Canon 85mm Lens Comparison EF 85 1.8 vs 85 1.2 L 

PART ONE

Portrait and glamour photographers who use full frame cameras love 85mm lenses for two main reasons:

First, this focal length helps keep a person's facial features in proportion.  Shorter focal lengths can make the nose look too large.  (Longer focal lengths require you to back away from the model, so they are harder to use indoors and can make it difficult to communicate with the model.)

Second, 85mm lenses are great at creating smooth background blur called "bokeh" that helps to separate the model from the distracting background.  Photographers love to talk about which portrait lens creates the best bokeh.  

The king of bokeh-producing portrait lenses is the Canon EF 85mm F/1.2 L, which sells for around two thousand dollars.  You can check the latest price here if you wish:  Canon Price Watch is a great place to keep track of current prices.

Canon also makes the EF 85mm F/1.8, which is about one fourth the cost of the "king."  It also weighs much less, 425 grams compared to it's big brother's 1,025 grams!   I've been using this lens for a few years with good results, but I've read so much about the 1.2 L that I had to try it out.  Fortunately, there are good places to rent lenses.  My favorite is LensRentals.com, where Roger Cicala has an interesting comment about this lens.

The lens arrived by FedEx on schedule, with a return shipping label included in the price.  I had one week to try it out in my style of shooting and decide if it was worth two grand to me.

Here are the two lenses side by side.  The first thing you notice about the 1.2 L is the odd shape, the second thing you notice is the massive weight.  It feels like it is made of cast iron, because it weighs over two pounds.

side by side

85L on camera

EF 85 on camera

The first thing I do when I get my hands on a new lens, especially a large aperture prime lens, is test the focus accuracy.  If necessary, I will use the Autofocus Micro Adjust feature on my camera to correct any front or back focus error.  The method I use for this is primitive, but effective.  The camera/lens combo is placed on a tripod, angled down toward a large cardboard chart that looks like graph paper.  A simple piece of black tape makes a good focus target and the graph lines allow me to easily find the actual point of focus.  

I like to test at roughly the distance that I expect to use the lens, since some lenses are known to have differing focus errors at different distances.  In this case, the camera is ten feet from the target.   Each one of the little squares is one inch, which will give you an idea of the depth of field.  Ignore the differences in brightness and color, they are not caused by the lenses.

I've used this grid chart to test at least a dozen lenses, so please allow me to add some comments based on my experience.

Neither of these lenses is built for absolute sharpness.  They both have very visible chromatic aberration at wide apertures.  You can see the obvious purple fringing just in front of the black target and mild green just behind it, especially in the wide open shots.  They both lose some contrast and sharpness wide open.  They both focus very accurately under these conditions.  The 1.2 is using +1 AFMA and the 1.8 is using zero.  

I don't see much difference in focus accuracy or sharpness.  These are both great portrait lenses, which is my sole criteria for comparison.  I did not check for vignetting, because I generally add a lot of that in post processing to get the look I want.

The most important thing to point out for most readers is the extremely shallow depth of field.  Shooting at ten feet at F/1.2, there is roughly a three inch zone of sharp focus.  Yes, that's why we use these lenses, but making it work for your style of photography can be difficult.  It's a good thing they both autofocus accurately, if they didn't it would be a nightmare.  And remember that your camera body is a big part of autofocus accuracy.  Not all cameras focus as well as the 5D III.

The 1.2 is known to have a slow moving autofocus motor.   If you aren't shooting sports, it probably isn't an issue.  The only time I was bothered was when I tried to go from near the minimum focusing distance to infinity, not something I do very often. 

With the focus calibration finished, it's time to shoot some real photos.  On to part two, which is Not Safe For Work!