I apologize for not remembering who originally posted this but it is so good I saved it to my tips folder. Whoever you are thanks a million.
Mike Morbach
The posts concerning problems with E-TTL persist, and I even get private emails with questions and concerns on the subject. I've experienced the same problems that others have with ETTL early on, and for a long time did not even bother with it, continuing to use autothyristor flash units for both personal use and work. However, the built-in wireless capability of ETTL intrugued me, so I dove in and spent a great deal of time and effort learning if ETTL really worked.
For those who have noticed my posts on the subject for the past six months or so, then you already know that I have found ETTL to be highly reliable, predictable, and consistent, PROVIDED one follows the rules and procedures for using it. It is NOT a simple, point-and-shoot procedure, although one can certainly become proficient enough to make it seem so. In fact, were I Canon, I'd just continue to put standard TTL systems in the film cameras. Digital is a different beast, because it's impossible to have a light meter on the sensor in the same way it is meter off of film. So should Canon just go with an old-fashioned thyristor flash for the built-in system on the digitals. Possibly, for the non-pro cameras, but I can just see the complaints about an "outdated" flash system!
The fact is, ETTL is essentially REQUIRED for the Canon digitals, unless one chooses to mount manual/thyristor third-party units, so we're better off learning to use it. And I have thoroughly enjoyed using it, too!
Here's the basic rules that need to be followed:
1 - Remember, ETTL meters ambient light and the subject receiving the flash illumination separately, and it does so through the lens. This is the biggest difference between ETTL and thyristor flash, which merely meters the entire area, and does so from the flash unit itself.
2 - For ambient lighting, the metering mode is whatever you have chosen at the moment. For flash, it is the ACTIVE FOCUS POINT. If your subject is on the left, then the left focus point should be selected to meter flash on the subject.
3 - Flash output is measured by pre-flash. Therefore, DO NOT focus, recompose, and shoot. This practice, common in non-flash shooting, is, I would bet, the most common reason for poor or inconsistent flash exposure. If you need to recompose, then focus and press FEL, which goes ahead and meters for flash, placing the correct setting in memory so that you can recompose and shoot.
4 - Because ambient light and flash exposure are metered independently, exposure compensation also operates independently. If you are outdoors, the best balance is achieved by underexposing flash by about 1 stop, so that it serves as fill only. (NOTE: I elect to DISABLE the custom fuction which automatically reduces for fill flash, since I find it tends to reduce too much. Instead, I make the reduction myself.)
5 - Although ETTL, whether using the active focus point or FEL, can provide predictable results, the photographer MUST anticipate times when the system will be fooled. If the subject is dark, for instance, then less light will be reflected back and the flash system will think it must put out more power, resulting in overexposure. Likewise, if the subject is white or highly reflective, then the system will underexpose the flash. Compensate accordingly. Or, meter off of something else using FEL. (Remember, FEL uses the CENTER POINT ONLY!)
This week, I shot some group and candid photos for a local Vacation Bible School. Using a D60 or D30 and either the 550EX or 420EX (no, I do not experience any difference in performance between the two), every frame was correctly exposed. (I tend to keep the camera on +1/3 ambient exposure and +2/3 flash, but cameras can vary. Outdoors, the flash compensation was -1.) The indoor shots were all bounced. At 1/125 and ISO 200, the flash is certainly providing the majority of the illumination. Outdoors, it was high noon with cloudless skies. Flash was essential. Most shots, I believe, were in Tv mode. Aside from the compensation for outdoor vs indoor, the only thing I did was manually selecting the focus point. None are FEL.
Mike Morbach
These are just candids, not meant to be award winners in any way, but meant to illustrate how I have been able to make ETTL work for me. Bouncing children and harsh sunlight aren't easy. Despite my years of experience using it, thyristor flash would not have been as effecient for the outdoor shots.
I rented a 550ex last night to fool around with and see how it
compares against my 420ex. I'd say about 8 out of 10 pictures were
underexposed. In manual mode, and without changing the exposure, I
shot some small objects of different texture all in the same corner
of my house, using the 28-135 IS and 50mm 1.8 lenses. When the
pictures looked properly exposed (about 20%) they looked fantastic!
I would frame a shot and then check the distance chart on the
bottom of the flash to make sure I was the proper distance from the
subject, and then fired away. I took two pictures of each scene, 1
without FEL and one with. In each case the pictures looked similar.
About 80% were underexposed - I believe I've been following the
documentation (and all the advice I've read here) properly. I
didn't really get into flash exposure compensation - Are there any
rules of thumb for exposure compensation?
From all the reading I've done, my underexposure problems HAVE to
be user error, dont they? Someone please help me get this figured
out - I really want to like this flash.
For those of you who say 'get the metz' will you please explain why
it works well for you?
