Today a reminder, prompted by my recent Montréal visit.
If your subjects do this:
…that is because:
- The flash is aimed straight at the subject (remember, outside, since you are majorly mixing flash with available light, you can get away with this if you need to); and
- TTL flash uses a pre-flash for metering. Then, a few ms later, when the shutter opens and the “real” flash goes off, your subject is already in mid-blink from the preflash.
Yes, you will recall there is a solution. Flash Exposure Lock (FEL, Canon) / Flash Value Lock (FVL, Nikon). This allows you to first press a button for the preflash, and then press the shutter for the picture and the “real” flash.
- Canon: use the “*” button, unless your camera has a little “FEL” or “M.Fn” button; then use that.
- Nikon: assign the FVL function to the Fn button (do this via the pencil menu). Note, D3100/D5100 cameras lack this function. Then use that button.
After pressing the button as per the above, you have a few seconds to fire the “proper” flash and take the image. Remember to warn your subjects there will be two flashes and the second one is the “real” one.
That little tip makes you a better photographer than uncle Fred. There. You’r welcome.