Often one reads about people suggesting that one should not use smaller than perhaps f/16 becuase of the distortion caused by diffraction. usually in connection with close-up work where depth of field is minimal and the temptation is to use the smallest aperture available to one.
As I understand it, diffraction is what happens when light goes through a small hole.
When I started photography seriously I was told to work at f/64 and I got nice crisp results, all else being equal.
But I am aware that P&S cameras rarely have apertures smaller than f/8.
This puzzled me until I worked out that f/8 with a 6mm lens has an aperture of 1.3mm diameter. But that lens I was using at f/64 was a 200mm which despite being worked at f/64 had 'a hole' of 1/8" approximately.
It was an 8 inch lens or 203.2 which gives 'a hole' of 3.175mm [ assuming the diaphragm mechanism was accurate ]
From all that I suggest that when one uses a longer lens with say a close-up lens for tight framing one need not be afraid of the diffraction gremlin ... becuase as Sporting Life said "It ain't neccessarilly so".
You would need to be stopped down to f/156 before you had the same aperture as the P&S.
I suspect there maybe a fly in the ointment of my argument becuase of the difference between long focus and telephoto lenses and modern compact zooms .... my 8" was a Rapid Rectilinear. A pair of 15" lenses used together.