When shooting large group portraits, is there a trick to getting everyone to not blink (other than taking many shots)?
A couple other tips:
- Bounce flash, and don't use red-eye reduction mode for your flash
- Don't be predictable with when you take the shot. Some folks have a special talent for blinking at the wrong time, so don't let them know when the shot is happening
- Try to avoid having a bunch of other folks taking pictures at the same time. All those other flashes will cause people to blink.
Academic research has been done on this, and it even won an Ig Nobel Prize!
Piers then figured out how many shots I'd need to be 99% certain of getting a good one. He found that photographing thirty people in bad light would need about thirty shots. Once there's around fifty people, even in good light, you can kiss your hopes of an unspoilt photo goodbye.
Piers also came up with a rule of thumb for calculating the number of photos to take for groups of less than 20: divide the number of people by three if there's good light and two if the light's bad.
Some people are very good at "TTL blinking" -- they blink when they see TTL metering preflash, and make that just in time to ruin the shot then the flash fires for real. You can prevent that by pre-metering flash exposure. On Canon DSLRs it's done via Flash Exposure Lock (FEL), which is another function of AE lock button.
All flashes cause people to blink. Because many TTL systems today use a preflash, manual flash is a great way to avoid blinkers that sync up with the preflash-mainflash delay.
And to add to other techniques people have posted to get it in one shot, shoot several shots in burst and blending is a very seamless and easy way to get an immaculate result.