Which has better background blurriness?APSC 50mm vs M43 75mm

Christof21 wrote:

Anders W wrote:

ageminmo wrote:

I was researching to buy a light combo for doing portraits and I enjoyed using GM1 with Olympus 45mm but I know the bokeh of Sony 50mm is better. The question now is when compared to Oly 75mm, which has more bokeh between these two cameras:

Any M43 camera with Olympus 75mm F1.8

versus

Any Emount APSC with Sony 50mm F1.8

COnsidering the effective aperture calculation for both?

I read that you can compare the background blurriness by dividing the focal length and the aperture.

So the Olympus combo will yield a ratio of ~42 and the Sony combo will yield ~28. That's a lot!

But they are from different systems, so if I will use their effective apperture..

Olympus 75mm will have 21[75/(1.8x2)] and SEL50 will have 18[50/(1.8x1.5)].

Then they are almost the same! WIth the sony combo, I dont need to be much farther to the subject and the body+lens combo is lighter. (Of course, I would be needing a good IBIS body like GX7, EM5, EM1, EPM2 etc and not GM1/GM5)

It's a bit more complicated than that. Which of the two will give more background blur depends on the magnification as well as the distance between the subject and the background. For example, for a head-and-shoulder portrait, the 50/1.8 on APS-C will give slightly more blur if the background is less than 2 meters from the subject whereas after that point, it is the other way around. You can experiment with other cases by means of this background-blur calculator:

http://howmuchblur.com/#compare-1.5x-50mm-f1.8-and-2x-75mm-f1.8-on-a-0.9m-wide-subject

The op has the correct formula (except that he made a mistake with the crop factor) for the background at infinity..

... but since background at infinity is but one possibility (and perhaps not the most likely one), the calculator is pretty handy.