Nikon Coolpix S50 has screwey autofocus when I shoot close-up. I select my subject, center it within my frame, depress the shapsot button half-way in order to initiate the autofocus function... The camera then begins to slide between out-of-focus, to in-focus, then keeps on going to out of focus again, and then slides "back" to an out of focus position! I understand that it is "looking" for the sharpest image as it does this--- but what it consistently selects is NOT the sharpest image! Ideas?

First off what do you mean by screwey autofocus? And how close up is close up? Have you tried changing the AF assist settings?
k Autofocus
Autofocus may not perform as expected in the following situations:
• Subject is very dark
• Objects of sharply differing brightness are included in the scene (e.g., the sun is behind the
subject and is in deep shadow)
• No contrast between the subject and surroundings (e.g., when the subject is standing in
front of a white wall, wearing a white shirt)
• Several objects are at different distances from the camera (e.g., the subject is inside a cage)
• Subject is moving rapidly
In the situations noted above, try pressing the shutter-release button halfway to refocus several
times, or use focus lock (c 99).
l AF-assist Illuminator and Flash
If the subject is poorly lit, the AF-assist illuminator may light by pressing the shutter-release
button halfway, or the flash may fire by pressing the shutter-release button all the way down.

Hi,
while shooting close up set ur cam on macro mode. Cam have focus range. focus range means the object distance from the lens
cam has focus range. For ur model on normal mode the focus range is 30 centimeter . anything placed between 0 to 30 cm will not be focussed and also close up range have focus i.e. 4 cm , anything placed between 0 to 4 cm will not be focussed....
by follwoing above rules, if u get the same problem, then there is a focussing problem in ur cam, get it serviced....
Hope this has helped you... Thanks....