Monday, August 13, 2012

Ask Ron: Does the 5D Mark III make autofocusing faster with traditionally slow focusing lenses?

Keeping up with a toddler is tough enough, slow AF lenses take that challenge to a whole new level. My hit rate was about 1 out of every 20 for this fast little dude
5D Mark III with Canon 85mm f/1.2L – 1/125sec @ f/2 ISO 400 (flash fired)

A reader writes:

I’ve heard that the autofocus system in the Canon 5D Mark III is so good that even traditionally slow focusing lenses work much better than in the past. Is that true?

I’ll cut to the chase and say, not really. In my real world testing I found that two of my favorite, but also most frustrating lenses (which I’ve bought and sold twice) performed just as bad as they always have with cameras from the past. This is a subjective test, not scientific one, so some may choose to argue with me. However, I didn’t find myself saying “wow, look at all of these perfectly focused shots I’m getting”. Instead, I was typically saying “f#@k” as shot after shot would often be out of focus.

Even when you do everything right and hit your target, these lenses can still disappoint
85mm f/1.2L at f/1.2 for 1/125 sec at ISO 400 (flash fired)
Focus was aimed at the right eye but I hit the eyebrow due to the shallow DOF of f/1.2

Remember, a f/1.2 lens is going to have a shallow depth of field
which is a challenge even if the camera nails the focus
50mm f/1.2L at f/4 for 1/125 sec ISO 1250 (flash fired)

Now I’ll add the disclaimer that at f/1.2, it doesn’t matter what lens you are using or how fast it is or the camera its attached to. f/1.2 is shallow so moving subjects are going to cause misses unless you track subjects like a sniper. I tried to discount those “user error” misses from my testing and just pay attention to my keeper rate when doing typical shooting (sometimes as high as f/4 or f/5.6).

Out of 40 shots, only a handful acquired the focus quickly enough for the moving subject
Most often the camera would hunt for focus so long that the shot was gone
50mm f/1.2L at f/4 for 1/125 sec at ISO 1250 (flash fired)

Ultra-low light, kids and these lenses? Fugetaboutit! I was aiming for the eye and got the ear
as the camera was hunting for a while with this lens to get any focus at all
50mm f/1.2L at f/4 for 1/125 sec and ISO 1250 (flash fired)

Keep in mind that it’s in my best interest to tell you that these lenses do focus faster as your buying them from links in this blog helps support what I do. However, I’m here to tell you the truth as I see it, and I say that these great pieces of glass still focus like crap with current cameras like the 5D Mark III. Hopefully we’ll get new versions in the future that address this problem.

I should also note that I don’t expect that this is isolated to just these two lenses. Great lenses like the 135mm f/2 are probably just as slow too.

The Test Lenses

The Canon 50mm f/1.2L and 85mm f/1.2L (available for rent by are legendary for their wonderful bokeh and excellent sharpness. They are indeed magical lenses, but for those who have plunked down the $1500 – $2000 for these two lenses, you’ve quickly found out that it’s easier to get an out of focus shot than it is to get one of those magical shots. Some say that the big heavy glass is hard for the little AF motor to move, and others cite the longer minimum focus distance. However, the real reason doesn’t matter – the fact is that these are very tough lenses to use if you are taking photos of anything that moves as they are glacially slow to acquire a focus and often will hit the wrong spot or not track very well. As a result, these are lenses that you do have to spray and pray a little bit with as everyone I’ve known (including some very well known pros) has said that no matter what camera you have, you’ll have more misses than hits.

When you nail a shot with these lenses it’s still magical, so I’m not saying don’t buy these lenses – I’m just saying set your expectations properly and plan to be deleting more than you keep with these lenses – even if you have a fancy new camera. Personally, slow focusing lenses these will stay on my “rent as needed” list rather than my buy list.

Given the legendary status of these lenses and the fact that they are generally a pain in the ass to use, I thought they’d be great candidates to use to answer this question.

For the record, the 50mm f/1.2L performed SIGNIFICANTLY better than the glacially slow 85mm f/1.2L.

How I Tested

I followed my family members (mostly my toddler) around in low light situations and attempted to grab some candid shots. I typically used the spot auto focus feature (new for the 5D Mark III & 1D X) as I find that it has laser pointer focus with other lenses. However, I tried all of the different focus types when I was getting a high fail rate just to ensure that I wasn’t hitting a limitation of the focus mode I was using.

I tried with both AI Servo for moving subjects and One Shot for stationary subjects. Generally speaking, AI Servo failed really bad with these lenses.

Since I was using a flash, the 1/125 sec shutter wasn’t typically an issue as the flash would freeze movement. If I was shooting without a flash, I would have shot many of these at 1/500 sec or faster.

What about the 1D X?

From what I saw during my real world testing, my 1D X offered no measurable improvements over the 5D Mark III in this particular test with these two lenses. I’ve noticed improvements in its AF system overall with super fast AF lenses like the 70-200mm, but the slow focusing lenses are still cumbersome with the 1D X as well from what I’ve seen.

Special Offer

This article was brought to you by They generously donated a free rental of the 50mm f/1.2L and 85mm f/1.2L for the weekend so that I could experiment with them to answer this question. has been gracious enough to offer you a 5% discount off any order when you enter the coupon code MART5 as shown below in yellow: Coupon Code

Where to Buy?

Click here to buy the 50mm f/1.2L from B&H, or click here to buy it from Adorama.
Click here to buy the 85mm f/1.2L from Adorama, or click here to buy it from B&H.


If you make a rental or purchase using select links in this article, I may make a commission. See the special offer for more disclosure details.

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Phototoasty said...

Hey Ron, I beg to differ!

Yes my 85mm f/1.2L II would often disappoint when used on my Canon 5D II especially at f/1.2. From anything more than "Portrait distance" the 5D II would rarely nail focus at f/1.2, even on a static subject let alone a moving one. However, I have found the focussing of this lens with the 5D III to be absolutely excellent. Using your tip to toggle between one-shot and AI-Servo I have managed to get some great action shots of the kids. I have some great results even at f/1.2 but stopping the lens down a little to f/2 helps.

For example, take a look at these shots on my Flickr stream.

I have uploaded at full resolution so that your readers can see how sharp they are.

I can now use my 85mm f/1.2L II with confidence!

The same goes for my 24 f/1.4L II.

Chris said...

Hi Chris,

Thanks for chiming in.

I can see how you'd see a significant improvement by taking advantage of the AI Servo/One Shot toggle, and by looking at your images and seeing your comment about "anything more than portrait distance" implies that you are probably doing more longer distance movement shots with these lenses. That's a place where AI Servo improvements do indeed matter, so I can see how you observe there is an improvement.

What I was mostly testing was the One Shot AF scenarios and the time it takes to actually aquire focus. As a user of a 1D Mark IV, I already had a camera that did well with AI Servo scenarios with these lenses but focus acquistion time and accuracy in One Shot was abysmal no matter what camera I used. I have not observed any benefit in that area with the lenses tested using the 5D Mark III, so I stick to my comment.

I would agree with your comment and your photos though that AI Servo improvements are signifcantly better with all lenses on the 5D Mark III over the 5D Mark II simply because the old version on the II did in fact suck quite bad. The NEW 5D Mark III AI Servo improvements put it on par with my 1D X in most aspects, so there should be a night and day difference there. Thanks for raising that point as I probably wasn't clear enough in my article on this detail.