[Brightcolours]

I've never seen so many uses of the word "swirly" before until then. I don't get this lens either. They're taking a defect and selling it? Ok, you get an interesting effect but it is a bit much for a one trick lens I think.

 

On a side note, I have noticed when using extension tubes on the EF 50mm f/1.8 for example, that gives it quite strong field curvature. I wonder if putting a negative power group on the front of a conventional lens then extending it could give a similar effect at much lower cost? If I'm bored I might try that this weekend.

Not unless those additions give loads of spherical aberrations...