One is when you get regular smooth blur where light sources are stronger in the middle and fade towards edges of the circle.
The other is reversal of this, when the light sources appear weak in the middle.
this is the second and the third...

the third is like when you invert the second

but anyway, I'm the one trying to learn something here, so you tell me

what is donut hole bohek?


here are the examples of the 3 boheks I was talking about, not in the same order though, the one I'm interested in is the first one in the list on that site (the one with the hole in the middle of the object trace)

http://www.kenrockwell.com/tech/bokeh.htm