catchlights:

[magicmonkey]

ok, so how do you get a catchlight in someones eyes? The reflection of one of course! Do you need to blind them with a torch?

 

[tempra]

basically make sure that there is a light source reflecting from them, could be a flash, a window or the sun - you could use a torch, but they might hit you with it after a while!

 

[W.Smith]

basically make sure that there is a light source reflecting from them, could be a flash, a window or the sun - you could use a torch, but they might hit you with it after a while!

What tempra says, of course. But you can also paint 'm in later, in PP.
http://www.pl32.com/, for instance, has a nice spraygun for that.

 

[markc]

Personally I would avoid adding them with software. While it can give you nice catchlights, they won't match the light. People who have been into photography for a while will see the disjuction and will find it jarring. That's one of the same reasons why I usually don't like replacing a boring sky with a dramatic one. The lighting often doesn't match.

The eyes are acting like a convex mirror, so any light that is in front of the subject and not too far off to the side will show up in their eyes. They are often handy to use if you are trying to figure out how a photographer lit the scene.

 

[W.Smith]

Personally I would avoid adding them with software. While it can give you nice catchlights, they won't match the light. People who have been into photography for a while will see the disjuction and will find it jarring. That's one of the same reasons why I usually don't like replacing a boring sky with a dramatic one. The lighting often doesn't match.

The eyes are acting like a convex mirror, so any light that is in front of the subject and not too far off to the side will show up in their eyes. They are often handy to use if you are trying to figure out how a photographer lit the scene.

You're absolutely right, mark. I should have been more specific:
I'm not advocating creating catchlights – in eyes – where there aren't any*. That'd be weird indeed. But I am advocating 'amplifying' catchlights (if required/neccessary) in PP. I find that many photos that at first glance don't seem to have catchlights, in actual fact do have them if you look closely. Those can be 'amplified' in PP.

Example:

*in inanimate objects, like gem stones, etc., this is different, of course. But then we're not talking about 'catchlights', but rather about 'specular highlights'.

Example: