Canon: 7D: Flash Exposure Lock
Canon has this wonderful thing for flash, it's the E-TTL II system. With E-TTL II, you can control the exposure and the flash exposure separately. Basically, it sends a pre-flash to read the exposure across the 63 metering zones for what's dark (interpreted as background) and what's bright (interpreted as foreground). The problem is that I was looking to set the exposure and to lock that flash exposure for the rest of the photos.
The problem is where is the Flash Exposure Lock (FE Lock) button? I can't see it on the flash. I can't see it in the Canon 7D's menu. And of course, I didn't have any of the manuals with me.
- If the Flash mode is set to E-TTL II, you can press the <M-Fn> button on the top of camera to set Flash Exposure lock. Isn't it obvious?
- The FE Lock can be reassigned to the <*> with the C.Fn IV-1 function of the custom controls.
The Flash Exposure Lock stays on for 16 seconds, BUT, it's only for 1 (one) flashing. Second photo, you need line up the camera to the previous photo, with the same framing, press the Flash Exposure Lock a second time, then re-frame and take the photo. If you want another photo with the same flash exposure, it's the same procedure again. Each time you the <M-Fn> button, on top of the camera, the camera will fire a pre-flash.
- The Flash Exposure Lock does not work in Live View.
- Why not switch to manual and do the calculations myself? If the subject is static and not moving, yes it's easier and simpler, but it's impossible if the subject is moving and the distance varies. I can't calculate that fast, and by the time I adjust the power to fit the distance the subject is gone.