Sigma 85 f/1.4 and 135 f/2 L, which blurs the background more for portrait?

suppose both wide open, the subject has the same FOV (or the same size in the picture without crop), which one has more blur in the background?

DOF

I THINK that the 135mm should have more blur. I've seen somewhere that you can find it out by comparing aperture sizes, but i could be totally wrong...

I don't have any numbers for you.. But from experience, they're very close, almost identical.

The 85mm @ f/1.4 would yield slightly more blur.

Example:
135mm lens @ f/2 standing 20 feet from the subject will render a point 10 feet beyond the subject as a blur disk with a diameter of 0.50mm on the sensor.

85mm lens @ f/1.4 standing 12.6 feet from the subject will render a point 10 feet beyond the subject as a blur disk with a diameter of 0.59mm on the sensor.

This shows the scenario requested, with the size of the blur disk / the CoC as the parameter of interest. Quite frankly, I'd use whichever focal length is best for working distance as this is so close as to be meaningless.

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tomme wrote in post #12282450
DOF

Thanks!

I understand that f/1.4 will have less DOF than f/2, but DOF isn't the same thing as the amount of blur

actually i just find this , not siggy 85 vs 135 f/2, but
nikon 85mm f/1.4 vs nikon 135mm f/2 DC, good reference nontheless

http://beingelvish.mul​tiply.com/reviews/item​/9

JeffreyG wrote in post #12282460
The 85mm @ f/1.4 would yield slightly more blur.

Example:
135mm lens @ f/2 standing 20 feet from the subject will render a point 10 feet beyond the subject as a blur disk with a diameter of 0.50mm on the sensor.

85mm lens @ f/1.4 standing 12.6 feet from the subject will render a point 10 feet beyond the subject as a blur disk with a diameter of 0.59mm on the sensor.

This shows the scenario requested, with the size of the blur disk / the CoC as the parameter of interest. Quite frankly, I'd use whichever focal length is best for working distance as this is so close as to be meaningless.

Thanks a lot for the info!

I think I've decided to get the Siggy 85mm f1/4 mainly because
1) It can be used indoor better because of the focal length
2) it works for both my 60D and 5D, while 135 f/2 will be a bit too long on 60D
3) it's better for low light

Thanks to everyone who replied

As far as the Bokeh is concerned I used to shoot both he 85 1.2 and 135 2 when photographing people. I do shoot wide open a lot but tend to like the 85 1.2 on my 1/3 crop MKIII set at 1.6 which is my all around favorite spot for bokeh bit depending on distance to the background I may stop down to 2.5 doing headshots. The 135 2 also blew me away with it's extreme bokeh on the same camera and occasionally it felt like too much and I's stop it down a half stop I don't know about the 85 1.4 you are talkin about, I've never even seen someone using a sigma but read that quit a few here on POTN use them.

tomme wrote in post #12282450
DOF

Unfortunately, dof calculator won't give any information about blur and bokeh
Somebody tried to put two samples at same aperture between sigma and canon ..
https://photography-on-the.net …/showthread.php​?t=1031462
as we can see sigma is rather far from canon for blur softness out of focus ...