Auto focus niggle

[MeadsMan]

Hi All,I use a Canon 400D with the Canon 400mm f5.6 prime.It explains in my 400D`s manual,that the camera will focus on what ever is the nearest point,this can be a problem I have noticed particularly with birds,as we more or less always strive to get the Eye sharp,I find my 400D often gets the breast pin sharp,and leaves the eye a little soft.I realise Manual focus is an option,and I do use it frequently,but on small or moving targets,and our normal less than ideal lighting auto focus helps.Can anyone offer any tips to get better more constant results from using auto focus ?

[camo]

Hi Meads Man

Just select the centre focusing spot, then use this spot to focus on the eye, hold your finger down to fix the focus and then reposition the frame for best picture before clicking.

Roy

[glsammy]

All you need to do is get the part you want in focus covered by the centre focus point, half press the shutter. This locks the focus. Then re-compose the shot and fully press the shutter.
If your shooting in AV, program, TV or manual another method is to change the focus point from the centre to any of the others by using dial wheel.

[MeadsMan]

Thanks,I normally leave mine in AF servo,so your saying switch to one shot mode,and use the centre focus point,then recompose ? I will try that method for a while and see how it goes.

Cheers.

[Geoff F]

You can still use AI servo. Just make sure that the camera is set up so that only the centre auto focus point is active. Check centre focus point setting in you camera manual. (You can set any of the multiple focus points as the default point).

I sometimes miss a few shots because I can't get the centre point focused on a moving target in time. But I reject more images when using multiple focus points and the camera has auto focused on the closest point not the area which I had intended to be in focus. Sometimes multiple focus points will focus on the sharper background or the 'wrong' bird in a flock.

The problem will doing the 'shutter dance' (hold and recompose) is that, depending on the selected camera mode, the exposure will reset itself for the new recomposed area. The only real answer is to use manual shutter speed and aperture settings or use the Exposure Lock button. Both of which are fiddly when trying to get a quick shot of a flying bird.

Alternatively, and the method which I prefer, is to pan with a flying bird and stay with it while I press the shutter.

My normal settings are Single Focus Point and One Shot mode for static subjects or Single Focus Point and AI servo for moving objects like flying birds. Also, I normally use Av priority for static shots and Tv for moving targets.

[DaiTheDragon]

A lot of people who photograph birds or sports such as football will change the focusing from the shutter button to the star button on the back of the camera. You will find how to do it on page 101 in your manual. or here it is for you.
Custom Function-4

3: AE/AF, no AE lock
This is useful for moving subjects which keep moving and stopping repeatedly.
In the AI Servo AF mode, you can press the * (star button) to start or stop the AI Servo AF operation. The exposure is set at the moment the picture is taken(when you fully depress the shutter button). Thus the focusing and exposure will always be at the optimum point as you wait for the decisive moment.

I have been using this method for a couple of years. The main advantage is when you start autofocus using the star button it doesn't set the exposure until you press the shutter button.
It's difficult for me to explain it all but you can google it to get mote info. It takes a bit of getting used to but I could never go back to using the shutter button to focus.

Dai

[MeadsMan]

Thank you for the replies,some new methods worth investigating.

[Nick Smith]

can you post some examples? I use a 40D and can refer you to all of the above replies, if you are trying to focus on the eye and then recompossing to get the bird centre shot it is one shot focus mode using spot focus, AF is the way to go if you don't have time to mess about with focusing, if you do have time you are lucky the other option is using a smaller aperture to get more DOF which increases your chance of getting the chest and eye in focus of course then you are really relying on good light to keep your shutter speed up. tbh from your thread title i would hazard a guess you are using AI servo which will be re-adjusting your focus constantly.



I am no expert of course,

[MeadsMan]

That was my point,the camera will focus on the closest point,and re adjust focus if you change the composition,I think one shot is worth trying,with just the centre focus point selected,then just hope the bird dosn`t move out of foucus again in the time it takes to re compose,once you have the eye in focus.I agree some good light always helps, so we can stop the lens down a bit too.

[Markulous]

I use the seperate * button setup - if I use AF then focus (using "better" central focus point) and recompose. Sometimes I'll AF roughly then finalise with MF but often the subject's moving too fast/erratically and I resort to MF!