Focus behind subject..how can I avoid this (example pic)

[willg]

seems like the camera likes to choose things other than what I want. Focus point was center and wide open (70-200 f/4 at 200)

http://www.spideronthefloor.com/upload/files/bird.jpg

I sent the lens in about 8 months ago because I thought it was backfocusing, came back but I really haven't been happy with it. Is this something that I am doing? The bird was very small on the frame, so maybe my focus points aren't small enough to decide ???

[4x4rock]

Does it do this consistently or with only with certain small subjects? What happen if you focus on something bigger with better contrast? Will it still be back focus?

What focus mode you're on? Unless, you're on AI Servo and the bird is moving fast, there's no reason why it should be that OOF.

[willg]

Does it do this consistently or with only with certain small subjects? What happen if you focus on something bigger with better contrast? Will it still be back focus?

What focus mode you're on? Unless, you're on AI Servo and the bird is moving fast, there's no reason why it should be that OOF.

I believe it was servo, but he wasn't moving too fast. You don't think its because the bird was so small on the frame? That is a 100% crop from a full size 5d image. I will try some more shots with larger subjects, but my warrenty is up in June so I will be sending it in before then if I am not 100% happy

[Billginthekeys]

i really doubt that that much OOF is due to backfousing. probably the lens just miss focused, especially if thats a 100 crop, the bird must have been pretty far away. its a sharp lens though (looks at grass)

[René Damkot]

The actual AF field is bigger then the red rectangle in the VF. Furthermore: It likes contrasty subjects to focus on. In this case the grass presents a much easier target then the black bird. So it takes the easy way out, and AF'es on the grass.

[willg]

The actual AF field is bigger then the red rectangle in the VF. Furthermore: It likes contrasty subjects to focus on. In this case the grass presents a much easier target then the black bird. So it takes the easy way out, and AF'es on the grass.

good to hear, now that its getting warmer, I will take this big lens out more often and try to get some big subjects next time

[gcogger]

I agree 100% - the grass is a much easier target for the auto-focus, so it simply focusses on that.

I'm not sure what to suggest to get round that, except to ensure that your subject is the highest contrast object anywhere near the focus point.

[lost]

If I had to crop the photo anyway I would just focus at his feet. So that even if it does focus on the grass the bird is in focus. You also have full time manual on the 70-200l so if it is not hitting the focus point you want you can overide it.

[basroil]

that's a pretty sharp 100% crop, just means your focus was off. if i had to guess, you tried focusing near the neck of the bird, and the higher contrast grass blades were chosen instead of the bird.. just wait until some dslrs in the eos line have the eye focus control thing in some of the film ones.:D

[In2Photos]

If I had to crop the photo anyway I would just focus at his feet. So that even if it does focus on the grass the bird is in focus. You also have full time manual on the 70-200l so if it is not hitting the focus point you want you can overide it.

Yup, try this or even his beak as the contrast between beak and the rest of its body is very high. That lens should be very fast to focus so make sure you are focussed on the correct thing before you snap the pic. Also, don't be afraid to stop the lens down to f/5.6 or higher so that even a slight misfocus could still land a decent shot. At 200mm your DOF can get pretty shallow.

[lon10c]

Center AF point looks for contrasty, horizontal and vertical lines and the area covered by the AF point is larger than it looks in the view finder. AF point simply, as others have said, locked on the grass behind the birdie

In sports photography it is called "getting fenced", where AF locks on a fence or the bleachers behind the player. When shooting at birds in a bush it's a crap shoot as to what the camers AF point will like most. I usually use AF to get in ballpark then fine tune manually. (where C.Fn-4 comes in handy)

At a 20 foot distance with the 200 at f4.0 you have a total depth of field of 8 inches; therefore if the birdie is about 4 inches from focal point it will be OOF.

[clengster_77]

try focussing the body of the bird or any bigger part of your subject, i think your focussing the bird's eye thst's why it mis focussed.

[Keiffer]

Funny thing, since I got my 30D this has happened alot lately. I'm not sure what the problem is, well I know it's not the lens because I didn't have this prob with my D60.

[willg]

thanks for the tips guys. I will try to be more aware and see how it turns out

[Juan Zas]

That was exactly the problem I had with my first 70-200 f/4 L. After 100 shots, I decide to do the focus test chart to confirm the problem and it did. I sent back, received a second one, and it works perfectly !!! Tack sharp. So if you are in doubt, try it:

http://www.canon-dslr.com/Canon_Jan05/Canon_SLR_Focus_Test.htm

[Jon]

I should have thought that there'd be enough contrast between the bird and the grass for the AF to pick up on that to focus on, giving you a good crisp bird, if the lens were focussing properly. The way it is, it looks like you're back-focussing. Try a couple of other shots in similar conditions, and if it persists, move to the focus test before sending it in.