 42 m at 105mm

Coverage: 24mm-105mm (autozoom head)

Recycle Time: 0.1-7.5 sec (new alkaline batteries) • 0.1-4.5 sec (Ni-Cd)

Exposure Compensation: -2 to +2 in half stop increments (via on-camera controls only)

Exposure Modes: E-TTL II (with compatible bodies), E-TTL (Type A cameras), TTL (Type B cameras) & FE Lock (E-TTL only)

Flash Modes: Normal, High Speed Sync, Test Firing, Modeling Flash, 2nd Curtain Sync and Wireless Slave

Head: Autozoom with 90 degree bounce (up) and 180 degree swivel

AF Assist Light: Covers all 7 AF sensors of the Elan 7E, 10D, Rebel Ti, Rebel 2000 and Digital Rebel (partial coverage for EOS 1V or 3)

AF Assist Light Range: 7m for center sensor • 5m for periphery (I can often squeeze in another meter or two)

Batteries: 4 AA • Alkaline, Ni-Cd, Nickel-Hydride or Lithium

Weight: 300g (without batteries)

Size: 71.5mm (W) x 123mm (H) x 99.4mm (D)

Accessories: pouch, stand (with 1/4" socket) and instruction manual

Street Price: $175


  • *Some EOS SLRs allow shiftable DEP mode, e.g., EOS A2, Elan and IX, when a Speedlite is not mounted.

    If you're interested in wireless E-TTL flash, I wrote a review of the ST-E2 Speedlite Transmitter and 420EX here.

    A review of the 220EX Speedlite is here. A review of the 430EX Speedlite is here.

    6/1/2001 • Revised 2/25/2011

©Copyright 2001-2012 by Peter Kun Frary • All Rights Reserved

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