It's not expected but definitely appreciated.
Generally, it's not expected that you will tip your photographer but there are times when it could be good and photographers will always be grateful.
Do you tip a wedding photographer?
A wedding photographer would be the most likely photographer you would tip. There is a lot that goes into wedding photography. They work with clients for months in advance, work with many other wedding vendors, spend all day at the wedding, and have all of the stress of making sure they get all the photos right since you can't reshoot a wedding.
Suffice it to say, your wedding photographer probably deserves a tip, but it's not mandatory.
Do you tip family, senior, and engagement photographers?
Similar to wedding photographers, family, senior, and engagement photographers are all pretty hands-on and may do more than you think. In addition to taking and editing the photos they also do location scouting; secure needed photo permits; pack, transport, and carry all of their equipment (light stands are heavy); have studio upkeep; and more.
While it still isn't expected, tipping your family, senior, or engagement photographer is certainly a kind thing to do.
Do you tip other kinds of photographers?
When working with photographers for headshots, mini-sessions, or real estate, tipping isn't expected.
When else do you tip photographers?
The best time to tip a photographer is when you feel they've done a great job! Tipping shows gratitude for hard work and going the extra mile. If your photographer has done this, then you certainly could give them a tip. Just remember that in some countries and cultures tipping practices may be different.
Alternatively, consider leaving a positive review on the photographer's website or Google business page. Reviews mean a lot to photographers and is a great way to share your appreciation.
Should you leave a tip after the photoshoot or once you receive your photos?
There really isn't a set answer here. But since tipping shows gratitude for a job well done, logic would dictate you give a tip once you've received your photos.
The one exception to this would be for wedding photographers. Tipping your wedding photographer at the end of a long wedding day would definitely be a kind gesture and a way to show gratitude.