I'm still pleased with the simple and inexpensive YN460-II flash described previously. Sure, all it does is flash when told to do so and its flash power must be set manually; that is, no automatic flash exposure at all. But the YN460-II does these basic things well. Also noted previously, the YN460-II works with the Canon 7D camera even when the 7D popup flash is set for ETTL mode provided the YN460-II is set in its own "S2" mode. Again, "works" means only that the YN460-II fires with the appropriate timing -- its flash power is not set by the 7D flash controls.
After a few days of tinkering, I suddenly wondered "What if the YN460-II actually interfered with the 7D popup flash?" To test my loss of faith, I set up a simple scene with the faithful Woof-Woof and fired off several shots at varying conditions. First, the base case using only the 7D popup flash is shown below. The 7D was set for ISO 200 using manual exposure and 1/250 second at f5.6. The 7D was set to ETTL mode using the internal flash only and without flash compensation. Using the Canon 15-85mm lens at mid-zoom, I was perhaps nine feet away from Woof-Woof. The white balance was set for "flash" in Adobe Camera Raw.
I then tried the 7D with the YN460-II in several positions using bounce and direct flash at varying power levels. Not much to report here except that the 7D flash obviously does not know or care about the YN460-II. The 7D fires its preflash (which the YN460-II ignores), computes the "correct" flash exposure without regard to the YN460-II and then fires away -- joined this time by the YN460-II. In other words, the 7D flash does not instantaneously change its mind when the YN460-II fires.
To get the shot below, the YN460-II was placed a little behind Woof-Woof and aimed directly at him. The YN460-II was set to 1/32 power; the 7D internal flash was in ETTL mode and set at -3 flash compensation. White balance was set in ACR at the "flash" setting.
Throwing a simple second flash into the mix certainly can add a new dimension to a shot!