Well, by popular demand, I came up with a quick blind comparison to compare the bokeh between these two lenses.
- Shot on a tripod from the same spot, though I can't rule out some minor perspective shift by bumping it while changing lenses.
- In order to normalize the DOF between the two, the FA 31 was shot at f/1.8, Sigma 35 was shot at f/2.0 (the Sigma will have shallower DOF at the same aperture due to its longer focal length).
- Both were shot with Hoya Pro-1 Digital 3-stop ND filters.
- Manually focused on the leaves. Upon close examination afterwards, I found that the focus was very slightly off between the two shots, which you might notice in the surrounding leaves.
- Exported from Lightroom 5 using default settings, except that I manually normalized the white balance on both to "Daylight" (AWB on the K-5 gave slightly different values). Any difference in color is presumably due to the lenses themselves.
- I cropped the FA 31's shot in Photoshop to match the Sigma's FOV as close as I could get, then resized them both for the same final output size. This also means that the vignetting and distortion on the FA 31 is slightly lower than it would be in an uncropped shot.
Try not to pay too much attention to the differences in lighting and the position of the leaves. There was a significant breeze that day, moving clouds and I was standing at the edge of the shadow of a building behind which the sun was setting (so I could see the LCD). In the time it took me to change lenses, put on the ND filter, and reshoot the shot, there was enough cloud/sun movement to change the shadows.
So what do you think? Can you tell which lens is which just by looking at the bokeh (or other rendering characteristics like color)? Sure you can cheat by looking at the EXIF, or you could focus all your attention trying to figure out which one had the wider original shot and was cropped, but that would defeat the whole purpose of the exercise.
EDIT: Also, because I forgot to add it to the poll, feel free to post a response in which you state which bokeh you like better, A or B, and if you want, why (preferably before reading the answer).
(Hint: If you want a reference to what the bokeh on each looks like, see my original thread:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/226388-quick-b...1-limited.html)
Lens A:
Lens B:
Last edited by Cannikin; 06-17-2013 at 05:28 AM.