[Brightcolours]

 

So in a nutshell, this 25/1.8 looks like a supersharp lens from wide open (unlike many, if not most of 50mm FF primes) and until the diffraction creeps in. What's not to like?

Felix covered the 1st paragraph quite eloquently.

 

The rest is well explained by joachim.

 

I would just like to add: the 25mm f1.8 is only a 50mm f3.6 equivalent. Just about any FF 50mm is sharp at f3.5/f4.... Until the same diffraction sets in, of course.

 

The cheap Canon EF 50mm f1.8 II:



The Oly 25mm f1.8:



When you compare them at equivalent f-values, they are pretty similar in performance... You also see the diffraction loss being similar (Canon f8 vs Oly f4).