Use coloured lanyards to let people opt out of photographs
Not everybody likes having their photograph taken, and coloured lanyards make it easy for people to opt out.
At any conference, there will be some people who don’t want to appear in photographs. That’s fine, and you should give them a way to opt out. Approaches like “talk to an organiser” or “put a sticker on your badge” don’t really work – they scale badly, and if you take a picture of a crowd, it’s hard to see if anybody has the badge sticker.
Instead, some conferences use coloured lanyards to show whether you want to appear in photographs:
PyCon UK 2017 had blue lanyards if you were happy to appear in photos, yellow lanyards if not.
DjangoCon Europe 2018 was the same scheme, but black/white instead of blue/yellow.
XOXO 2018 had three colours: blue if you were okay appearing in photos or videos, yellow if it was okay but ask permission first, red if you didn’t want to appear in anything.
The key is having a bright colour that means “no photos please”. It stands out in a crowd, and makes it clear if you’ve accidentally snapped somebody who didn’t want their picture taken. It should stand out at a distance, and to somebody who’s colour blind.
Flash photography is a particular issue for some people (e.g. with epilepsy). It’s also distracting if you’re on stage and a flash goes off at the back of the room! You may want extra opt-outs for that; I know a few people who learnt that the hard way.
If you have children at your event (e.g. a young coder’s workshop), give all of them the “don’t photograph me” lanyard to avoid red tape around photographing children.