Haha, this is bound to start arguements, with people saying XYZ lens had bad bokeh and then offended owners defending their lenses.
Nathan wrote in post #16787863What constitutes bad or distracting bokeh?
Bad / Dristracting bokeh to me has repeating paterns, hard lines, a seenig double effect, hard edges to blurs, weird artifacts like onion bokeh in light sources, etc etc etc. There's lots of ways bokeh can be bad.
Nathan wrote in post #16787863What lenses render less than pleasing bokeh?
The sigma 35 Art produces less than ideal bokeh in the right (or wrong!) circumstances very easily. And yes, I own this lens.
The sigma 85 in generally looks very good from the samples I've seen, but every now and then produces some very strongly textured bokeh that I really don't like. I bought he 85L instead. Lot and lots of lenses have onion bokeh and other odd effects - even some of the best like the 24-70 f2.8 II and the 35L (both have onions). nice bokeh overal on both though.
Nathan wrote in post #16787863What factors in the foreground or background should we aware of that might create busy bokeh?
Busy bokeh tends to be worse with lots of small sharp lines or egdes -- things like tree branches, leaves, bark chippings, etc tend to give harsh bokeh on a lens that's prone to it.
Quick example from the Siggy 35 Art @f1.4. It makes makes my eyes hurt to look at this:
Nathan wrote in post #16787863What are composition considerations when it comes to bokeh?
I try to look for backgrounds that will make good bokeh. That depends on what lens you're using;
With the Siggy 35 i try to get the background far away / subject near enough to me to blur strongly enough to take the harshness out of it if I'm outdoors, but I hardly ever use it outside anyway, so it's not so much of an issue.
The 85L will soften most things, and I like to try to get some bright points in there for it to play with, so I'm normally looking for a high contrast background with small(ish) hard bright points, eg a side lit bush with some leaves catching the light strongly (see below). I considder the 85L to have basically perfect bokeh... however you can over do it and have 'boring bokeh'; it can destroy a background to such an extent it's just a coloured smear and this can look quite boring and bland, esp if it's nutural colours like concrete etc.
85L @ f2.5 :
when it actually makes your eyes hurt to look at it