Question 2....
Is anyone able to get consistent results from the Canon Wireless Flash system? If so, are there any special techniques that you've found to be especially helpful?
OK, the canon e-ttl system is extremely accurate, but often misunderstood and misused. What I mean by that is the system itself actually takes a full shot by flashing the speedlights in a preflash at 1/32 power and looks at the actual result of the lights firing and determines the ideal settings for the full power shot, which means its not guessing, it sees what the lights are doing and than tells each light how much light to fire at the actual exposure while the shutter is open.
WOW! That's Great!
However, cameras do not know what you want the picture to look like and are attempting to make the entire image average 12% gray in overall luminance, unless you have dialed in a compensation factor at which it is attempting to make the image 12% plus or minus the compensation factor. This changes with different metering modes as a center weighted meter will tell the camera that the whole image should be equal to x, but the middle is more important and that should be given more priority so look at the whole frame and try to get as close as possible to the correct exposure but give up or add more to ensure that the center weighted area is in the right value. Same goes for spot only that gives priority to a smaller point in the frame.
So what's the problem?
Well the camera does not know what it is shooting, sadly while they can detect faces, and look for smiles (well some of them) they are not yet able to tell a bride from a polar bear or a groom from a penguin
Who cares?
Well it seems that many are shooting with these and not taking advantage of a special feature called FEL or flash exposure lock, that can guarantee a perfect exposure every time with flash because you can focus in close on skin and fel which fires a preflash and meters and if you know you want skin say 2/3 over you can dial that in and that exposure will be held by the camera for the next shot and can be held for several even if you recompose. And even if it is totally wrong it will still give you the same amount of light as long as you hold the FEL in the system. Why doesn't everyone use that it sounds great! Well it is great, but its not the most practical or even usable at times when things happen fast and you need spontaneity.
Now what is the typical scenario? you shoot a bride in a white gown and the face gets all dark and muddy, and the dress is dull and gray. or you shoot a groom in his black tuxedo and the face is too bright and the tux is a nice gray tone that seems to match the brides new dress. What went wrong?
Framing and a lack of the correct metering mode or not enough points to place the spot meter on the face of the subject which is likely the more important part of the shot and often very near to the 12-18% gray tonality that we all seem to be looking for with out meters. What the camera did was it fired a preflash and looked at a mainly white dress and determined that the image was brighter than the standard 12% and darkened it with the exposure/flash settings to make the image a happy mid gray in tonality, and for the groom in the black tuxedo the camera looked and said its way to much black and it needed to brighten the image through either exposure settings or flash power, and it again gave you an image that is overall a nice mid gray in overall tonality.
How do you fix it? Well you can spot on the face and set metering to spot metering, you can set manually but that kind of defeated the purpose of using the e-ttl system, or you can use center weighted metering linked to focus point, of course you can use FEL, and another option is to think ahead of what you are shooting and adjust the flash compensation manually, if shooting predominantly a frame fill with a white gown lower the flash exposure, or if its a dark scene brighten the flash exposure to the desired level.
Newer e-ttl also include a good old distance reading in there. What that does is say at x feet this much light hits the subject and once it knows how many feet from the subject you are based on the focus distance supplied by the lens (not all lenses and not all speedlights are compatible) it knows exactly how much light to put out to get a specific exposure (it varies this based on any compensation settings you may have adjusted) and that is always accurate so long as there is nothing blocking the light from hitting the scene.
Flashes like the Vivitar 285hv use a different approach they have a sensor in the flash itself that flashes until it gets enough light bounced back and shuts off the flash, that amount is determined by the settings you place on it like f5.6, f8, f11 at the given iso. This is accurate and works well and does not take into account what the camera is seeing but rather how much light is hitting the subject and returning to the flash. Main issue here is that they were designed with a tolerance for negative film and allow a variance of 1 stop over 1 stop under. Shooting slides or digital with the camera set to the same as the strobe will likely show you a result that is approximately 1/3rd perfect exposure, 1/3rd under exposed up to a stop and 1/3rd over exposed up to a stop. The latitude of film and raw can easily correct for this but its not the ideal if you are shooting weddings or events and have hundreds of images to proof. Wedding photographers have used this for years with negative film and never knew of the issue and now see it while shooting digital, why? because for most of them the lab processed and printed the film and adjusted the exposures for the correct overall values. But this is getting away from speed lights in general and off topic here.