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Thread: Would like some help with my lense

  1. #1

    Would like some help with my lense

    I have upgraded my camera to the Canon T3i, and along with it I ordered the 55-250mm lense. My problem is that I don't believe I am using this lense to it's full ability. I take a fair amount of photographs of the birds and other wildlife were I live, but am unable to zoom as close as I'd like to (the lense has a lot farther to go to get to 250). Could someone please tell me what I am doing wrong? I've searched and searched, and cannot find an answer to this, so I'm hoping someone can educate me.

    Sorry if this questions sounds like it is coming from a newbie, but I understand how to use the camera just fine, only having trouble with learning how to use the lense, which I've never used before.

    Thank you in advance for any help that you can give!

  2. #2

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    Re: Would like some help with my lense

    I'm not quite sure to understand your problem. You zoom and unzoom the lense and when at 250mm (On the zoom ring) it's not as close as you'd like it?

    Maybe 250mm is not enough for your need. Maybe you need a higher focal length.

  3. #3

    Re: Would like some help with my lense

    When I take the focus manually up to 250 for a closeup of a subject, it is blurry (guess I should have mentioned that in my initial post).

  4. #4
    Moderator Dave Humphries's Avatar
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    Re: Would like some help with my lense

    Quote Originally Posted by srooney View Post
    When I take the focus manually up to 250 for a closeup of a subject, it is blurry (guess I should have mentioned that in my initial post).
    Hi Mathieu,

    Is the Image Stabilisation switched on?
    Have you got Auto-focus switched on and working properly?
    Do you see it attempt to focus?
    What shutter speed are you using? (should be at least 1/320s)

    Please post an example image.

    Cheers,

  5. #5
    RockNGoalStar's Avatar
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    Re: Would like some help with my lense

    Are you too close to your subject? The minimum focus distance of the Canon EF-S 55-250mm f/4-5.6 IS Lens (I assume this is your lens) is 3.61 feet / 1.1 metres. If your lens is closer to the subject than this then you will not be able to get the subject in focus.

  6. #6

    Re: Would like some help with my lense

    Quote Originally Posted by Dave Humphries View Post
    Hi Mathieu,

    Is the Image Stabilisation switched on?
    Have you got Auto-focus switched on and working properly?
    Do you see it attempt to focus?
    What shutter speed are you using? (should be at least 1/320s)

    Please post an example image.

    Cheers,
    Dave~

    I can answer yes to all of this. When I zoom in fully to 250, the focus is clear. But when I look at the length that the lense is at, it appears that it can extend further, and will do that when I switch it to manual focus (but picture is blurry). When I saw this, I was hoping that I would be able to zoom in even farther on my subject. Apparently I was wrong.

    Thanks for your help!

  7. #7

    Re: Would like some help with my lense

    Quote Originally Posted by RockNGoalStar View Post
    Are you too close to your subject? The minimum focus distance of the Canon EF-S 55-250mm f/4-5.6 IS Lens (I assume this is your lens) is 3.61 feet / 1.1 metres. If your lens is closer to the subject than this then you will not be able to get the subject in focus.
    No, I'm plenty far from the subject, so the focus distance isn't the issue.

  8. #8
    ktuli's Avatar
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    Re: Would like some help with my lense

    Ah - I think I know the issue here.

    A zoom lens like that will change length both for the zoom and focus functions. So the lens being at its longest focal length does not necessarily mean it will also be at its longest physical length. You will notice that two separate parts of the lens will move - one while changing the focal length, and another (usually the part furthest from the camera) while changing the focus.

    Extending the lens to its longest physical length will only work for one specific focal length and focusing distance (ie: subject distance).

    - Bill

  9. #9
    FrankMi's Avatar
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    Re: Would like some help with my lense

    I suspect that Bill is right on. Change the focal length from shortest to longest and watch the lens while you do. If it is like mine it will grow shorter then longer as you increase the focal length. The internal lens components are changing their relationship to one another inside the barrel of the lens as you adjust. It is quite normal for some lenses.

  10. #10

    Re: Would like some help with my lense

    So with that figured out, if I keep moving farther away from the subject I am trying to capture, the focal length (lens) will continue to lengthen as it focuses on the subject? I will have to play with that and see if works. Will let you know!

    Thanks Bill & Frank!!

  11. #11

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    Re: Would like some help with my lense

    Quote Originally Posted by srooney View Post
    So with that figured out, if I keep moving farther away from the subject I am trying to capture, the focal length (lens) will continue to lengthen as it focuses on the subject? I will have to play with that and see if works. Will let you know!

    Thanks Bill & Frank!!
    Yes and No... (not helpful, I know)

    When discussing the focal length of a lens, we actually mean the focal length with the subject at infinity. That's the one you change when zooming in or out (between 55 and 250 mm in your case). And you change the focal length by moving some parts of the lens. Visually, you'll see the lens getting longer.

    But, that's for a subject very far away (infinity). If the object gets closer, you'll have to move the whole lens away from your sensor/film surface to get a sharp image. conversely, moving the lens too far away, gives you a blurry image again. This also looks as if the lens gets longer.

    So, in both cases the lens seems to get longer, but in one case, only some elements move, in the other, everything moves. If you try the different controls (zoom and focus) with the lens off the camera, you'll notice a difference in what parts move (if you do this, don't forget to put a cap on the camera body and be careful about dust).

  12. #12
    Glenn NK's Avatar
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    Re: Would like some help with my lense

    Quote Originally Posted by ktuli View Post
    Ah - I think I know the issue here.

    A zoom lens like that will change length both for the zoom and focus functions. So the lens being at its longest focal length does not necessarily mean it will also be at its longest physical length. You will notice that two separate parts of the lens will move - one while changing the focal length, and another (usually the part furthest from the camera) while changing the focus.

    Extending the lens to its longest physical length will only work for one specific focal length and focusing distance (ie: subject distance).

    - Bill
    I too believe this is the problem. I had a Tamron 35 - 85 zoom on my Canon A-1. It would get longer up to about 75 mm in focal length, then past that to 85 mm, it shortened slightly.

    Another thought is that the OP might have been focusing manually past infinity. This will result in OOF images too.

    Glenn

  13. #13
    Moderator Dave Humphries's Avatar
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    Re: Would like some help with my lense

    I think we are now 'on the right track'.

    Many telephoto lenses will "focus breath" (I think it is called), as has been said, the lens will be 250mm when focused at infinity, but may well be significantly 'shorter' than that, say equivalent to 200mm focal length as subject distance reduces.

    Basically, you have no control, so;
    IF you're concerned about the len's physical barrel length; forget it
    IF you're concerned about the image being bigger when it is blurry and smaller when sharp; forget it
    IF you're concerned about the subject not being close enough, buy a longer lens - if you can afford it

    It's just one of those things I'm afraid

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