Canon EOS Rebel T1i EOS System Brochure 2010 - Page 20

SPEEDLITE TECHNOLOGY Integral to the EOS System, Canon Speedlites are the ideal flash source for EOS SLR cameras. They are technologically advanced to provide perfect exposure and illumination with just about any subject, yet operation is remarkably simple. Whether you're an amateur or an expert, Canon Speedlites make it easy to obtain professional results. Sophisticated Flash Control Modes E-TTL-In E-TTL (Evaluative Through-The-Lens) flash exposure control mode, meter readings are taken through the lens, but not off the focal plane. Using a preflash fired after the shutter button has been fully depressed-but before the camera's reflex mirror goes up-E-TTL uses the camera's Evaluative metering sensor to compare the ambient light values with the light reflected from the subject by the preflash. The camera then calculates and stores the flash output required for optimum exposure of the main subject (as identified by the AF point) and the background. E-TTL requires the use of EX-series dedicated Speedlites such as the 580EX II, 430EX II, 270EX, 220EX, MT-24EX, or MR-14EX in combination with a compatible camera. E-TTL II-Available on Canon's EOS Digital SLR cameras, E-TTL II incorporates distance information from compatible EF lenses (see page 30 for details) for more versatile flash exposure control. E-TTL II minimizes underexposure that can occur with straight reflections by ignoring sensor areas that report abnormally high levels. This feature is useful when shooting a subject with a highly reflective object in the background, or if the subject itself is highly reflective. In addition, because distance information is used in calculating the flash output level, E-TTL II prevents overexposure when photographers lock focus and recompose. SPEEDLITES SLR Compatibility Camera Model EOS-1Ds Mark III EOS-1D Mark IV EOS 5D Mark II EOS 7D EOS 50D EOS 40D EOS 30D EOS Rebel T2i / T1i / XSi / XS EOS Digital Rebel XTi / XT EOS-1v / EOS-3 EOS ELAN 7NE EOS Rebel T2 / T2 Date EOS Rebel K2 / K2 Date E-TTL No No No No No No No No No Yes Yes No Yes E-TTL II Yes† Yes† Yes† Yes† Yes† Yes† Yes† Yes† Yes† No Yes Yes No A-TTL / TTL Not Possible Not Possible Not Possible Not Possible Not Possible Not Possible Not Possible Not Possible Not Possible 4-point / 3-zone 4-point / 3-zone Not Possible 4-point / 3-zone Speedlite Compatibility 580EX II 430EX II 270EX 220EX MR-14EX MT-24EX E-TTL / E-TTL II Yes†† Yes†† Yes†† Yes†† Yes†† Yes†† A-TTL No No No No No No TTL Yes††† No No Yes††† Yes††† Yes††† Manual Yes Yes No No Yes Yes † Not Linked to AF point. †† Requires EOS body that supports E-TTL and E-TTL II respectively. ††† Defaults to TTL in all conditions except direct flash in the camera's Program mode. High-Speed Sync - EF 135mm f/2.0L USM lens •f/2 •1/750 sec. For example, with the EOS-1D Mark IV, the ambient light is first measured using the camera's 63-zone metering when the shutter button is pressed. Next, a preflash is fired and the metering sensor takes readings. The ambient and preflash readings are compared. The metering areas having small differences are selected as the main flash exposure areas. Areas with large discrepancies between ambient and preflash readings are excluded or down-weighted because they are assumed to contain a highly reflective subject, or the subject is not in that part of the frame-an assumption validated by distance information. The algorithm thus helps avoid chronic underexposure problems in such situations. These readings are weighted, averaged, and compared with the ambient light reading and the main flash output is then set and stored in memory. The E-TTL II, in effect, captures the subject as a "plane" and not as a "point." As a result, EOS SLR cameras can help deliver consistent flash exposures even if the subject contains various colors and levels of reflection. The camera also allows the user to select an averaged metering pattern through custom function settings. TTL*-TTL (Through-The-Lens) is the standard flash exposure control mode used by the built-in flash units that come with some 35mm EOS film cameras. Unlike E-TTL or E-TTL II, TTL reads flash illumination reflected from the film during the exposure. When the camera is set to Program AE mode, TTL flash sets an aperture based on the ambient light level. Flash Exposure Lock (FE Lock) FE Lock adds Auto Exposure lock and Spot metering functions when shooting with EX-series Speedlites and E-TTL compatible EOS cameras. The EX-series Speedlite's preflash fires when the camera's AE Lock button is depressed, storing a Spot meter reading of flash and ambient lighting data for up to 16 seconds. This provides enough time to not only recompose the shot, but also alter the ambient light exposure for maximum creative control. FE Lock is extremely useful when you wish to recompose after focus lock or to place the main subject in a part of the frame not covered by one of the focusing points. It can also eliminate potential exposure errors caused by unwanted reflections from surfaces like windows or mirrors. Adjusting Ambient Exposure in FE Lock**-After preflashing the subject with the FE Lock button, ambient exposure can be adjusted by turning the Quick Control Dial. The ambient exposure level is displayed on the exposure level scale in the viewfinder and on the external LCD panel. Taken with MT-24EX and EOS-1v HS FP Mode*** FP (focal-plane) flash, or High-speed Sync, enables E-TTL and E-TTL II compatible cameras equipped with an EX-series Speedlite to synchronize flash at shutter speeds faster than the camera's normal maximum sync speed. Even in bright daylight, for example, a fast lens can be used at a wide aperture to reduce depth-of-field and emphasize the subject. FP flash can be combined with E-TTL, E-TTL II, or FE Lock, and is available in all AE modes plus Manual. Flash Exposure Compensation**** This setting adjusts flash output without changing the shutter speed or aperture. It's a particularly effective way to fine-tune the balance between foreground and background exposure for fill flash shots, but it can also be used to compensate for extremely bright or dark tones in the subject. Second-Curtain Sync Instead of firing the instant the shutter opens, Second-Curtain Sync fires the flash at the end of the exposure, allowing streaks of light to flow naturally behind a moving subject. This creative flash mode is most effective with slower shutter speeds and subjects with light sources, such as the headlights of a moving car. Stroboscopic Flash Stroboscopic flash is a series of flashes fired in rapid succession during a single exposure. With stroboscopic flash, multiple images of a moving subject appear in the photograph. Using this mode, you can analyze a golf swing or record the shattering of a windowpane. (Available with Speedlite 580EX II, Macro Ring Lite MR-14EX and Macro Twin Lite MT-24EX, the built-in flash of the EOS 7D). *ATTL and TTL are not compatible with digital SLR cameras. See lens chart for a listing of lenses that supply distance information. **Ambient exposure cannot be adjusted when the camera is set to Bulb mode or in low-light situations when the camera is set to Program AE or A-DEP. ***Unlike conventional electronic flash, FP flash output (guide number) decreases as shutter speed increases above normal X-sync speed. ****Flash 41 exposure compensation can be set with most current Speedlites, and it can also be set with all current EOS cameras other than the EOS Rebel series and EOS Digital Rebel.