Lens won't focus

Discussion in 'Canon EOS' started by graham_brown|1, Jun 19, 2013.

  1. Hi there. I'm hoping someone may be able to help me here.
    I have a new ( 3 month old) EOS 650D, which was purchased with the standard 18-55mm lens plus a 75-300mm telephotos lens. Until yesterday, all was fine. Now the 75-300mm lens will not focus properly. If I aim at the subject, say a wild bird sat on a fence post, the camera just can't decide what to focus on. The lend whirrs in and out, I can't press the shutter button halfway for an AF lock, and can't take a photograph as the lens will not focus. Occasionally, after whirring for around 10 seconds, the lens will eventually focus, I get the AF lock, and I can take the photo but this doesn't always occur. Even on a shaprly contrasting subject, say a red brick house against a blue sky, the lens will not focus.
    I've had a couple of error messages along the lines of " there is a bad contact between the camera body and lens" or something like that, so I have cleaned both sets of contacts with alcohol and a low lint cloth but it makes no difference. The lens is set to AF rather than MF, and the camera battery is fully charged.
    Any ideas anyone please? Many thanks
  2. Hi Graham .Welcome to P.N. Try setting just the centre point AF, could be too many AF points trying too hard ! Hope that helps Miken
  3. The camera needs two things for focus to work: contrast and light. If you are shooting in low light, or in low contrast situations, or if you are shooting with the sun in the frame (where lens flare can cause focus issues as well) your camera may not be able to focus.
    I would certainly try using the center focus point as a test. It is odd that the lens won't focus on a red brick house against a blue sky. I would try some other subjects (ones that are far enough away that you're not running into the close focus limit of the lens) just to be sure.
  4. Graham . Is the 70-300 a Canon or a third party, sigma tamron et al, Miken
  5. How often are you getting the error message? If it is consistent, and you say cleaning the contacts doesn't help, there may be a problem with the lens. Are you having a similar problem with the 18-55? Have you tried focusing on the same subject with both lenses?
  6. What were you shooting immediately before you had the problem with AF? If you go from shooting something 20 feet away to something 100 yards away or vice versa, you can be so far out of focus for what you're trying to shoot that the AF won't work. You might need to give the AF a little help by turning the focus dial manually to get the object or scene you're trying to focus on at least somewhat in focus before you can deploy the AF and it can lock in without hunting all day.
  7. Many thanks to all for your replies. It is a Canon lens, their EF 75-300mm 1:4 - 5.6 III. I've just come back in, I took the camera out with me, a microlight went over the top, no more than 300 feet up, very bright lime green wings against an even white sky yet the 75-300mm would not focus on it at all. No AF lock, no nothing, no AF points in the viewfinder.
    The problem isn't present when I use the 18-55 mm lens, all is fine.
    OK, Mike and Rob, I have set just the centrepoint AF and it does seem to work OK now. I've fired off a few shots from the garden of objects at various distances and the lens focuses almost immediately and produces a clear, sharp image. A light aircraft has just flown across the area here, lined it up on the centre AF point and it focused perfectly. I shot the photos on the "P" setting which still automatically sets the aperture and shutter speed. On the fully automatic setting, it still seems reluctant to focus as presumably then, it is using all the AF points.
  8. Well ,all seems ok Graham glad to help, Miken
  9. [[it still seems reluctant to focus as presumably then, it is using all the AF points.]]

    You're correct. In P, Av, Tv, and M, the camera will allow you to select focus points. But in automatic modes, you give up control of the focus points.
  10. Is there a distance range switch on that lens? Many of the longer tele-zoom lenses have one. In one position, the lens will try to focus on all possible distances and this can be very slow or even lead to a situation such as the one you describe. There is typically an alternate position that restricts the focusing range to further subjects - and that is the setting you normally want to use for subjects that are not extremely close.
  11. (1) Before you tried the center-point focus, what were your focus settings? I can imagine that if you had it on fully automatic focus and were trying to catch a bird against the sky, you might have a hard time, because the camera might never "see" the bird to focus on. But if you are aiming at a scene with detail in it, and the light is reasonable, the camera should at least lock on something (I'm thinking of your brick building example).
    But, if you had inadvertently selected an off-center focus point, then even the building-against-sky photo wouldn't work, because the camera might be trying to focus on the sky. So I get back to my starting question.
    (2) I would remain concerned about the error messages, even if the lens works on center-point focus.
  12. Dan, that lens doesn't have a distance limitting switch.

  13. Thanks Barry, I've not had the error message since yesterday morning now and I use the camera all the time. Maybe there was a tiny piece of grit or something between the contacts?I'll wait to see whether or not it reappears. Thanks again to everyone for their comments and assistance, it's much appreciated.
  14. Ruben wrote: "Dan, that lens doesn't have a distance limitting switch."
    Thanks for pointing that out. I'm not familiar with the lens.
  15. My dad has the same problem with the 75-300 mm Canon EF Lens. The lens and his Canon XT were caught in a rainstorm. The Shutter in the Camera slowed down tremendously and the lens doesn't focus like yours. Canon couldn't fix either so the camera is just slow and the lens is nearly junk. Most repair centers will charge more than you would like and since the lens is on the cheeper side of Canon Lenses, he decided to buy a new one. If you don't want to pay full price I suggest buying from a used Camera place. I bought from KEH once and they were really good. I found the lens you have on their website. You can choose from different grades based on percent of original condition and what it has (hoods and caps). https://www.keh.com/212515/canon-75-300mm-f-4-5-6-iii-ef-mount-lens-58
    Hope this helps
  16. Hi,

    I registered here to say I have EXACTLY the same problem. With three different lens the camera has trouble focusing even on bright and contrasting shots.
    Using the 27 point AF causes the problem. If I manually specify the central point it is fine.
    An interesting thing I noted is that I was on firmware 1.0.1 to begin with and never had the error message about a bad contact.
    After updating to 1.0.4 I started to get the message appear. BUT, it only appeared when using M or AV modes.
    Any creative mode worked fine.
    Then to make it stranger, the error message appears to have gone away now. However, I`m still wondering why it has so much trouble focusing on AF.

    My camera is out of warranty now ( only a year with Canon it seems ) , and I was hoping the firmware update would have fixed it.

    Has anyone else here had similar problems? Or better still did they find a solution?


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