After hundreds of different bokeh lens tests using shiny objects and sunshine penetrating through trees, finaly I've rediscovered simple but pretty exact method that could hopefully be called CCRM bokeh test. It uses tiny bulbs glowing in the background that provoke bokeh circles that are easy to analise and compare. The distance for the main object was 0.5m for all 50mm lenses, and 1m for 105mm Sigma (with and without TC) and Sigma 50-500. White christmass bulbs were at 3m distance.
Object shot (HO steam model loco) was chosen for huge contrast, tiny details and very shiny parts that provoke easily CA and blooming. That way one can nicely judge other lens qualities besides bokeh.
What to look for?
According to the bokeh theory, single point out-of-focus light source should produce circular light "wheel" with uniform center to the edge brightness. More pleasant soft "light ball" with brighter center and dimmer edge could refer to slightly soft lens with unsufficient or unsimmetrical (front to back) sferical aberation correction. Brighter edge bokeh circles appear mostly with over-corrected (for scerical aberation) lenses. Additional tiny light circles inside bokeh circle are probably caused by spurious light reflections within the lens and contribute to unpleasant bokeh. Little less disturbing (at least for me) is poligonal bokeh shape due to partially closed iris.
These tests are just an introduction to REALLY controlled, comparative, repetitive and meaningful bokeh tests I plan to establish. Bulb crowded curtains will be used both in the back and in front of the object in order to check for both front and back bokeh, which are not neccesarily equally good or bad.