Focus Problem with 24-70L, I'm About to Return It! - Please HELP

<p>Ok, so here's the problem I'm having with this supposedly amazing lens: When zoomed all the way out to 24mm, and I try to focus on the subject, then reframe to take the picture, my focus falls to the background rather than staying on the subject which I originally focused on. This happens on almost all images taken at 24mm with this lens. Is this a lens defect or am I doing something wrong? <br>

Here is the camera and settings that I'm using:<br>

Canon 40D<br>

One Shot - Focus Mode<br>

Shutter speed - plenty fast enough to stop motion (often around 1/200)<br>

Auto focus point set to center point; I aim the center point at the subject, halfway depress the shutter to set focus, then recompose to set the subject off center and fully depress the shutter (I've used this method with the 18-55mm IS and 50mm 1.8 and have had no similar issues)<br>

Please help because I'm ready to send the lens back! WAY too expensive of a lens to be having these kind of problems. Thanks.</p>

<p>Sounds like an operator error if this doesn't happen for focusing without reframing.<br>

Do you see the focus shift after you press the shutter to take the picture? [if you had the camera on the tripod and looked through the viewfinder after]<br>

You said you're not in AI-Servo... you said One Shot, otherwise that would do it.<br>

And you're sure you're keeping the shutter halfway pressed while recomposing?<br>

If this was a problem with the lens, you would be the first one to have that --- it has to be problem with the camera or operator...... i'd vote for operator error :-)</p>

<p>I hope it is operator error, but I am just confused as to why this problem RARELY came up with my other, much less expensive lenses. I don't see the focus shift after the picture is taken but the subject doesn't seem as sharp in the viewfinder as it does when I'm zoomed in either. Almost like it's having trouble finding focus while zoomed out. I am definitely conscious of keeping the shutter halfway depressed while recomposing. Any other ideas of what I might be doing wrong?</p>

<blockquote>

<p>And you're sure you're keeping the shutter halfway pressed while recomposing?</p>

</blockquote>

<p>I think that is the most likely explaination of the problem. Once you press the shutter half way down the camera will focus. IN one Shot focus mode, once the camera is in focus it is locked and the focus will not change unless the finger is lifted off the shutter. Nothing in the lens would cause this. The lens will only change its focus when the camera body tells it to. So I wouldn't return the lens.</p>

<p>The only other possible user error I can think of is that you are changing the zoom after you set focus. on most zoom lenses if you change the zoom setting after locking focus you will also change the focus</p>

<p>ditto for Steven and Roberts' point on somehow not keeping the focus lock on when you're reframing.</p>

<p>On many early zoom lenses, you often needed to refocus a tad after altering the zoom, but I wouldn't expect that here. I don't have this particular lens, but is it possible to hit the focus ring when you are working the zoom? In any case, I'd wait until you identify for sure which end of the camera body the problem is on before shipping the lens back.<br>

Perhaps also call the vendor and tell them you're having a problem and see what they say about it. That will give them some warning about return as well. When I had a somewhat similar problem with another lens (I found out it <em>was</em> operator error), I called the vendor and they immediately gave me a return authorization, but fortunately I saved everybody's time by finding out what I was doing wrong before I sent it back.</p>

<p>Do a test simply focusing on something and shooting without recomposing the shot. If those are sharp its not the lens or camera. </p>

<p>Do you change the zoom setting after you focus and re-compose? That would explain the issue you are having. Always focus at the same zoom setting you will be taking the picture with.</p>

<p>I don't change the zoom setting while re-composing so that's not it. I realize that it MUST be one of 4 things:<br>

1) I may be accidentally nudging the focus ring while holding the lens (I've never had a lens with a focus ring so close to the zoom ring)<br>

2) I may be accidentally releasing and re-depressing the shutter after recomposing (which would explain why the center/background is more often in focus) but I have been SO conscious of not doing this, and have never really had an issue with this with my other lenses<br>

3) There may be an auto-focus problem with the camera (wouldn't make much sense since I don't experience this with my other lenses)<br>

4) The lens just isn't as sharp as my other lenses (18-55 IS, and 50mm 1.8) which is HARD to believe unless I literally have a "lemon" of a lens.<br>

I have a friend who has the same lens, and we're going to try it out on my 40D tonight and see if the issue is me, or something else. </p>

<p>There is a setting on your camera to "Focus only when a certain button is pressed, NOT when pressing shutter half-way".<br>

"certain button" is AF-something, it's on the top in the back. If you used that custom function, then pressing the shutter halfway wouldn't do anything. What you would do is press that button (AF-something), so you focus, then recompose (without moving, and you want to move the camera as little as possible to remain close to the the plane of original focus), then you would press the shutter button to take the picture.<br>

This is a temporary setting you would use, to isolate the problem area. This way you'll know the focusing is not being changed with the shutter button, so the problem lies elsewhere if the problem still happens after this.<br>

Have you been retrying your problem since you wrote the original posting yesterday?</p>

<p>Hmm interesting, I'll have to try that custom setting. Yes, I shot an engagement session last night, being very conscious of the issue and trying to be dead on with focus, and about 70-80% of the shots were unusable. SO frustrating. </p>

<p>I believe a simpler solution would be to get a 1D4, just to be sure it's not something with the 5D2 (or actually it's 40D you have, oops) :-), and you get more focusing points of course.<br>

Sounds like you are handholding, probably at f/2.8, with subject pretty close, just 4 feet or so perhaps?<br>

As far as zooming after focusing, i would not think it's only the early lenses that would not be in focus after zooming, i would re-focus after zooming always on any lens, just to be sure [but i don't think you are doing that in this case].<br>

Chances are that you are quite close to your subject, and re-composing could be "too coarse", you might focus with center point when actually you want to focus not that close to the center [so use a closer focusing point] - you would to move the camera as little as possible after focusing, and definately you don't want to change an angle at which the camera is -- you want to move the camera slightly, not your body, which you might do without knowing you are doing it.<br>

That custom function I described in the posting above this one, have a look at it in the manual, i know for sure 40D has it, it could be AF-Lock function, just look at all the Custom Functions and you'll find it, or in manual in the Index under Focus-Lock or AF-Lock or AF-ON.</p>

 

<p>Is this lens new or new to you?<br>

I would call 800-OK-CANON, they have tech support that has patience and suggestions, and they might have heard your issue before. They resolved my issue which turned out to be an operator error as well.</p>

<p>Yes it is both new and new to me. </p>

<p>I have a 7D and 24-70. I don't think it is your lens. Here is what I would do at this point.</p>

<p>(If the 40D doesn't have micro focus adjust function then disregard that info)</p>

<p>1. Assign your focus to the * button so you now use your thumb to focus and never again will the shutter button be used to focus. You will never regret it and wonder how you got along before you did it.<br />2. Set aside some time and get out the tripod and do some testing. Make sure at 24 mm your autofocus is focused without any recomposing and shoot. If it isn't focused, then adjust with microfocus. <br />a. if you get sharp images there is nothing wrong with the lens or the autofocus</p>

<p>b. if you can't get sharp images with AF and adjusting through microfocus, then try getting sharp images with manual focus as seen through Live View at 10 X magnification.</p>

<p>c. if you get sharp images then there is nothing wrong with the glass in the lens but there might be a problem with AF/camera/or the camera-lens combo and sending the lens alone back will not solve the problem.... unless you get a replacement lens that matches the camera better.</p>

<p>I'm wondering if your original shooting was done at 2.8 giving a shallow depth of field. Recomposing can signiicantly change the distance of the subject to the film plane.</p>

<p>Keep us posted.</p>

<p>Richard</p>

<p> </p>

<p>You might want to post a 100% crop to illustrate what you mean. Blurriness can come from several places--from camera shake and subject motion to DOF to camera/lens calibration to user error. Still, there is another factor, which is one's ability to work with the lens. This particular lens has a reputation for being borderline troublesome re focus accuracy. I belong to a professional wedding forum, and even some experienced wedding pros have given up on this lens. Some have been driven to Nikon because of flaky Canon focus--many times, <strong>with this lens</strong>. Others do fine with it--so there is that personal factor in there too.</p>

<p>However, it won't hurt to review some basic issues when autofocusing. I outline them in the following thread.</p>

<p><a href="http://www.photo.net/canon-eos-digital-camera-forum/00WYJl">http://www.photo.net/canon-eos-digital-camera-forum/00WYJl</a></p>

<p>In particular, the fact that it is difficult enough to focus accurately with wide focal lengths already (target areas tend to be small in the frame), and then you add autofocus on top of that, and with a cropped sensor camera, the fact that the focus points are bigger than marked. I have a 16-35mm, and when I use it on my 5D at the wide end, I double check my focus on the distance scale, and sometimes focus on people's feet (if parallax won't be an issue) to avoid subject edges 'encouraging' the autofocus to back focus.</p>

<p>It is also good to compare with another 24-70mm on your camera. Process of elimination is a good thing.</p>

"This particular lens has a reputation for being borderline troublesome re focus accuracy. "

 

I tought it was just my lens, but I occassionlaly ran into some focusing dificulties with this lens especially in Dim lighting situations. The lens would hunt and hunt like there was no tomorrow even though I tried focusing on contrasty areas. Despite that, it is an extremely sharp lens sometimes too sharp if you are shooting portraits. Not sure but aren't you suppose to use the AE lock that's the '*' button on the back of the camera to lock the exposure ?

Here is a 100% crop to show the issue that I'm having. My intention was to focus on the man's face in this shot but it appears to me that the focus fell to the trees in the background.<div></div>

<p>The image I uploaded was shot at the following:<br>

F/4, ISO 100, 1/200s, 24mm</p>

<p>That's pretty terrible.<br /> Composition could be better too, to get all green background, none of the white sky, so back them up, stand more up, all green behind them in the picture, zero sky.<br /> Did you not notice the lack of sharpness on the spot? I mean when you recomposed, took the picture, kept the camera on your face, didn't you see the focus has shifted?<br /> I don't see anything in focus, not even the background.<br /> That separate button for focusing would have definitely helped I think, push it once to focus, slightly reframe, done.. take a picture, or more, focus is where it should be.<br /> If I was in your situation I would be thinking about returning the lens too..... but i would make sure to eliminate user error...... which you are doing... so it's all good.<br /> And in the future if you have to use a lens with "issues" think about manual focus and tripods, but those do introduce a delay.... but increase quality, no matter if the lens is good or bad. And with Live View you can get 5x and 10x magnification [on some cameras] so that you can manually focus and get the focus right without any kind of recomposing. Slows you down, so you only get 10 Great shots......... vs 100 crappy ones?<br /> Besides the lens issues, using a tripod will make you be more critical of the photo, since you are not busy balancing your weight as you're half crouched and thinking about how uncomfortable you are -- on a tripod you will pay more attention to composition and catching a moment when things look optimal.<br /> Even if it is "on tripod" with a loose ballhead, at least then the up-down motion is stationary.<br /> <img src="http://robertbody.com/people08/images/2008-06-01-alex-0290.jpg" alt="" width="750" height="500" /><br /> I don't usually use a tripod for portraits, there is usually no time for that (and i don't mean my time, I mean subject's time... or in this case above, the seconds and minutes of the Good Light)<br /> but this one was with a tripod<br /> <img src="http://www.robertbody.com/animals08/images/2008-07-24-zoo-puma-40d_7848.jpg" alt="" width="750" height="500" /><br /> unless specifically the people want their photo taken, then you should use a tripod definitely<br /> <img src="http://robertbody.com/weddings/images/2007-08-04-ula-park-girls.jpg" alt="" width="750" height="500" /><br /> no sky...</p>

<p>Robert, this is a 100% crop from a much larger image (with better composition :) ) The original image was too large to upload, but did a better job of capturing their surroundings. No, I don't notice the focus shift, but like Nadine said, on a 24mm shot, the subjects are fairly small in the frame (well at least their faces are) so when I THINK I'm focusing on the face, it must be rather going to the background, or somewhere in between. I still need to try setting the custom button for focus. I took some pictures with my friend's 24-70 last night and couldn't really tell any difference in sharpness (but we were indoors at 800 ISO as well). I just still think it's SO weird that I never had to worry about this with my cheap 18-55 kit lens. Sure I had a few out of focus shots, but not anything like the amount I'm getting now. </p>

<p>The background does not look all that sharp either. Is there an area of obviously sharp focus?</p>

<p>Not really. The background looks the sharpest to me, and I agree, that's not very sharp. Here's a link to the full size image - h<a href="http://chriswphotography.smugmug.com/Other/My-Smug-Mug/10407550_2qUXg#902562437_7V6Xq-O-LB">ttp://chriswphotography.smugmug.com/Other/My-Smug-Mug/10407550_2qUXg#902562437_7V6Xq-O-LB</a></p>

<p>It looks to me like the focus is just behind the couple, where the rocks meet the water, and probably extending into the water for a bit. Where did you put the focus point?</p>

<p>I think you have a choice to make. Either return it for another one and see if it is better, or test the heck out of this one. Including the usual front/back focus test, and applying some of the suggestions above re use of the lens. Can you not conduct more precise tests with your friend's lens?</p>

<p>The focus point was supposed to be the man's eyes, but again this was a 24mm shot. I'm looking into the front/back focus test right now so I'll make sure that's not the problem. Yes, a better test would have been to have the camera on a tripod outside, take a shot with my lens, take a shot with my friends lens and compare. I'll try to set that up as well. </p>

<p>Can anyone recommend a good resource for reading about and testing front/back focus?</p>