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The Canon 50mm f/1.2L is a remarkable lens. I won't go on and on about it since I'm not a lens expert. However, in my unqualified opinion, the 50/1.2L has to be one of the all-time great 50mm lenses in 35mm photography. The knock on the Canon 50L (besides it being somewhat "uncool" to be a Canon in a Canon-dominated world) is that it suffers a noticeable degree of focus shift. That is to say that at close focus distances, the focal plane at higher f-numbers (smaller apertures) is closer than the focal plane at f/1.2. Since the camera focuses each lens at full aperture, the result is that close range images at higher f-numbers end up out of focus (back focused). Apparently this degree of focus shift is the result of uncorrected spherical aberration. I assume the same uncorrected spherical aberration helps explain the excellent job this lens does with rendering out-of-focus background elements. With its modern C-Sonnar T* 1,5/50 ZM (the early version of which HCB used on his Leica M bodies), Zeiss describes focus shift more as a feature than a shortcoming. Click here to see a good demonstration of focus shift from the Sonnar. However, those who complain about the Canon 50mm f/1.2L suggest that Canon ought to have used a floating lens element to correct for near focus performance, just as they did with the 35mm f/1.4L and 85mm f/1.2L.

An alternate solution for the 50L focus shift - that Canon address it with a firmware update - was proposed some time ago by Joe Mama in the DPReview forums. At the time, I thought it was an excellent idea; but I wasn't convinced that it could be done. Lately I've been reading more about older film cameras and came across some interesting information about a relatively inexpensive autofocus film camera, the Konica Hexar AF (http://www.camerapedia.org/wiki/Konica_Hexar). The Hexar had a built-in 35mm f/2 lens that is said by some to have equalled or surpassed the best Leica had to offer at this focal length. Konica decided to leave a fair amount of uncorrected spherical aberration in this lens, which apparently contributed both to sharpness wide open and extremely good handling of bokeh at the expense of significant focus shift (http://wiki.silvergrain.org/wiki/index.php/Konica_Hexar). Their solution for the focus shift was to simply have the on-board computer adjust the AF in an aperture-specific manner.

Adding a floating lens element to correct for near focus would likely add to the cost, and potentially also the size, of the 50L. Seems to me that in this era of autofocus, the software route is even more elegant than the optical fix. Konica did this in 1993. Fifteen years later, I think Joe had it right. Canon should be able to manage this with a firmware update.

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If you're reading this post wondering "What the heck is bokeh?", read this first. Otherwise, run over to RangefinderForum.com and check out "The ultimate Bokeh thread." 16 pages (and counting) of the good, the bad, and the downright freaky.

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Mike Johnston, in his short publication "Lens Bokeh Ratings," states the following generalizations about bokeh (out-of-focus blur):

I’ve found as a general rule that bokeh gets progressively more problematic:
• the larger the aperture
• the closer the focus
• the more distant the background
• the more contrasty the background

I think that when we discuss which lenses produce nice OOF blur (bokeh) compared to those that don't, we too often compare lenses under the worst of circumstances. For example, here are two shots of my sons with the 50/1.4 under nearly the worst of circumstances (Click on image for full size):





From these, one might conclude that the 50/1.4 harshly renders OOF blur (bokeh). This is far from true. Compare the OOF blur from the 50/1.4 at f/2.8-f/4 with any 50mm lens irrespective of price range, and it will compete well. Conversely, take the last generation pre-aspherical 35mm Summicron-M and shoot it wide open with a close subject and a distant, contrasty background. Even the so-called "King of Bokeh" will render a harsh OOF background blur under such circumstances.

Now see how the 50/1.4 renders an extremely challenging background at f/2.8:



Significant improvement. Now take a few moments to consider William Castleman's bokeh comparison of the 50/1.2L and 50/1.4.

An interesting consequence of this effect of stopping down on the quality of bokeh - independent of the quantity of background blur - can be seen in this bokeh comparison between the 35L on the 30D and 50/1.4 on the 5D.

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I just joined a Virb group called BOKEH. What the heck is bokeh? Read on.



Boke (pronounced and spelled alternately as "bokeh") refers to the characteristics of the out-of-focus portion of an image. It refers to the entire blurry area (both foreground and background), not just the round highlights.

John Kennerdell, the author of one of three articles in PHOTO Techniques (PT) that introduced boke to the West, had the following to say on Mike Johnston's blog: "In retrospect, in those articles in PT we should have introduced one more Japanese word: 'pinto' (prononunced 'peen-toe,' not like the beans). It means in-focus. Anything in a photo that isn't pinto is boke. It really is that simple."

It is apparently difficult to design lenses which do a good job handling the in-focus/sharp areas of a photo (pinto) while also nicely rendering the out-of-focus regions (boke). The quality with which a lens draws out-of-focus areas cannot be objectively measured as we do lens characteristics pertaining to in-focus regions (resolution, contrast, etc). Rather, appreciation for boke is inherently subjective. Yet the way a lens renders boke can be just as important as the way it handles pinto. Many people only worry about whether a lens is critically sharp. Differences in sharpness are generally apparent only in large prints. Poorly-drawn boke can ruin a 4x6" or web-sized photo!

Here are some links for further reading about boke:

PA van Walree on "Bokeh"

"Understanding Boke" by Harold M. Merklinger

Rick Denney's "Bokeh Test"

"Bokeh in Pictures" by Mike Johnston

More about boke from Mike Johnston

If you want to eek a little more knowledge about boke from some really long threads, here are three for your perusal:

DPR thread started by joe mama
POTN thread started by booggerg
DPR thread started by TheronFamily

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