CANONSCHOOL
Select the second wireless flash option as shown to ensure the camera flash only sends control signals to the remote unit
"Is it possible to use an EOS 80D to control a Speedlite 430EX III-RT without the pop-up flash firing?"
Michael Dahlhausen, Germany
BRIAN SAYS… The pop-up flash on the EOS 80D sends signals using visible light, so has to flash. But these signals occur just before the exposure, so shouldn’t have any effect on the picture. It does depend on the wireless settings for the built-in flash. In some configs the camera flash is fired as part of the exposure, in ratio to the Speedlite or with it.
When you select wireless function in the camera menu, make sure to choose the second wireless setting, so that the camera flash only sends control signals. You could also have a radio transmitter, like the Speedlite Transmitter ST-E3-RT, on your camera hotshoe to control the remote flash.
"In Aperture Priority with f/5.6, will the camera set the same shutter speed if I use an 85mm f/1.8 lens or 70-200mm f/4 at 85mm?"
Roger Boulter, Essex
BRIAN SAYS… If you have selected f/5.6 then the aperture is fixed and within the range of both lenses. Assuming your subject is identical, then the camera will set the same shutter speed. If you changed to a wide-angle lens you may see a change in the shutter speed since now the scene being shot is different, and with a wide-angle lens the scene is unlikely to be the same brightness. Specifically with a wide-angle lens you are likely to have more brighter sky in frame. This is the value of aperture numbers, they’re a measure of how much light is transmitted through the lens.