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

Discussion in 'Canon EOS' started by tom_collins|3, Jun 13, 2010.

  1. 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?
    Here is the camera and settings that I'm using:
    Canon 40D
    One Shot - Focus Mode
    Shutter speed - plenty fast enough to stop motion (often around 1/200)
    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)
    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.
     
  2. Sounds like an operator error if this doesn't happen for focusing without reframing.
    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]
    You said you're not in AI-Servo... you said One Shot, otherwise that would do it.
    And you're sure you're keeping the shutter halfway pressed while recomposing?
    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 :)
     
  3. 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?
     
  4. And you're sure you're keeping the shutter halfway pressed while recomposing?​
    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.
    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
     
  5. ditto for Steven and Roberts' point on somehow not keeping the focus lock on when you're reframing.
    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.
    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 was 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.
     
  6. Do a test simply focusing on something and shooting without recomposing the shot. If those are sharp its not the lens or camera.
     
  7. 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.
     
  8. 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:
    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)
    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
    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)
    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.
    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.
     
  9. There is a setting on your camera to "Focus only when a certain button is pressed, NOT when pressing shutter half-way".
    "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.
    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.
    Have you been retrying your problem since you wrote the original posting yesterday?
     
  10. 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.
     
  11. 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.
    Sounds like you are handholding, probably at f/2.8, with subject pretty close, just 4 feet or so perhaps?
    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].
    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.
    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.
     
  12. Is this lens new or new to you?
    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.
     
  13. Yes it is both new and new to me.
     
  14. I have a 7D and 24-70. I don't think it is your lens. Here is what I would do at this point.
    (If the 40D doesn't have micro focus adjust function then disregard that info)
    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.
    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.
    a. if you get sharp images there is nothing wrong with the lens or the autofocus
    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.
    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.
    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.
    Keep us posted.
    Richard
     
  15. 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, with this lens. Others do fine with it--so there is that personal factor in there too.
    However, it won't hurt to review some basic issues when autofocusing. I outline them in the following thread.
    http://www.photo.net/canon-eos-digital-camera-forum/00WYJl
    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.
    It is also good to compare with another 24-70mm on your camera. Process of elimination is a good thing.
     
  16. "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 ?
     
  17. 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.
    00Wg9v-252163584.jpg
     
  18. The image I uploaded was shot at the following:
    F/4, ISO 100, 1/200s, 24mm
     
  19. That's pretty terrible.
    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.
    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?
    I don't see anything in focus, not even the background.
    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.
    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.
    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?
    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.
    Even if it is "on tripod" with a loose ballhead, at least then the up-down motion is stationary.
    [​IMG]
    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)
    but this one was with a tripod
    [​IMG]
    unless specifically the people want their photo taken, then you should use a tripod definitely
    [​IMG]
    no sky...
     
  20. 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.
     
  21. The background does not look all that sharp either. Is there an area of obviously sharp focus?
     
  22. 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?
    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?
     
  23. 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.
     
  24. Can anyone recommend a good resource for reading about and testing front/back focus?
     
  25. I tried mine out and at 24mm its probably not its sharpest ( especially wide open ) but mine copy is sharper then the sample you provided. Stopped down it seems very sharp at 24. Note, My test was basically just taking some photos and seeing how they look so not a real scientific test.
    I have heard from a few people that this is not a really sharp lens on the wide end.
     
  26. Thanks Nadine. Well here are the results of my test. It looks to me that the focus is dead on. What does everyone else think? The focus point on the chef guy (with red hair and mustache) was his right eye.
    00WgbC-252487584.jpg
     
  27. 24mm 100% crop
    00WgbG-252487684.jpg
     
  28. 70mm 33% crop (so you can still see the other lines)
    00WgbJ-252487884.jpg
     
  29. Chef guy 100% crop (focus on his right eye)
    00WgbL-252487984.jpg
     
  30. I agree. Does not look like calibration is the issue. On to other things.
     
  31. I was REALLY hoping that was the issue, but I guess not :) I am really in a pickle here because tomorrow is the last day of the return policy to return the lens. I just need to make sure that this lens is right for me (whether or not it has been "right" for others), and I need to decide tonight! I have started using the "AF-ON" focus button that Robert Body recommended and I think I really like that technique (along with disabling the half-press shutter for focus). Maybe that will solve the problem! What would YOU do if you were in my shoes?
     
  32. The decision to make, given the timing, is whether to take the risk of keeping the lens with the idea that you can make things work with it vs. returning it period, with the possibility of wrestling with the issue again after more research and experimentation, perhaps with a rented 24-70mm, or deciding upon a different lens altogether.
    The lens holds its value well, but of course, new is new. You will take a small hit if you sell it later, even if pristine.
    Re the AF button--I agree, it can help, but I find it slower than the half press on the shutter button. Sometimes, it makes a difference, and it may not be the same for you.
     
  33. The fact that it holds it's value well is good to know. The only other lens I've even considered is the 17-55 2.8 especially due to the fact that I'm on a crop sensor body right now. Only downside with that is when I upgrade to the MK II. I just took a bunch more test shots, about to check them out.
     
  34. My opinion, Tom, is that unless you will be upgrading to the MkII within the next 2-4 months, I'd get the 17-55mm f2.8. The 24-70mm on a cropped sensor body is not ideal. With the 17-55mm f2.8, you enjoy that nice range NOW, and the resale on it is probably almost as good as the 24-70mm. Again--just my opinion.
     
  35. I probably won't be upgrading to the MkII in the next 2-4 months, but I suspect it won't be much after that either. I have 3 weddings this year that I'll be shooting on the 40D, but shortly after that I'll be upgrading to the MkII. Would you buy the 17-55 for 3 weddings knowing that after that, knowing that you'd be on the MkII?
     
  36. Perhaps not, but I might return the 24-70mm, rent the 17-55mm for the 3 weddings, and in the meantime, think about and experiment with the 24-70mm separately, or wait until I could experiment with it when I had the MkII in my hands.
    What general purpose lens do you have now?
     
  37. I would also throw this out... Since the 24-70mm in hand seems to be a 'good' one, you might consider just keeping it til you have the MkII. This might seem riskier than just returning it and getting another one, but you have a known quantity now, and ordering another one later might bring you a lemon. Yet another thing to consider. I have to say that an associate of mine has a MkII and uses a 24-70mm with no apparent focus problems (other than the usual), and it is a nice range on a 1.3x crop body. For all you know, it might work better on the MkII.
    I know--doesn't help... :^)
     
  38. My only general purpose lens (besides the in question 24-70) is the 18-55 3.5/5.6. So that's my problem, I really need either the 24-70 or 17-55 ASAP. I'm going to look for some 17-55 vs 24-70 posts because I'm sure there are some.
     
  39. I might also consider buying a used Tamron 17-50mm f2.8. It also holds its resale value well. As far as I know, the 17-55mm is almost as good as the 24-70mm as far as image quality is concerned. About the only negative I have heard is that the IS tends to go out.
     
  40. Before you get rid of the lens, focusing/recomposing at wide focal lengths, especially if you put your subject far to the side of your frame will throw off the plane of focus. There's a nice graphic here: http://blog.duncandavidson.com/2008/09/focus-and-recompose-exposed.html. Have you tried composing your image and then using the nearest AF point to your subject to focus rather than the center AF point?
     
  41. Well I'm really leaning towards the 17-55 now. Thank you so much for all of your help and I'll let you know what I decide!
     
  42. Ryan, thanks for that article, that's very interesting and I suspect that may have been part of my problem. I did however return the 24-70 today (not because there was anything wrong with the lens) and opted to go for the 17-55 since I'm on a crop sensor 40D. I'll definitely keep this principle in mind, and try to get used to moving the AF point when I want to set the subject off-center.
    Nadine (and everyone else), thank you for all your help working through this issue and I'm glad I learned some new techniques because of it!
     
  43. You will really like the 17-55 lens. It is a fantastic performer by any measure, and it's IS function is pretty close to magic. As others have mentioned, it's resale value is very good. Mine is five years old now, and it's used value is almost the same as what I paid for it new.
    The only suggestion I would add is that you buy the factory hood, and use it all of the time. It not only keeps IQ at it's peak, but the hood is nearly bulletproof. It has saved my lens and two cameras from destruction twice already during face first falls on fully extended tripods (both times, a camera mounted 580EX broke in two or more chunks). They also protect the front element from dust, fingers, spray, bangs, and bumps better than any other option short of leaving the lens home on a shelf.
    Here is an example of how well the IS performs on this lens on a 40D in very low light. The shot below was taken inside a TGIFridays in NJ on Dec 20, 2007 at 10:07 pm. Needless to say, it was coal dark outside, and extremely dim inside the bar. The shot was made hand held (elbows on the table top) with a 40D set to ISO 3200. The 17-55 lens was zoomed to 55 mm, and the camera set the exposure at 1/4 sec @ f/2.8. You can see that the woman I photographed was tapping her knuckles on the table, as her fist is blurred, but for a 1/4 second exposure at ISO 3200, there is an amazing amount of sharp detail in the image. The shot was converted to jpg in DPP a day later. The lighting was awful, as it was a mix of various artificial sources from neon signs, and dimmed tungsten bar lamps inside, and a variety of parking lot poles outside, but DPP made reasonable sense of it with a click on her white blouse. Anyway, the 17-55 is a great lens. I think you will be glad that you had trouble with your 24-70...
    [​IMG]
    Good luck with your new lens!
     

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