Focusing - Any Tips?

Discussion in 'Beyond the Basics' started by Jess, Feb 25, 2005.

  1. Jess

    Jess TPF Noob!

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    I use a manual camera and I'm having a hell of a time with focus. I have one shot in particular that I KNOW I focused on the subject and instead she came out blurry and something behind her is in focus. What am I doing wrong?

    Does anyone have any tips on this? I do wear glasses but if that were the problem I imagine I would see the same thing in the film as through the viewfinder. I do keep my glasses on while looking through the viewfinder.

    I'm so frustrated, any help appreciated, thanx :)
     
  2. nikon90s

    nikon90s TPF Noob!

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    What type of camera are you using? Is it new or could it need to be repaired? Do you need glasses?
     
  3. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Sometimes an eyecup will help. Depending on what SLR you have there may or may not be one available. The Nikon F3 HP has a viewfinder that is supposed to help eyeglass wearers who have trouble with focusing. These days most folks just go AF.

    EDIT: I see you have a Canon. There is an eyecup available.
     
  4. walter23

    walter23 TPF Noob!

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    I read something about focusing & recomposing being bad technique. It looks like you are using a manual focus camera (AE-1) so you can't choose a closer AF point, but you might try doing a slight bit of focus correction if you are dramatically recomposing your shot. This is because the lens focuses on a plane parallel to the film plane, not a spherical surface equidistant from you. If you rotate your camera enough, you move this plane and your subject might no longer be in focus. This is obvious much more of a problem with really shallow DOF, although I'm really not experienced enough to tell if it's something that shows up in practice very much or not.

    I also read this on a technically minded forum where people seem more obsessed with equipment than taking photos. It is technically correct but like I said I don't know if it's actually a significant problem in practice or not.
     
  5. Jess

    Jess TPF Noob!

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    I had to read your post twice before grasped what you were saying Walter, but I get it now and that's a very valid idea. Particularly given that things behind the subject were in focus. I'm a newbie and I got spoilt by the point and shoot that didn't require focusing :)

    Also, thanx Matt, for the suggestion. I'm not sure where to start but I think an eye-cup different from the one I have will help me in more than one way. Although it does make it a pain to change my film. :p

    Good advice, thanx!
     
  6. walter23

    walter23 TPF Noob!

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    I guess you figured out what I meant, jess, but it was sort of cryptic. Here's a diagram I whipped up in illustrator for anybody else (hey, it's a boring night).

    [​IMG]

    Turns out the focusing distance error (E) relates to the angle you've rotated your camera (theta) and the initial focus distance (D) like this:

    E = D - D*cos(theta)

    You can use that plus a depth of field calculator ( http://www.dofmaster.com/dofjs.html ) to figure out if that's really what's going on, if you're obsessive like me.

    Example, if you focused on a subject 10 feet away and rotated the camera 25 degrees, you have focused 10 - 10*cos(25) = ~0.95 feet too far, because your subject is now effectively at a focusing distance of 9.06 feet but you're focused at 10. With a 50mm lens at f/2.8 you'd be just barely outside the DOF (extends to 9.08 feet away), and probably wouldn't notice, but with an 85mm lens you might notice it.

    It is a pretty small effect though so I think in 99.99% of cases nobody would even notice.
     
  7. fadingaway1986

    fadingaway1986 I Burn Easily :(

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    I had this problem last year when i was using a Pentax P30... I was doing a photography course at the time - and the teacher said it was my camera and he didnt think it was me doing anything wrong... So I got a new camera :) I wanted to anyway - this just gave me the push..
     
  8. Rob

    Rob TPF Noob!

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    Beware of modern small framed glasses - especially vari-focals. One of my students had terrible trouble with bad composition due to being unable to see the bottom half of the frame! Some cheap NHS specs later and she was away.

    If possible, use big glasses and an eyecup or preferably a nice F3HP like me :)
     
  9. KevinR

    KevinR TPF Noob!

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    I was wondering if you used or are aware of the split screen focusing aid in your camera? If not, then start using it. Don't just rely on if it looks focused. Another thing is use a tripod. It makes you slow down and that in turn will be a help.
     
  10. Dweller

    Dweller Inconspicuous Supporter

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    I have a Canon AE-1P and have been in denial about my need for glasses for quite a while so I use the split screen as my indicator of good focus. To my eye there may be a range that it seem in focus to me so if I cant use the split screen to get it dead on then I find the points where I see its focused to close and too far and split the difference.
     
  11. Kodan_Txips

    Kodan_Txips TPF Noob!

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    Elementary suggestion really, but if you are using a zoom lens, on a fairly static subject, go to full zoom, focus, check the distance, and pull the zoom back WITHOUT changing the focus. (You check in case you accidentally twist the focussing collar as you zoom to w/a - this can be a problem with one-touch lenses that use the same collar for both functions)
     
  12. Jess

    Jess TPF Noob!

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    I do have the focusing screen on my camera, and I do use it but I have trouble sometimes getting spot on. I think I may not fully understand it. You are in focus when the cross hatching in the circle goes away right? I do have trouble with that aid because I sometimes will have a small range where it looks the same and I'm not sure where to stop in there for best focus.

    I need laser eye surgery, heh.

    At any rate, the photo's I have in mind I swore I had them in focus... maybe I'm leaning forward when I hit the shutter or adjusting the frame just enough and forgetting to adjust the focus w/ it, as Walter suggested. It's so dissapointing though.
     

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