7D and front focusing problems

[Art Vandelay]

There's really 2 seperate issues here.

If your getting focus sometimes and not others, it's not a micro adjustment issue. it's an AF issue (either camera or user). A front focusing problem will be there across the board, (with the same lens) it wont pop up every now and then. From that handrail shot, You may have to do that with your 50mm f/1.4 if you test it as descibed earlier up the page.

The surf shots with the 100-400 look and the dance shots with the 50mm are an AF issue as, as you say, some are OK. they're not an MA problem.

Adding to what mark said on the custom function of selecting AF priority, you can also adjust the tracking speed. i.e. how long it holds a point before switching to another. That maybe worth experimenting with, as some of those shots the area of focus is in a different area to where you expected them to be. The point may still be tracking that front wave instead of tripping to the surfer as you moved the camera. I wouldn't totaly rely on the DPP software showing which point was used, I've seen some anomalies in this, it doesn't also show the difference if it's used the main point or an expansion point in those modes).

from the canon site,


C.Fn III -1 – AI Servo tracking sensitivity

This Custom Function has five levels, from slow to fast. The levels are:

0 = Standard sensitivity. AF will momentarily pause if the AF point sees another subject while tracking.
-2 = Slow. Tracking will pause for a longer period when AF is disrupted to allow you to find the original subject with the AF point.
-1 = Moderately slow. Pause length will be between -2 and 0.
+1 = Moderately fast. The AF system will respond faster to a change in subject position.
+2 = Fast. AF system will not pause. If the subject escapes the AF point, the camera will instantly re-focus on the area the AF point is currently covering.
The focus tracking sensitivity refers to how the camera responds and switches to another subject during focus tracking. This response sensitivity refers to how long the camera waits before switching to a new target subject when the current target subject escapes an AF point. It doesn’t adjust how quickly the autofocus tracks. The shorter the response time, the faster it will switch subjects to track a new subject. Therefore, if you want to quickly track changing subjects, set the sensitivity to a faster level.

However, if you want to track the same subject as much as possible without switching to another subject, set this sensitivity to a slower level to force the camera to continue tracking the same subject, even if a distracting subject enters the frame or if the subject is erratic and likely to escape from an AF point.

You should try each of the settings out to find the one that works best for you, but generally, you will find that setting -1 or -2 for fast moving, erratic subjects produces better results.


There's a full explanation of all the custom functions here