Brush size seen on screen is not the same as when put to use

Hi,

No matter which brushes I use - Adobe default, purchased or homemade - they will not come out full size.  I have set cursor preferences to full size and 50% to compare sizes but the results are exactly the same, ie. much smaller.  The cursor itself looks the same size for both settings and the results are always the same size - much smaller.  Good examples would be my signature brush, or my tree brush, ie. these are bog standard brushes, no jitter, no settings whatsoever, just lay down once, plain brushes.  The size I see on screen (adjusted with [ or ], or the brush size slider) is NOT the size that results when clicked into place. As stated above, both 50% and full size settings in cursor preferences result in exactly the same smaller size being laid down.  This is a real pain because one constantly has to CTRL+T to make things bigger if using a brush to place one item.  However, if using a brush to actually dodge and burn, or mask something, it's even worse because you cannot guarantee where and what you are masking, it's very pot luck.

I'm using a new high spec MacBook Pro, so this should not be an issue with power or graphics cards.

Any help would be greatly appreciated.  Thanks in advance.