Please take the time to read the following letter. It contains a wealth of information on use of the EOS D30 with the Canon Speedlite EX series flashes.
We hope you enjoy your Canon product for many years to come.
The EOS D30 has no sensor to read flash illumination reflected from the CMOS during exposure. If you want auto flash exposure through the lens, you must use one of our EX-series Speedlites. Top of the line right now is the 550EX, and we also offer 420EX, 220EX and Macro Ring Lite MR-14EX. (We had a 380EX that was replaced recently by the 420EX.) For more info on these products including specs, check out our web site at:
http://www.usa.canon.com/camcambin/cameras/speedlite/550ex.html
...and go from there. You can combine manual shutter speed and aperture settings with auto flash exposure on the D30 together with any EX-series Speedlite, and you won't have to dial down the flash exposure compensation unless you're trying for a special effect.
* When the lens is set for AF, E-TTL flash exposure is based primarily on the metering zone covering the active focusing point.
* In the case of FEL with the D30, flash exposure is always measured from the center of the picture area, with a metering zone that roughly corresponds to the partial metering circle in the viewfinder.
With these concepts in mind, the next issue is how to determine the active focusing point. The D30 offers 2 basic methods of focusing point selection: manual and automatic.
* When the photographer manually selects an individual focusing point, E-TTL flash exposure remains linked to that point regardless of changes in composition prior to exposure. This is why FEL is so valuable in 'focus lock & recompose' scenarios.
* When the D30 is set for automatic focusing point selection, the camera's algorithm for selection varies according to the user-selected AF mode. When One-Shot AF is combined with automatic focusing point selection, the camera selects the closest readable subject. When AI Servo AF is combined with automatic focusing point selection, the camera expects the photographer to identify the main subject. To do this, the outer focusing points are shut off at first. Once the center focusing point has picked up a subject, the outer focusing points are activated and the D30 is then able to track subject movement from the center to the left or right as well as from near to far or vice versa. When the D30 is set for automatic focusing point selection in One-Shot AF or AI Servo AF, E-TTL flash exposure tracks from point to point along with the AF system.
It's obvious that no single arrangement can work perfectly for every conceivable flash photo, but the range of settings available do cover the vast majority of typical shooting situations.
Here's an analysis of the choices:
1. When you're working with a still subject and there's plenty of time to set up the shot, consider FEL as the best choice because it allows complete freedom in composition under this situation.
2. For point-and-shoot simplicity with stationary subjects, consider E-TTL set for One-Shot AF together with automatic focusing point selection.
3. When you're working with subjects moving laterally across the frame and you are using flash, consider E-TTL combined with automatic focusing point selection. This combination of settings allows the D30 to give you as much assistance as possible in terms of placing maximum metering sensitivity, at the active focusing point.
The choice of One-Shot AF or AI Servo AF with automatic focusing point selection is up to the photographer, but we would suggest trying both to get a feel for how well they work in specific applications.
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Most of the reports we've been hearing from D30 owners indicate that auto flash exposure is very accurate with EX-series Speedlites including the 550EX, 420EX, 380EX, 220EX and MR-14EX as well as the built-in unit.
If you use any of these Speedlites in E-TTL mode, one of the most important considerations is ensuring that the subject you intend to meter is covered by the active focusing point when the flash is metered.
In standard E-TTL flash exposure mode, flash exposure is measured after the shutter button is fully pressed but before the camera's reflex mirror flips up. If you are using autofocus with the D30 and standard E-TTL on the 550EX, you will therefore need to use the Focusing Point Selector to cover your subject with the active focusing point before and during the exposure.
If you have gotten into the habit of locking focus using an individual focusing point, and then recomposing before the shot, you will almost certainly get a bad flash exposure in E-TTL mode with the 550EX or any other EX-series Speedlite. This is because the active focusing point is usually positioned over the background during exposure. There is a workaround, called "Flash Exposure Lock," or FEL for short. This feature allows the camera to memorize the flash meter reading from the D30's spot metering pattern by preflashing the subject using the AE lock button. Once this has been done, then recompose and shoot.
For details on both of these methods (E-TTL and FEL), please refer to your D30 User's Guide, Chapter 4.
You may find that you prefer slightly more or less fill than the 550EX provides at its default settings. If so, adjust the Flash Exposure Compensation setting and take some test shots using the LCD monitor to judge the results. We would also suggest that as a general rule of thumb, you should set the D30's Custom Function 10 to C.Fn. 10-1 at all times. This will put you in complete control of the flash exposure compensation setting and help to make your results more consistent and predictable, especially in outdoor fill-flash situations. Once again, this topic is covered thoroughly in the D30 User's Guide.
E-TTL compares pre-flash information with ambient metering data. It also uses the entire sensor for flash metering. Maximum emphasis is normally placed on the metering zone nearest the active focusing point, but that metering zone is considerably larger than the focusing point alone. It's also possible to get an "averaged" E-TTL flash meter reading by switching the lens to manual focus mode.