Al servo?

[Sam_swfc123]

Hello. Can some one tell me what this Al Servo is? Does it come on every camera such as the Canon EOS 20D? Thank you.

Sam Winslow

[John D]

Hi Sam,
The Al servo mode is for maintaining focus when the subject's focus position keeps changing. In Al hold down the shutter button half way and the subject will be continually focused. Ideal for birds in flight etc.

Hope this helps.

John D
Zenfolio | John's Wild World

[eeyore]

Originally Posted by John D

Hi Sam,
The Al servo mode is for maintaining focus when the subject's focus position keeps changing. In Al hold down the shutter button half way and the subject will be continually focused. Ideal for birds in flight etc.

Hope this helps.

John D
Zenfolio | John's Wild World

what he said

and yes you do get it on the canon 20D - it is also a feature of most new dslrs , though some of them have AI focus instead , which basically means the camera decides whether tracking autofocus is necessary rather than you forcing it - the plus side is this can extend battery life , while the downside is that it does depend on the camera selecting the right subject for the decision

also note that AI servo and AI focus are the canon designations - it is named differently on some other makes

[Geoff F]

There is an article about using the various forms of autofocus here Understanding Camera Autofocus

I find AI Servo is essential for moving subjects. But switch to One Shot for macro work or other static objects.

There is a choice of multiple or single focus points. Personally I prefer to just use the centre spot to prevent my camera from accidentally focusing on the 'wrong subject'. But this does mean that you have to point the lens very precisely, while the multiple point option will lock on to the nearest point.

I also, usually, prefer to use spot metering (or which is the closest to that on a 20D) but if you are unsure about this stick to Evaluative.

Here is a photo of a 'big bird' which I took while looking for wildlife last week.



AI Servo is essential for this type of shot. Sigma 150-500 lens on a 40D. I didn't have much 'thinking time' here so some of the camera settings weren't ideal