Why does flash sharpen photos so much?

Even using onboard flash I notice my photos come out much sharper.

Why is that?

Can I expect even great results with an added flash?

Increased contrast.

We perceive higher contrast as sharper.

Maybe the flash shots are coming out with a lower ISO than your nonflash shots? White balance may also be different, all of which you may consider 'sharpness' issues.

There is an outside possibility that it could also be the flashes ability to freeze the subject. If you are dealing with a small amount of camera shake or motion blur the flash will help hide or eliminate them.

edit: wow. My 666th post.

Scatterbrained wrote in post #12087650
There is an outside possibility that it could also be the flashes ability to freeze the subject. If you are dealing with a small amount of camera shake or motion blur the flash will help hide or eliminate them.

edit: wow. My 666th post.

The devil made you do it.

FlyingPhotog wrote in post #12087599
Increased contrast.

We perceive higher contrast as sharper.

Exactly.