My bokeh tests are online, here:
* keeping camera-to-background distance constant:
Great work. It's really useful for me, who don't have the energy and time to do such detailed tests. I can't thank you enough for this.
Due to the vast information of your setup, the spot diameter on the background can be calculated and compared with the related visually result. The camera-to-background test is the one I am interested in as this simulates most sport scenarios.
At first I was surprised with the contrasting results of the 90mm @2.8 and 135mm @2.8
I wrongly assumed that you used an FF camera, which would have given the following results :
90mm @2.8 : spot diameter 1.96
mm , spot diameter with an infinite background distance : 2.92mm
135mm @2.8 : spot diameter 2.21mm
, spot diameter with an infinite background distance : 4.38mm
With an FF camera, in your scenario, the 135mm would blur the background more than the 90mm
Using a Canon APS-C camera, which I think it is what you have used in the test ( at least I hope so ! ) :
90mm @2.8 : spot diameter 0.91mm
, spot diameter with an infinite background distance : 1.88mm
135mm @2.8 : spot diameter 0.65mm
, spot diameter with an infinite background distance : 2.82mm
With APS-C, it's the 90mm which blurs the background more, and match with your visual results.
At enough background distance, the 135mm will always give more blurring.
Visually the spot diameter of 0.91mm produce a much better result than the 0.65mm. From my previous test (very rough estimates), I concluded that a 0.60mm - 0.70mm should give an acceptable blur, but one would still recognise what's in the background. The 0.91mm results in an unrecognised backgound (at least for me)
This shows why the big lenses in sports are so important. The 400 5.6 would produce some acceptable results, but won't achieve the unrecognised background blurring even when used on FF for a 2m hight subject. On the other hand, with a portrait orientation, or with a tight crop, this could be achieved.
Thanks again for sharing your work.