The Six AI Servo AF Cases
Chose different Cases to enhance the AI Servo Mode for different shooting situations and different types of moving subjects.
Each case consists of three variables; Tracking Sensitivity, Acceleration/Deceleration Tracking and AF Point Switching.
- Tracking Sensitivity deals with what the AF sensor does when it’s tracking and then “sees” another, new subject.
- Accel./Decel. Tracking deals with the speed and character of the movement of the subject, is the subject moving steadily or is the subject stopping and starting.
- AF Point Switching deals with how quickly we want the camera to move to the next AF Point.
Case 1 -- This is the default multi-purpose setting if you don’t want to change anything. This works well for steady continuous speed and movement. It’s also the recommended starting place for people starting to shoot moving or action subjects. Try this first, then move on to the other Cases. All three variables are set to the “0” or neutral position of their scale or parameter.
Case 2 -- Chose this if you want to track a subject while ignoring possible obstacles. If the bird flies behind a tree, keep tracking and then when the bird reappears you should still be on it. This is also helpful if you lose the subject when trying to track it. Tracking Sensitivity is set to -1, so by decreasing the Tracking Sensitivity the camera should remain on target. Accel./Decel. is set to “0” and so is AF Point Switching. If the subject is hidden for longer interval consider changing the Tracking Sensitivity parameter to -2. (This is how I set up my camera -2, 0, 0). I used this recently in San Diego for birds-in-flight and it works wonderfully. See how to change this below.)
Case 3 – This case will instantly focus on subjects suddenly entering the AF Points. If might work well for a cycling race when the action shot requires switching from one rider to another, but I don’t think it works very well for bird photography. Tracking Sensitivity is set to +1, Accel./Decel. is set to +1 and AF Point Switching is set to “0”. Canon literature on this Case says “When set to Case 3, if the subject moves away form the AF points, the camera will usually quickly refocus on a different subject or background … So, most birds fly away from us, and then the camera will focus on the background? I don’t think many bird photographers will be using this Case.
Case 4 -- This Case is for accelerating or decelerating subjects. Tracking Sensitivity is set to neutral “0”, Accel./Decel. is set to +1 and AF Point Switching is set to “0” as well. The camera will respond to changes in speed, including sudden stops and acceleration.
Case 5 – This Case helps with erratic subjects moving in any direction, especially side-to-side. The Tracking Sensitivity is set to neutral “0”, Accel./Decel. is set to neutral and AF Point Switching is set to +1, this modifies the speed in which the AF Points change, so they acquire fast erratic moving subjects. Use AF Point Expansion or Zone AF with this, and I think it will work well for Swallows and other quick small birds.
Case 6 – Chose Case 6 for subjects that change speed and move erratically. This is like Case 5 except the Accel./Decel. is +1 instead of neutral at “0”. Again this might work very well for Swallows and fast moving birds.
How to modify the Cases
Go to the AF Menu, and select the first sub-menu. The Quick Control Dial can be used to move between Cases. I scrolled down to Case 2, pressed the Rate Button on the left side of the LCD screen, selected the Tracking Sensitivity Parameter with the Quick Control Dial then pressed the Set Button and with the Dial moved the sensitivity to -2. Then press Set again to finish making the selection and save it.
Which Case you use or what modifications you make may very well depend on your shooting style. Start with Case 1 to see if that works for you if that doesn't then proceed to how I set up Case 2 with the change to the Tracking Sensitivity to -2. If that doesn't work, try changing Case 3 to Tracking Sensitivity -2, Accel./Decel. to +1 and AF Point Switching to +1. Then if that doesn't work try -2, +2, +2 and see if that works for you. There will be some trial and error to this process. Everyone is different and how we each use our equipment is different.
So, I'm using Case 1 as the default, Case 2 with the modification of the Tracking Sensitivity to -2 for my default flight settings, and Cases 5 and 6 for Swallows and other fast moving birds.