40D- Autofocus not that good thus far?

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Graelwyn

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Bit disappointed. Set up my new 40D, stuck on the 28-135 USM IS lens and went out to test it out. Sun was going down but it wasn't dark. It just seemed to struggle to lock focus on anything. Not sure what the issue is...
 
what were you trying to focus on? AF works by detecting the difference in contrast between items, so if you were trying to lock onto something all one colour (say a blue wall, for example) it'll struggle because there's no difference in contrast for it to lock on to.

Can you show an example of something that it wouldn't focus on?
 
Eh shall try. But I tried several different scenes including boats in water and an old church tower and it couldn't decide if it was finished focussing or not.
 
mav said:
wer you using one shot or a1 servo one shot will beep when focused
Click to expand...

unless you have turned the annoying beep off, but yeah if you have it on AI servo mode (changed by pressing the AF.Drive button and turning the smaller wheel by the shutter release) it might be hunting and the red focus confirmation lights might not shot. Shove it into "One Shot" and see if it helps. As far as I understand the auto focus is controlled by the lens not the camera - but I could be wrong.
 
Would be worth selecting just the middle AF point too.
 
Graelwyn said:
Bit disappointed. Set up my new 40D, stuck on the 28-135 USM IS lens and went out to test it out. Sun was going down but it wasn't dark. It just seemed to struggle to lock focus on anything. Not sure what the issue is...
Click to expand...

As noted above you need some contrast to have AF work well however, even with some slight contrast, the slow lens may not let enough light in for AF to work as well as it can.

Get a faster lens and you'll see a big difference.
 
Graelwyn said:
Eh shall try. But I tried several different scenes including boats in water and an old church tower and it couldn't decide if it was finished focussing or not.
Click to expand...

Did you select just one AF point?
 
CT said:
Did you select just one AF point?
Click to expand...


I have absolutely no idea... ? I just set a few basics, put it on both programme and manual (as without the flash it seemed incapable of getting a shot indoors) and had it set to A1 servo. No idea what focussing points it used or how I would deal with that?

Either way, it took ages to auto focus.
 
Servo AF works but minutely moving all the time to see if it can improve the focus of what it's currently locked on to. It can cause focus errors on static objects if you're not careful.

Single AF and one AF point selected is the best for normal usage really
 
LOL. OK a few points.

Servo focus focuses continually as long as you maintain that half pressed position on the shutter button and will continually be making slight adjustments just for your own body movements as well as subject movement- if applicable. I can see why you'd think it hadn't finished focusing, but the fact is it's focusing all the time and I find it pretty accurate. The other thing with Servo AF is that you don't get that green focus confirmation light in the viewfinder as you do with 'One Shot' AF.

To select an AF point(s) press the far right button on the back of the camera with your thumb, which lights up the active AF point(s) then using the front scroll wheel ( just behind the shutter button) you scroll around the AF points and select any one or all of them. You may not be able to do this in some modes, but you certainly will in Manual, AV and TV

There's nothing wrong with your shots and nothing wrong with sharpening in processing either - remember no sharpening is applied in camera to RAW images. They do look a mite over-sharpened but it's early days. ;)
 
These images are well over size btw Graelwyn, so please resize them or just remove the img tags if you prefer.
 
on top of the camera press the af/ drive button

scroll the wheel to one shot

make sure beep is enabled in the menus
this will give you one shot af
and a beep when it is locked on

the portrait picture is pin sharp
so nothing wrong with the camera
i would guess
 
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