Photography is about creating images with light. For indoor, night, fill light, or certain special effects, using electronic flashes to generate light becomes an important component in modern photography. Canon flash units are called “Speedlites” by Canon. There are currently five shoe mount Speedlites (90EX, 270EX II, 430EX II, 430EX II-RT and 600EX-RT) as well as two specialty macro flash systems (MR-14EX II and MT24EX). While Canon consumer and prosumer DLSRs (such as the Digital Rebel Series and the EOS 7D MkII and 70D) have a small built-in flash, the pro series cameras such as the EOS 6D, 5D MkIII, 5DS/R and the 1D C cameras do not and so require the use of an external flash, often a hotshoe mounted Speedlite.
Flash illumination is produced by an electrical discharge though a glass tube filled with gas (often Xenon) at low pressure. This is a short burst of light, typically lasting 1/1000s or so. The amount of light which can be emitted is controlled by the size of the flash tube and the energy of the discharge. If full flash power is not needed, the discharge is “quenched” early. For example if the full flash takes 1/1000s and you only want 1/10th of that amount of light, the discharge is stopped after only 1/10000th second. The automatic metering system in the camera determines when the flash needs to be stopped to give the correct exposure. The color temperature of most flashes matches daylight, so they can be used for outdoor work to fill in shadows without the results showing “mixed lighting” effects.
“Speedlite” is the term used by Canon for its flashes. Not to be confused with “Speedlight”, the term used by Nikon for its flashes!
TTL stands for “Through The Lens” flash metering. In this mode (used only with film cameras), the light reflected from the film is measured by sensors in the base of the camera. When enough light has been received the flash is cut off.
A-TTL stands for “Advanced Through The Lens” flash metering. In this mode a weak pre-flash is issued, either from the flash tube when in bounce mode or from an IR emitter in normal mode. The intensity of the returning signal is used to estimate subject distance and to select an aperture for program operation. Final exposure is determined by measuring the amount of light reflected off the film, cutting off the flash when enough light has been measured. Again this mode is only available on film bodes, not digital.
E-TTL stands for “Evaluative Through The Lens” metering. In this mode the flash tube emits a pre-flash and the camera’s evaluative metering system is used to determine flash exposure. This not only allows more accurate flash metering, but also enables FEL (flash exposure lock) to be used, since the exposure is determined prior to the main flash firing. In addition E-TTL is required for digital SLRs because the digital sensor does not reflect light in the same way as film does and so TTL and A-TTL metering cannot be used. Only the “EX” series speedlites support E-TTL metering. The earlier “EZ” series speedlites only support TTL and A-TTL and so a cannot be used for auto flash operation with any EOS digital SLR.
E-TTL II is much like E-TTL except that the focus distance returned by the lens may, in some circumstances, be used in determining flash exposure. Since E-TTL II is a camera body based modification of E-TTL, all E-TTL capable speedlites can also operate in E-TTL II mode when used with an E-TTL II compatible body.
FEL stands for “Flash Exposure Lock”. It’s available on most both film and digital SLRs made after the EOS Elan II in 1995
FEB stands for Flash Exposure Bracketing. This is a function built into some high end speedlites (such as the 550EX, 580EX and 580EX II) which allows three images to be taken with different flash exposure compensation settings. It’s like AEB (auto exposure bracketing) for continuous lighting.
FP actually stands for “Focal Plane”, though some people think of it as “Fast Pulse” or “Flash Pulse”. In FP mode the flash tube emits a series of very fast flash pulses so that it appears to the film or sensor as a continuous light source rather than a very fast flash. This allows the use of fast shutter speeds, though it does reduce the effective power of the flash.
This is the fastest shutter speed at which the first curtain of the shutter fully opens before the second curtain closes. At speeds faster than the sync speed, the shutter actually forms a slit which moves across the image. The faster the shutter speed, the narrower the slit. If you make a flash exposure at 1/500s when the maximum sync speed of the camera is 1/250s, half the frame will be black. If you want to shoot using flash at 1/500s with that camera, you have to use FP mode (see above) if the speedlite supports it.
When a flash charges, a voltage appears between the center pin and the edge contact on the hot shoe foot. To fire the flash, a circuit in the camera connects these two contacts. The maximum sync voltage is the highest voltage that the camera can connect without damage. This also applies to the voltage across the PC connector socket. On many earlier Canon EOS bodies this was 6 volts, but on more recent models this has been increased to 250 volts. Canon speedlites conform to the 6 volt standard, but some 3rd party flashes (especially general purpose flashes not designed for EOS use) can have sync voltages of up to 250 volts, and a few are even higher.
Unfortunately Canon seem to hide the value of the maximum sync voltage for their SLRs somewhere in small print in the manual and sometimes they don’t list it at all, so n official comprehensive list doesn’t exist. What’s worse is that if you call their tech support you’ll often get a “6v” answer even if it’s actually 250v, and I assume that’s because the support reps like to play it safe if they aren’t sure. As far as DLSRs go, as far as I can tell, the D30, D60, 10D and original digital Rebel all have a 6v limit, while the Digital Rebel XT, the EOS 20D and newer DSLRs have a 250v limit. Despite some internet postings to the contrary, it appears that the PC socket and hot shoe sync voltages are the same.
The closest thing I have to an “official” list is from Chuck Westfall’s “Tech Tips” column from March 2007 (http://dirckhalstead.org/issue0703/tech-tips.html). It states the following:
Canon Digital SLRs safe up to 250 volts: EOS-1D Mark II N, EOS-1D Mark II, EOS-1Ds Mark II, EOS-1D, EOS-1Ds,EOS 30D, 20D, 5D,EOS Digital Rebel XTi, XT (400D/350D),EOS D6000/D2000, Kodak DCS560/DCS520 (circa 1998),EOS–DCS series (circa 1995).
I would assume that the 250v limit also applies to more recent DSLRs including all the current models.
Canon Digital SLRs safe up to 6 volts: EOS 10D, D60, D30,EOS Digital Rebel (300D)
Canon 35mm SLRs safe p to 250 volts: EOS-1V, EOS-1N, EOS-1, EOS 3
Canon 35mm and IX240 SLRs safe up to 6 volts: EOS 650, 620, 630, RT, 850, 750, 700, EOS Rebel Series, EOS Elan Series, EOS 10s, A2E, A2, EOS IX, IX Lite,T90
In normal flash operation the sequence of operation is as follows:
In second curtain sync the sequence of operation is as follows:
What’s the difference? Well say you have a moving car at night. In normal operation (first curtain sync) you get a sharp flash exposed image with the car lights trailing off ahead of the car during the remaining time the shutter is open. This doesn’t look right. What looks better is if the light trails are behind the moving car, and that’s what you get when using second curtain sync. You get the light trail during the regular exposure, plus the sharp flash image at the end rather than the beginning.
Not a Personal Computer connection as you might think, but a flash connector called a “Prontor/Compur” socket. “Prontor” and “Compur” are names of early shutters. Some think PC stands for “Push Connector”, but it doesn’t! PC flash connections are used for external flashes such as studio strobes. It’s actually an awful connector because the plug either falls out of the socket or gets stuck in it. It’s just a push fit, but were stuck with it now. There is a variant called a “Screwlock” PC connector and socket which gives a more positive connection because there’s a locking ring that screws into a compatible socket. Most of the Canon SLRs and DSLRs with a PC socket have “Screwlock” sockets.
Guide Number is a measure of how much light a flash emits. It can be used to manually set the correct aperture for proper exposure based on the distance between the flash and the subject. To find the aperture to use you divide the GN by the distance. So if the flash is 10ft from the subject and the GN is 40 (ft at ISO 100), you would set the aperture to f4 at an ISO 100 setting. The Guide number doubles when the film speed is increased by 2 stops, so that a GN of 40 (ft at ISO 100) is equivalent to a GN of 80 (ft at ISO 400). Guide numbers assume a direct path between the flash and the subject. If the flash is bounced off a wall or ceiling, all bets are off and the effective GN will be much lower.
The type “A” and “B” designations are sometimes used by Canon to differentiate between SLR bodies that support E-TTL (type “A”) and those that do not support E-TTL (type “B”). There are some additional subgroups, but basically it’s a measure of whether some sort of E-TTL is supported or not. All current EOS SLRs (both film and digital) are type “A” and all digital SLRs (except for the very early DCS3 and DCS1 models) are type “A”. All film bodies released before the EOS Elan II are type “B” and don’t support E-TTL.
Canon’s latest innovation in speedlite technology is the inclusion of radio triggering. Instead of using an optical signal to communicate between speedlites in a multiple flash system, RT speedlites use radio signals. Optical signals require that each speedlite can see the optical signals sent out out by the master controller. With RT technology speedlites can communicate around corners or even though walls! Range is increased (30m) and one “master” can control up to 15 other speedlites in up to 5 different groups.
Size – 3.1 × 5.6 × 4.9 in. / 79.7 × 142.9x 124.5 mm
Weight – 15.0 oz / 425 g
Price Class – ~$500
The 600EX-RT is currently (02/16) Canon’s “top of the line” hotshoe mount speedlite. Its features include radio triffering which can communicate with up to 15 compatible slave flashes in 5 groups over a range of 30m. It also has optical trigering for communication with Canon speedlites lacking in RT technology. Maximum guide number is 60 (m @ ISO100) when the flash head is fully zoomed out. At this setting it covers the field of view of a 200mm lens on full frame format. At its widest setting the 600EX-RT covers the field of view of a
The 600EX-RT has an extensive set of custom functions (23) and personal functions (7) which are described by Canon in the QuickGuide to Speedlite 600EX-RT
Size – 2.8 × 4.5 × 3.9″ / 70.5 × 113.8 × 98.2 mm
Weight – 10.41 oz / 295 g
Price Class – ~$300
The 430EX III-RT is based on the 430EX II (see below), but has the new Radio Triggering technology option for control of more speedlites over a greater distance than is possible using optical triggering. in RT mode it can act as a master or slave. It can also operate using optical triggerting, but only as a slave (like the 430EX II).
The 430EX III-RT is smaller, lighter and has a faster recycling time than the 430EX II and includes a number of new features including a larger rear LCD and a new scroll wheel. The Canon Speedlite 430EX III-RT also includes an SCF-E2 Color Filter which helps balance color temperature when shooting in incandescent lighting. Enhanced functions include broader bounce angle range and flash exposure compensation via the new control dial.
Size – 2.8 × 4.8 × 4.0″ / 72.0 × 122.0 × 101.0 mm
Weight – 11.29 oz / 320 g
Price Class – ~$200
The Canon 430EX II was introduced in the fall of 2008 and is a pretty full featured flash. The head zooms, tilts and swivels and the 430EX II can operate as a slave flash (but not a controller) in the Canon wireless speedlite system. The 430EX II is still in Canon’s lineup along with the more recently introduced Speedlite 430EX III RT.
Via an LCD panel and push button controls on the rear, full manual control is possible. The head can be zoomed to 24mm, 28mm, 35mm, 50mm, 70mm, 80mm and 105mm. There is also a manually operated “Wide panel” which pulls out and which expands the coverage to that of a 14mm lens. The zoom head can be programed via a custom function to take into account the “digital multiplier” factor of lenses used on a crop sensor camera. If the flash then detects a crop sensor camera, the head is zoomed to provide the correct angular flash coverage for the focal length being used. The output can be manually set to full, 1/2, 1/4, 1/8, 1/16,1/32 or 1/64 power and in auto flash mode the 430EX II can be set for up to +/- 3 stops of FEC (flash exposure compensation), set in 1/2 or 1/3 stop steps. If FEC is set on both the speedlite and camera, the speedlite setting take precedence. The 430EX II can be manually set in a high speed sync (FP) mode and for second curtain sync.
The AF assist beam of the 430EX II covers all 9 focus points of cameras such as the Digital Rebel XSi. EOS 50D and EOS 5D. Range is approximately 32ft for the center AF point and 16ft for the outer points.
On compatible cameras with a DOF preview button, depressing the DOF preview in flash mode will put the 430Ex II into “modeling flash” mode, where it will rapidly strobe for about 1 second to allow you to observe where any shadows will fall.
When the flash fires, color temperature information is transmitted to compatible Canon EOS DSLRs. This color temperature information is then used to set white balance if the WB setting on the camera is “auto” or “flash”. This can reduce image color variation between flashes.
The 430EX II is powered by 4 “AA” cells and Canon specify that between 200 and 1400 flashes can be obtained from one set of batteries. Recycle time after a full power flash is approximately 3 seconds.
Size – 2.8 × 4.8 × 4.0 in./72 × 122 × 101mm
Weight – 11.6 oz./330g
Price Class – ~$200
The Speedlite 320EX is the lowest cost speedlite with a lilt (90 degrees) and swivel (270 degrees) head. It’s powered by four AA batteries which should be good for at least 180 full power flashes. A unique feature of the 320EX is that it has a built in forward facing 75LUX LED light that can provide up to 3.5 hrs of continuous illumination for video work or can act as a fill light for bounded flash or as a modeling light. Maximum recycle time (after a full power flash) is 2.3 seconds. The flash head can zoom, with a maximum guide number when zoomed out iof 32 (m @ ISO100) and the flash covers the field of a 50mm lens on a full frame camera (32mm on an APS-C sensor camera). When zoomed back for maximum coverage it can cover a 24mm lens on a full frame camera (15mm on an APS-C camera) with a guide number of 24 (m @ ISO100). The 320EX can act as a wireless slave with any Canon DSLR or speedlite which has a master control function.
Size – 2.6 × 2.6 × 3.0 in./ 65.8 × 65.2 × 77mm
Weight – 5.5 oz./155g
Price Class – ~$170
The 270EX II is a lightweight flash with a guide number of 27 (m @ ISO100). It is powered by two AA batteries and has a recycle time for from 0.1 to 3.9 seconds (3.9s after a full power plash). Though the head doesn’t swivel it does tilt up by up by 90 degrees for bounce flash. It’s the least expensive speedlite that can be used as a slave flash with cameras (or other spedlites) which have flash master controller capability. The angle of coverage is good for lenses of focal length 28mm or longer on a full frame camera (17.5mm or longer on a camera with an APS-C sensor).
Size – 1.7 × 2.0 × 2.6″ / 44.3 × 52.0 × 65.0 mm
1.76 oz / 50 g$150
Price – ~$50
The Speedlite 90EX is the smallest, lighters and least expensive canon speedlite. It’s compatible with all Canon EOS cameras, but was released along with the mirrorless Canon EOS M camera as a small flash. The head is fixed (no tilt or swivel) and its coverage is good for 24mm and longer lenses on a full frame camera (15mm and longer on APS-C sensor cameras). The 90EX is powered by two AAA batteries which should be good for at least 100 flashes. Recycle time is 0.1-5.5 seconds (5.5 seconds if it has to flash at full power). The guile number is 9 (m @ ISO100). Though still listed on Canon’s website (02/16) the 90EX no longer seems to be generally available. Originally listed at $150, it can currently be found at some “closeout” websites at prices from as low as around $50.
Price Class – ~$550
The Canon Macro Ring Lite MR-14EX II is a specialty macro flash with a circular light producing area which fits around the lens. There are actually two curved flash tubes in the MR-14EX II and the power to each can be varied to produce anything from even illumination to a 6 stop difference. The MR-14EX II is compatible with both TTL and E-TTL and so can be used with both film and digital SLRs.
The MR-14EX II can also act as a master controller for a wireless flash system and can accept power from an external high-capacity battery pack. In addition to the flash tubes, which can also be used as modeling lights, there are two built in incandescent lamps which can both aid focusing and also act as modeling lights. It supports both FEC and FEB.
Compared to the original MR-14EX (MkI) the major upgrades are brighter LEDs for low-light focusing plus the ability of compatible DSLRs to control the ring light’s settings from the camera’s menu system.
Price Class – $830
Similar in concept to the MR-14EX, the
Price class ~$65
Price class ~$290
The ST-E3-RT can communicate over a 360 degree field at distances up to 30m (98ft) and can control up to 15 individual speedlies in up to 5 groups. The ST-E3_RT supports E-TTL II flash, manual flash, stroboscopic and auto external flash metering. It has a dot matrix LCD panel displays which all pertinent information simultaneously and has a backlit control panel
Price clase ~$200
Note that “Film only” indicates that automatic operation is available on when used with film based SLRs. With digital SLRs only fully manual operation (based on Guide Number) can be used with these Speedlites.
This was an early speedlite. Very basic, in fact so basic it didn’t even have an on/off switch! Fixed flash head, TTL only. Powered by a 2CR5 battery. Film only
A replacement for the 160E with a little higher power and powered by 4 “AA” cells. TTL only. Film only
The Guide Number of the 220EX is 22m or 72ft (at ISO 100), giving it a range, for example, of up to about 13ft at f5.6 at ISO 100, or 26ft at f5.6 at ISO 400. The 220EX has no provision for wireless operation. There is an AF assist beam which is projected when the light is too low for normal AF operation. It’s linked to the center AF zone of the camera and should be good to about 16ft. Recycle time depends on how much of the flash power is used during the exposure, but even for full power flash (where all of the power is used), it’s a relatively quick 2.5 seconds.
The main advantages of using an external speedlite like the 220EX is that it gives you more power than the built in flash on any camera (which typically have a guide number of around 12m @ ISO 100), it gets the flash head slightly higher above the axis of the lens (which may result in slightly less “red-eye”). You can also move the flash up to a couple of feet from the camera using the Canon off-camera shoe cord for even better results. Using an external flash also saves you from drawing flash power from the camera battery and so you can get more flash images per battery charge. The 220EX uses 4 “AA” sized batteries (alkaline or rechargeable) and can provide between 250 and 1700 flashes per battery set according to Canon.
Originally introduced for use with the Canon T90 camera, the 300TL is also compatible with EOS SLRs. Tilt and Swivel head with zoom (24-85mm). Supports TTL, A-TTL, FEL plus two manual power settings (full and 1/16 power). Powered by 4 “AA” cells. Film only
Fixed flash head with 28-70mm zoom. Supports TTL and A-TTL modes. Powered by 4 “AA” cells. Film only
Tilt and swivel flash head with 24-80mm zoom range. TTL, A-TTL and variable manual power (full to 1/32 power). Powered by 4 “AA” cells. Film only
Tilt and swivel head with 24-80mm zoom. TTL, A-TTL and variable manual power (full to 1/32 power). A replacement for the 420EZ with slightly more power and the ability to use an external power pack (the Canon Transistor Pack E). Powered by 4 “AA” cells. Film only
Most powerful and flexible speedlite that doesn’t support E-TTL. Tilt and swivel head with zoom (24-105mm). Supports TTL, A-TTL and variable power manual (full to 1/128 power). Stroboscopic operation to 100Hz. Flash exposure compensation of +/- 3 stops. Film only
A mid range speedlite which supports E-TTL as well as TTL and A-TTL. It has a head that can be tilted for bounce, but it does not swivel. The head zooms from 24-105mm. No manual power control. FEL and FP are supported with compatible cameras. Usable with film and digital SLRs. No wireless capability.
An upgrade of the 380EX to include a flash head that both tilts and swivels. Zoom range 24-105mm. Can act as a wireless slave. Supports TTL, A-TTL and E-TTL operation, but no manual power control. Has a modeling light, FEL and FP with compatible cameras. Usable with film and digital.
An update of the 420EX with slightly more power and variable power manual flash operation (full to 1/64 power). Flip out diffuser expands flash coverage to 14mm. Usable with film and digital. As of February 2009, the 430EX is still listed on the Canon USA website, though clearly it has been replaced by the 403EX II. There’s not a huge difference between the two models. The II version has a sturdier (metal) foot and with compatible DSLRs it can be configured from the camera as well as by using its own LCD panel. The 430EX II also has about a 20% faster recycling time than the 430EX and offers manual control in 1/3 stop steps.
Canon “top of the line” flash at the time it was introduced, the 500EX can act as a mater controller in a wireless flash system. Variable manual power (full to 1/128 power) as well as TTL and E-TTL operation. Supports FEL, FP, FEB and modeling light operation with compatible cameras. The 550EX has a high voltage connector for use with an external battery pack. Usable with film and digital.
An update of the 550EX, the 580EX offers slightly more power and some user interface improvements such as a control wheel. It has a faster recycle time than the 550EX as well as being physically slightly smaller and lighter. Usable with film and digital.
The 580EX II has more power then the 430EX II and the guide number (m @ ISO 100) varies with zoom setting as follows:
The 580EX II has about 35% more reach than the 430EX II.
New on the 580EX II is a external metering mode which does not use the camera’s metering circuit for exposure control. Instead a sensor on the 580EX II measures the amount of light being reflected back from the subject and controls the flash output accordingly. Of course this mode has been used on “semi-automatic” flash systems for decades as an “auto thyristor” mode. In the 580EX II it’s taken one step further when you’re using an EOS body such as the 1Ds MkIII, which tells the speedlite what ISO setting is in effect and what aperture is being used. With other cameras the ISO and aperture must be entered manually. There is no preflash in the external metering mode, which may be an advantage in some circumstances.
The 580EX II has 14 custom functions:
C.Fn-00: Distance indicator display (ft/m)
C.Fn-01: Auto Power Off (enabled/disabled)
C.Fn-02: Modeling Flash
C.Fn-03: FEB (Flash Exposure Bracketing) auto cancel
C.Fn-04: FEB sequence
C.Fn-05: Flash Metering Mode
C.Fn-06: Quickflash with continuous shot
C.Fn-07: Test firing with autoflash (enabled/disabled)
C.Fn-08: AF-assist beam firing
C.Fn-09: Auto zoom for sensor size (enabled/disabled)
C.Fn-10: Slave auto power off timer
C.Fn-11: Slave auto power off cancel
C.Fn-12: Flash recycle with external power source
C.Fn-13: Flash exposure meter setting
The ML-3 is a circular flash which fits around the lens for macro photography. The ML-3 is compatible with TLL operation but is not compatible with E-TTL and so is not suitable for digital SLRs.
The 480EG is a handle type flash (“potato masher”) rather than show mount. It had coverage for a 35mm lens, but came with clip on panels for 20mm and 135mm coverage. It was Canon’s most powerful speedlite with a Guide number of 68 (M @ ISO 100) when used with the 135mm Tele panel. Normal operation was via a PC connection and exposure was automatic using an external sensor. However it could be connected to the hotshoe of the camera using a special cord and in that mode TTL operation was possible. the 480 EG is not compatible with digital SLRs as it has no E-TTL capability.
Original text ©2009 Bob Atkins.