I posted this as a reply in a different forum and thought it might make a useful reference here.
Keep in mind I'm not a "traditionalist" when it comes to light - I do what looks right to me. So these aren't CLASSIC in any strict sense but they're close to the classic styles described.
Here's BUTTERFLY LIGHT - signified but the butterfly shape of the shadow under her nose. Shot with 22" beauty dish and fill from the paper bg. Fairly low contrast since the shadows are minimal. Still not flat since her face has clear dimension:
Here's SHORT LIGHT - (meaning the key is on the short side of the face where no ear is showing). Shot with 36"x48" soft box and fill from reflections in the room. The ratio is easily 4:1 or more here - very contrasty shot:
Here is CLAM SHELL or GLAMOR LIGHT - shot with a 48" Octabox 18 inches away above and slightly off axis and a reflector 12 inches below her chin (the light and reflector make a "clam shell" shape). This is silky smooth light - great for women since it hides blemishes.
Notice while it's low contrast it's not flat (again her face has clear dimension):
This is REMBRANDT LIGHT - has that "old masters" look with the light almost behind the subject and the classic loop nose shadow on the cheek. Shot with 48" Octabox and reflector for some fill. I chose a very dark/moody processing for this one:
Here is BROAD LIGHT - meaning the key is on the broad side of the face. Best for men/boys. Shot with 36"x48" soft box and white foam core for fill. Never use this style with wide faced people or overweight people - it will exaggerate their facial width and be quite unflattering:
For those starting out with lights - keep it simple. Use only 1 light and work it every way you can imagine until you "own it" (meaning you know it so well you can almost see the image before it's shot). Then and only then should you add a second light. I have been using studio strobes for about one year and I've yet to take a shot with 2 lights.
Hope this is helpful.
Keep in mind I'm not a "traditionalist" when it comes to light - I do what looks right to me. So these aren't CLASSIC in any strict sense but they're close to the classic styles described.
Here's BUTTERFLY LIGHT - signified but the butterfly shape of the shadow under her nose. Shot with 22" beauty dish and fill from the paper bg. Fairly low contrast since the shadows are minimal. Still not flat since her face has clear dimension:

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Here's SHORT LIGHT - (meaning the key is on the short side of the face where no ear is showing). Shot with 36"x48" soft box and fill from reflections in the room. The ratio is easily 4:1 or more here - very contrasty shot:

Subscribe to see EXIF info for this image (if available)
Here is CLAM SHELL or GLAMOR LIGHT - shot with a 48" Octabox 18 inches away above and slightly off axis and a reflector 12 inches below her chin (the light and reflector make a "clam shell" shape). This is silky smooth light - great for women since it hides blemishes.

Subscribe to see EXIF info for this image (if available)
This is REMBRANDT LIGHT - has that "old masters" look with the light almost behind the subject and the classic loop nose shadow on the cheek. Shot with 48" Octabox and reflector for some fill. I chose a very dark/moody processing for this one:

Subscribe to see EXIF info for this image (if available)
Here is BROAD LIGHT - meaning the key is on the broad side of the face. Best for men/boys. Shot with 36"x48" soft box and white foam core for fill. Never use this style with wide faced people or overweight people - it will exaggerate their facial width and be quite unflattering:

Subscribe to see EXIF info for this image (if available)
For those starting out with lights - keep it simple. Use only 1 light and work it every way you can imagine until you "own it" (meaning you know it so well you can almost see the image before it's shot). Then and only then should you add a second light. I have been using studio strobes for about one year and I've yet to take a shot with 2 lights.
Hope this is helpful.