Help with 70-200 f2.8 L IS

Hi Everyone,

I don't know where to turn---some of my pictures with this lens are tack sharp and then sometimes I get nothing but blur. I am not ruling out user error. I got this lens as an anniversary gift, but getting consistant quality is hard and I'm getting frustrated. I was shooting at 2.8 AV Autofocus. Please help, what am I doing wrong?

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On the second shot you clearly focused on the background.

I would guess user error.

btw.. what other lenses do you use and how often wide open at close subjects ?

It's user error. Get familiar with knowing how to control your focus points on your camera. In short, try using center point only.

Yep, not the lens, sorry.

Sorry to say, but it looks like user error. What do you have your focus point/points set at?

If you want the subject (I presume the people as in your second pic) then aim at the subject first and half press your shutter butter to focus, then readjust again your composition by centering on the background but without releasing your shutter button. In this manner your subject should be sharp.

Another method to keep both the subject and background sharp is to use a smaller aperture to have a greater depth of field.

Happy shooting!

In the first one, the cat took up a good percentage of the frame, so your AF point caught it and you got good focus. In the second photo it looks like your AF point locked onto the background, which resulted in the people and animals being out of focus.

Are you letting the camera choose your focus point, or are you choosing it yourself? Pay attention to which focus point turns red in your viewfinder when you get the AF confirmation beep - that's where your focus will be.

I don't like letting the camera select AF points - it often doesn't choose the one I want. You'll get much better results if you use the center point and focus/recompose (hold the shutter release halfway down to hold focus while recomposing), or manually select your focus point.

start by not using the automatic focus point selection mode.. you'll see a big improvement

Instead of telling her its user error provide ways to help.

For example. I think most AF points are BS. Set it so that its the center point is the only one it uses. Then set your camera to One Shot. This allows you to focus on a point, readjust the composition then snap the picture with it locked to that focus.

Also remember the shutter speed/focal length rule. Always keep it higher than your current focal length for safe measure. If you are shooting at 50mm keep your shutter about 1/50. If you are at 200 keep it above 1/200.

Also I just noticed you shoot with an XTi. So your focal lengths are actually multiplied by 1.6

+1 on the ridiculousness of AF points. Like rojethee and others mentioned, make sure to set the focus point to what subject you want in focus.

Also, XTi is especially stupid with AF points. There are times when there's a person right in front of the camera and it'll focus on a random object behind the person.

Also remember to let the IS play for .5 seconds before you take the picture. If you don't than you will have a picture that is not sharp.

One thing about "focus and recompose": If you are using a higher aperture such as f5.6 and up, this method will give you decent results. If you are using it wide open, your DOF will be razor thin and any recompose you perform will more than likely place the subject out of focus.

Your focus plane is parallel to your sensor. Let's assume your subject is about 20feet away and you want a nice close up so you zoom in all the way to 200mm (~320mm full frame equivelant) your depth of field will only be a little under 4inches in thickness with around 1.8 inches in front and 1.8 inches behind your subject (obtained from a DOF calculator). If you recompose your shot, chances are you will lose focus on your subject since you "shifted" your focal plane. Now, there is no need to calc this stuff out but it is good to know how "wide" your focus plane will be aroundish when composing your shot. Something to think about.

Hope this helps.

tl;dr: If wide open, the best option is to compose first and select your focus point. If stopped down a few stops then recompose should be ok.
Rob

robbug wrote in post #8280259
One thing about "focus and recompose": If you are using a higher aperture such as f5.6 and up, this method will give you decent results. If you are using it wide open, your DOF will be razor thin and any recompose you perform will more than likely place the subject out of focus.

Your focus plane is parallel to your sensor. Let's assume your subject is about 20feet away and you want a nice close up so you zoom in all the way to 200mm (~320mm full frame equivelant) your depth of field will only be a little under 4inches in thickness with around 1.8 inches in front and 1.8 inches behind your subject (obtained from a DOF calculator). If you recompose your shot, chances are you will lose focus on your subject since you "shifted" your focal plane. Now, there is no need to calc this stuff out but it is good to know how "wide" your focus plane will be aroundish when composing your shot. Something to think about.

Hope this helps.

tl;dr: If wide open, the best option is to compose first and select your focus point. If stopped down a few stops then recompose should be ok.
Rob

You have to be conservative with how much you compose something like Rob said. But slight recomposes should be okay on most wide open fstops

Everyone, thank you! I figured it was me--and I have reset to use only the center focus point. The ones I've taken since have been much sharper. I have always shot on full auto in the past---and I'm trying to get better with actually using the abilities of the camera and wonderful lens that I have. I'm heading out to shoot some wild horses this weekend, so taking the advice here, I may not try to shoot wide open, but will step it down some, and hopefully come back with some decent shots.
Again! Thank you all for your help! I do appreciate it.

There's definitely a learning curve on the 70-200 zooms. For me, I had learn what exposure speeds I could get away with when using IS and not using IS. I also had to learn when to use IS and when not to use IS. You'll love your lens when you get used to it. Have fun with it.