Focusing Issues with Canon 5D M3

[Marina S]

Hi Brian,

I have been experiencing some focusing issues with my gear lately. I shoot with Canon 5DM3. These examples were shot with different lenses 24-70mm and 70-200mm. I use back button focus and I have calibrated all of my lenses to my camera. My gear had its last service a few months ago. The focus falls somewhere else rather than where I want it so often I just don't know what to do anymore. I have a plug in for LR that shows where the focus point fell and in both images its supposedly right on the face/eyes yet the photo of the child has the hands in focus and the photo of the woman is not in focus at all.  Is it the camera, the lens, calibration? I have so many sessions coming up I wonder if I should buy a new camera body until I have this problem figured out. I need back up anyway...

 

[Brian]

OK, first off...

Back-Button Focus is not the end-all-and-be-all that it's made to be. It's an easy blog post. It's not a "Secret Technique" that will take you to the "Next Level." I know, I know..."It worked so well for me?!! It's what solved my problem!! I'm such and #amazeballz photographer now and my clients #lovelovelove my photos!!!! Ummm, yeah. I say it's a technique like any other; it works for some and not for others. BBF is relative. So as a test, turn focusing with the shutter button and see if your focus improves. I also need to know what focusing mode that you were using.

Second, calibrating your lenses usually works, but it's really hit or miss. If you really want your lenses / body to be calibrated, it's better for Canon to do it. I'd set everything back to "zero" or default for the short term. Let's get away will all the "stuff" I'm sure you have picked up along the away. From what I can tell, your camera / lenses are front focusing on all four sample photos. It's on the belly and seems to be along the ridges / forheead, even the floor in front of the kid.

Third, the original Canon 24-70 has all sorts of focusing issues. It's usually crap wide open or zoomed in at 70mm. I know several photographers in real life that can not trust their Canon 24-70 on a gig. The have a hate-relationship with that lens. I also know of a camera store in NJ that used to make people take home a Canon 24-70 for a weekend before buying it. Why? Because they got tired of the returns for soft-focusing or front-focusing. The solution? Buy a Canon 24-70 f/2.8 L Version II lens. That lens is the "fixed" 24-70. Now before people start *GASP* -ing, if you got a good copy of the original Canon 24-70 f/2.8L, you'll love the lens. I've seen incredible photos come out of good copies. But that camera store I was talking about? 4 out of 5 lenses had focus issues. It's that bad. It just sucks that you have to fork out around $2000 for the "fix."

Fourth, not all focus points are treated the same. The strongest focus points are what's known as "Cross-Type," which means they take phasing info from two axis (X and Y) to determine focus.

"Huh?"

Phasing Is how a camera focuses. For an easy demonstration, put one hand over the other with your fingers spread. Line up all the fingers so that the gaps between the fingers are consistent. That's in focus or "in-phase." Now take one of your hands and turn it slightly counter-clockwise. The fingers in one of the hand occupy the space/gaps between the fingers of the other hand. That's out of "Phase" or out of focus. Understand?

Within the 5D Mark III, there are certain focus points that are better than others. As I've stated above, they are "Cross Type." As a bonus, there are some that are known as a "Double Cross-Type." These are the most accurate focus points in the camera. The standard cross-type focus points are good, and the regular focus points are ok, especially if there is enough contrast-swing. So we have a Good-Better-Best scenario. I swiped this image from the internet so you can see what I'm talking about:

The Focus points that are blue with the X are the strongest out of all of them. The orange ones are the standard cross type, which work pretty well, and the ones in white are the "Meh" focus points. Which one do you seem to pick the most when you have your issues?

Oh, one more thing, the camera needs enough contrast swing in order to determine focus. So if you put the AF point on the eye and are like 20 feet away, the focus point is picking up a pink-blob and not the dark area of the eye-lids. Your human eye is way better than any camera sensor. So your brain knows what it wants and tells your eyes to focus. That maternity shot, even though you put it on her face, her Caucasian skin and blonde hair made the camera confused. The blue dress and her hand had a much better contrast swing. It took me a few blown photos to get it through my thick skull that putting the AF point on the eye may not lead to in-focus photos. The solution? Pick another area and stop down and have your subject further away from the background. f/4 is way more forgiving than f/2.8. Heck, f/3.2 is more forgiving.

Finally, I shoot Nikon. There are 3 different modes that you can set on my camera, one is *I* pick the AF point and the camera doesn't argue, the other is I pick the point and if the camera thinks it has a better one, it will override me, and finally...the third mode is the camera picks the AF point, with no input from me. I call this the dummy focus mode. So let's get back to basics, figure out how your camera is setup or change things back to the defaults.

Oh, you want either One Shot AF for steady subjects and AI Servo for moving subjects.
 

[Brian]

I had one more thought. Did you ever turn off focusing via the Shutter Button when you switched to BBF? The reason that I ask, is if you BBF and recompose, if the shutter button is still set to engage the focusing system, you'll get weird results. I know, dumb question, but I have to ask.