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View Poll Results: Which lens is which?
Lens A: FA 31mm Limited, Lens B: Sigma 35mm f/1.4 8072.73%
Lens A: Sigma 35mm f/1.4, Lens B: FA 31mm Limited 3027.27%
Voters: 110. You may not vote on this poll

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06-16-2013, 11:56 PM - 1 Like   #1
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Bokeh Blind Comparison: FA 31 vs Sigma 35

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.
06-17-2013, 12:12 AM   #2
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See attached text file for correct answer. Please don't cheat and read it before voting in the poll.
Attached Files
File Type: txt Answer.txt (49 Bytes, 556 views)
06-17-2013, 12:28 AM   #3
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pretty obvious to me.. LoL!
06-17-2013, 12:30 AM   #4
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Crap, forgot to add to the poll: Which bokeh do you like better, A or B, regardless of which lens it is?

Feel free to post a response with your opinion (use A or B, don't post the lens name if you know the answer).

06-17-2013, 12:31 AM   #5
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Nice comparison. I would have been disappointed if I had been wrong as one is clearly better than the other.
06-17-2013, 12:34 AM   #6
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didnt even need to see B and I knew
06-17-2013, 12:41 AM   #7
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That smooth bokeh gave the answer away!
06-17-2013, 12:42 AM   #8
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I'm not well adept at judging bokeh, so my question is serious. Besides the lighting differences the OP said (which is why I'm ignoring the dark leaves in B), the only difference I really notice is more contrast and saturation in the bokeh the first photo, why is it so obvious that A is one of them?

06-17-2013, 12:45 AM - 1 Like   #9
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QuoteOriginally posted by Codazzle Quote
I'm not well adept at judging bokeh, so my question is serious. Besides the lighting differences the OP said (which is why I'm ignoring the dark leaves in B), the only difference I really notice is more contrast and saturation in the bokeh the first photo, why is it so obvious that A is one of them?
Try looking at the building's windows and columns. The first one will make your eyes linger around. The second one makes one a little dizzy.
06-17-2013, 01:03 AM   #10
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Btw, if you're curious, this is what the building looks like in focus (taken a few minutes later for a sharpness test). Notably, the only green portion is the roof, so the green you see in the bokeh photos in the windows (which are grayish) and lines of the building is merely a result of longitudinal CA.


Last edited by Cannikin; 06-17-2013 at 01:08 AM.
06-17-2013, 01:10 AM   #11
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I also thought it was pretty obvious, so I'm glad I was right!
06-17-2013, 01:13 AM   #12
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QuoteOriginally posted by Cannikin Quote
Btw, if you're curious, this is what the building looks like in focus (taken a few minutes later for a sharpness test). Notably, the only green portion is the roof, so the green you see in the bokeh photos in the windows (which are grayish) and lines of the building is merely a result of longitudinal CA.
Which gives you the answer straight. Really.
06-17-2013, 01:45 AM   #13
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QuoteOriginally posted by drypenn Quote
Try looking at the building's windows and columns. The first one will make your eyes linger around. The second one makes one a little dizzy.
Very good description!

I was surprised how easy it was to tell them apart here.
06-17-2013, 04:08 AM   #14
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I over-thought it and guessed wrong. My stummick screamed that the first one was super-smooth and obviously was the Pentax but my brain over-thought it and didn't see any onions in the second one.
06-17-2013, 04:17 AM   #15
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Thanks a lot for the comparison.

I voted before I even saw that the answer is available. I got it right and was pretty confident but I'm still impressed by the FA 31mm which competes wide open against a stopped down lens.

In some way the lenses aren't worlds apart when looking at details, but even though the difference could be regarded as subtle, I feel the impact on the "feel" of the image is significant.
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