紅圈L鏡, 一眼看穿? canon 85 mm lenses

from dcfever in 2018

set 1:

 

need to compare side by side the photos at 100%. Then compare the vertical and horizontal lines.

after comparing 5 different areas front and behind the subject, B has largest blur, so B is f/1.2. 

better to compare by gaussian blur spread, than just by blurriness

set 6:

85mm /1.4 has 9 blades, and f/1.8 and f/1.2 has 8 blades.

Clearly A is f/1.4

As the photos are not taken with max aperture, you cannot determine by size of bokeh ball. So you can only differentiate by rectilinear distortion, barrel / pincushion.

By subtracting B and C photo,

however the the picture are not taken in same direction, horizontal is shifted by 30 pixels, vertical by 38 pixels 

B has larger rectilinear distortion(barrel), is it's f/1.8. Also, the lower right bokeh is more like a ellipse eye than a circle, so definitely B is f/1.8.

C is f/1.2L

set 7:

by zooming in to 100%, B has highest sharpness/resolution: so B is f/1.2

for set 2,3,4,5, the photos are not taken at their widest apertures, but same f/2.8. So you cannot reliably judge by blur or bokeh. The differences can be due to (slight) optical design parameters.

You may find some hints by rectilinear distortion. Actually I found f/1.4 has quite nice bokehs when aperture is set at f/2.8

 

Overall, f/1.4 and f/1.8 are very similar in bokeh and blurs. But:

you get more rounded bokeh from f/1.4

from f/1.8 lens, the bokeh near edges are more "cat eyes"

you get higher resolution ( at infinity) from f/1.2

This quiz is a bit tricky, and only 2 questions (set 1, 2) are comparing under their widest apertures, which would show up the biggest characters (bokehs and blurs).

dofsimulator