Twiddle Dum and Twiddle Dee

Another Friday - weather dull and cold - time to conduct an indoor experiment....

What would happen if during a long exposure , I twiddled the zoom ring?

I practised this with a knight in shining armour stood in front of a painting. Sometimes I twidddled it in, and sometimes I twiddled it out. And sometimes I twiddled it in and out during the same shot.

Unfortunately, I can't remember what I did during this one. I think it was out (or even in).

Or both.

I suppose I could probably get an effect like this in photoshop. But I haven't got that.