These were all shot with MF and MLU. I converted from CR2 to TIFF in Bibble 5 (ACDSee wasn't saving files it reported it saved), and made JPEGs in Elements 5. Sharpness was set to 2 in the camera, and I didn't sharpen them in either piece of software. The only adjustment I made was to resize in Elements, then set mode to 8-bit and save.
The field of view is slightly different; the tripod was stationary.
I'd be reluctant to buy the sigma because of previous concerns with AF at very near or very far distances, but damn, it sure performs well and it's tempting me to sell the 85L Ii
The out of focus highlights on the 85L gets very distorted towards the edges of the frame, particularly at the larger apertures. The Sigma retains the circular shape much better.
At the smaller apertures, the Sigma is clearly benefiting from circular aperture blades. The 85L highlights look more octagonal in comparison.
In fairness to the 85L, the rendition of out of focus highlights is just a very small aspect of bokeh quality. Color fringing in blown-out highlights and high contrast, busy backgrounds can do awful things to bokeh quality. And it remains to be seen how well the Sigma will hold up in those situations.
I see that at the same f/stop the Sigma blur circles are smaller, indicating the Sigma aperture is either a bit smaller than we think, or just the nature of the designs being very different, the Canon defocuses slightly more quickly outside the DOF zone. Apart from that the Sigma blur circles are very nice and seem a tad smoother or more circular than the 85L circles.
I think the evidence is mounting up that for $900 the Sigma is a great lens and viable alternative to the 85L with at worst 95%+ of the IQ of the L.
Pixel Perfect wrote:
I think the evidence is mounting up that for $900 the Sigma is a great lens and viable alternative to the 85L with at worst 95%+ of the IQ of the L.
Cheers.
Your sentence there is likely to sum it all up perfectly, and I think it's the most we could have really hoped for. In a few months I'll pick one up used for ~$700 and be happy as a clam.
Pixel Perfect wrote:
I see that at the same f/stop the Sigma blur circles are smaller, indicating the Sigma aperture is either a bit smaller than we think, or just the nature of the designs being very different, the Canon defocuses slightly more quickly outside the DOF zone.
If this really indicates that the Sigma aperture is smaller, and I think it does, it matches the other test where the Sigma was darker at similar apertures with equal shutter speed.
Wide open, in relation to the 85L that is really an 85 f/1.256 (thanks theSuede), it seems that the Sigma is something like an 82 f/1.55.
Not necessarily... It explains why the Sigma has a lot less falloff vignetting and no edge clipping of the bokeh circles - it has a different pupil magnification, its' exit pupil is further from the image plane. This is not necessarily linked to the size of the front pupil; which decides the F/no and light gathering efficiency. You can do this quite easily by building a positive Galilaean system after/into the main lens' rear geometry. You wait until the beam-packet has tapered off to a smaller point, and then spread them back out again towards the sensor. If your base is a planar/Xenotar, then you need at least 9 lens elements to keep symmetry though. A very small cost compared to the large, and expensive front elements.
I actually think Canon knowingly sacrificed some vignette/bokeh symmetry/CA correction to gain what is the trademark of the 85/1.2L - the very steep falloff from sharpness to 'blurredness'. You get this by increasing pupil magnification ratio, but you loose out on the points I mentioned earlier.
EXIF data on those samples indicate that all the Sigma photos were taken with 1/3 stop longer shutter speeds than their Canon counterparts. Inspite of this, the Sigma samples still look like they're about 1/6 stop darker than the 85L samples. By my guesstimate, the Sigma is exposing about 1/3 to 1/2 stop darker than you'd expect.
This is consistent with what has been discussed before: the lens isn't quite as bright as it should be. So not everything is sunshine and roses for the Sigma 85mm f/1.4.
theSuede wrote:
Not necessarily... It explains why the Sigma has a lot less falloff vignetting and no edge clipping of the bokeh circles - it has a different pupil magnification, its' exit pupil is further from the image plane. This is not necessarily linked to the size of the front pupil; which decides the F/no and light gathering efficiency. You can do this quite easily by building a positive Galilaean system after/into the main lens' rear geometry. You wait until the beam-packet has tapered off to a smaller point, and then spread them back out again towards the sensor. If your base is a planar/Xenotar, then you need at least 9 lens elements to keep symmetry though. A very small cost compared to the large, and expensive front elements.
I actually think Canon knowingly sacrificed some vignette/bokeh symmetry/CA correction to gain what is the trademark of the 85/1.2L - the very steep falloff from sharpness to 'blurredness'. You get this by increasing pupil magnification ratio, but you loose out on the points I mentioned earlier....Show more →
It is great to learn something new here!
Question:
If the pupil magnification affects the diameter of the OOF highlight disc like it does here, will it not also affect the amount of background blur and hence our sense of subject isolation in the same way as a smaller entrance pupil does?
My issue with Sigma has always been focus speed & accuracy (accuracy being more of an issue if I'm honest). If I could get hold of one to try it, I might be interested, but without really really trying it out in anger at a wedding I wouldn't be comfortable...
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! Terrific!