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Focusing issue with Canon 90D + EF 70-200mm f/2.8 IS USM



just noticed pretty strange focusing issue while shooting sports (indoor, great lighting) last weekend.

I was trying to focus on the expressions and the faces of players using Zone AF (9 point focus with 90D, AI SERVO) while they were moving but about 90% of pictures came out blurry or the focuspoint was on their feet and below their knees. 

I also took testpictures with Zone AF of stationary coachingteam with 200mm focusing on their faces and the issue recurred again. The focus was at the bottom of the picture. It's pretty much like the focusing points are upside down and it's pretty annoying. I deleted all the settings from the camera and cleaned the contact points from the lens and camera but it didn't work either. It seems the problem occurs when i'm shooting at 200mm with the lens.




If you were using AI Servo, then that may have been the problem.  AF performance can be a bit sluggish as the camera decides to use One Shot mode or AF Servo mode.  During which time your subject may move out of perfect focus.  

Most user never use AI Servo mode.  Use AF Servo for moving subjects.  Some users like to use AF Servo for both moving and still subjects.  The only change they make is to drive mode, One Shot or Continuous Drive Mode.

"The right mouse button is your friend."



Does the same thing happen if you use Single Point as opposed to Zone focusing?

Steve Thomas


The two answers above are the issue but they need to be combined. Next time try One shot and just the center focus point. Here's the deal One shot will not fire unless focus is achieved. Big factor. Ai-servos will fire when you press the shutter button. It doesn't matter if focus is achieved or not, it fires. One last point when you have multiple focus points like 9 for instance the one closest to the camera is usually the one that gets selected. Camera doesn't care if it is a foot or a nose if it is closer.

EOS 1DX and 1D Mk IV and less lenses then before!


Several points but starting with your last because it will impact everything else, you are probably shooting with the lens wide open (f2.8) and that creates a narrow depth of field.  If you haven't done so already, make sure that the lens is calibrated properly to the camera body using Canon's microfocus adjustment procedure.  That is critical with wide aperture sports shots at the telephoto setting.

Otherwise, the proper setup for almost any sport is NOT going to be zone AF.  You need to put the focus point where it needs to be or far too many of your captures will not be focused upon the desired part of the image.  Use single point or single point with expansion and place that in the part of the focus array which is most commonly going to be on the face of the athlete in the sport you are shooting.  Most of the time you will choose a point somewhere in the midpoint of the arrary or up.

AI servo is generally a much better choice than AI focus for shooting sports. 

Three items you need to check in the custom settings are under CFn II-2, -4, and -5.  CFn II-2 deals with tracking of randomly moving subjects which you will have in gymnastics.  You will have to experiment with this configuration for the best setup for your shooting style and any particular parts of the routine you emphasize.  But I would expect this needs to be biased towards subjects that move randomly since you will have a combination of brief pauses combined with sudden action.

CFn II-4 and -5 deal with priority between capture and focus.  I always set the bias towards focus, I don't really see the point in capturing a blurry image.  This bias may cause you to miss some captures but I have no desire to capture an image that isn't razor sharp.  So I would set these two settings (first and second image) to focus priority.

The setup is in the full camera guide, download the pdf for your camera body from the Canon support site if you haven't already.  Microfocus adjustment is also covered by Canon, you can download that from the Canon site also. 

I use a slightly different procedure than Canon calls for.  They instruct you to take a series of photos at a single microfocus offset and then make a different offset based upon whether the camera is front or back focusing.  Instead, I will take three test shots each at 0, +3, +5, +7, -3, -5, and -7 offset and examine them to quickly zero in on the exact offset needed.  The EXIF data will show the offset so you can easily see what was used for a specific image.  I may use the same lens on 7 different camera bodies and using my alternative method, I can dial the lens in for all bodies in 30 minutes or less.


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