Asahi Super Takumar focus problem

Discussion in 'Photography Beginners' Forum' started by jwalker, May 21, 2007.

  1. jwalker

    jwalker TPF Noob!

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    Hi guys.

    I apologise straight up if I`m wasting your time - I did a few searches but couldn`t find a suitable thread.

    I recently picked up a lovely Asahi Super Takumar 1:2 55mm and hooked it up to my Canon EOS 400D.

    Through the viewfinder everything looks to be in focus ( I even have one of those M42 Adapters with `chip` so I get the red dots and hear the peep ! ) but the resulting photo is horribly out of focus. It`s not a little unclear - nothing in the frame is even slightly in focus!

    Can anybody tell me what I`m doing wrong ?

    Thanks.

    Jwalker
     
  2. Don Simon

    Don Simon TPF Noob!

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    Hi there. Are you sure it's a focus issue and not fungus?

    Also, are you shooting only wide-open at f/2?
     
  3. jwalker

    jwalker TPF Noob!

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    Hi.

    `Fungus`is one of those things I often seen mentioned but am still not quite sure what it actually is !
    It could well be a fungus problem - how would I find out and shouldn`t I see it through the viewfinder ?
    As I said, through the viewfinder everything looks A-OK - even allowing for the fact that the viewfinder image is bit darker, everything seems to be clear and in focus - even Canon`s `auto`focus seems to `see`a clear image !
    Yes, I have been testing the lens at F2.

    Jwalker
     
  4. Don Simon

    Don Simon TPF Noob!

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    Well fungus is basically what it sounds like - fungus growing on or between the lens elements. You would generally be able to tell by holding the lens up to a light; one or more of the glass elements inside may simply look misty, or there might be a speckled or webbed pattern on the glass. If particularly bad you will notice the viewfinder image is unusually dark, but in my experience you wouldn't really be able to see the patterns through the viewfinder, only by looking through the lens itself.

    If it is fungus, I'm afraid there's not much you can do. Exposure of the lens elements to the sun over a long period will stop the growth and may help clear it up a bit, but fungus can't be wiped off like normal dirt.

    I guess one other possibility, if it's not fungus, is oil - there could be some oil leaked onto a lens element. If so it is actually probably a lot easier to deal with than fungus. You will have to take the lens apart, but generally this is not so hard with M42 lenses - just be careful not to touch the aperture blades. But first shine a light through the lens and look through from various angles; this will show any fungus, oil or anything else in there.

    The final and most simple suggestion is simply that the lens is very soft at f/2 and that, combined with a relatively shallow depth of field, gives the impression that the lens won't focus. Also the viewfinders on previous Canon digitals were not all that big or bright so if the 400D is anything like them, that probably doesn't help confirm focus either. Try stopping down to f/8, with a tripod (or a shutter speed faster than 1/100) and a stationary subject.
     
  5. Alex_B

    Alex_B No longer a newbie, moving up!

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    well, try to focus manually by taking several shots with slightly varying focus.


    take a shot along a ruler with marks on it.


    see if anything is in focus.
     
  6. jwalker

    jwalker TPF Noob!

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    Thanks guys - especially ZaphodB.

    I`ve `run`those checks suggested and am pretty sure that it`s not a fungus problem - the results are definitely better at f/8 than at f/2.

    I think at least part of the problem is the fact that, when focussed to infinity, the lens extends both front and back. There`s not enough room in the EOS 400D body to accommodate this so that I`m forced to screw the lens in to about max 80% - depending on the f stop, at f/2 the lens goes in a lot further in than f/8.

    Could I be getting light leakage at f/2 - the lens does feel a bit loose like that ?

    Is there such a thing as a `ring´ I could add to the base of the lens mount to enable me to screw it tight while still maintaining the required distance ?

    jwalker
     
  7. Flash Harry

    Flash Harry TPF Noob!

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    The lens extending inside your camera is the problem, the distance to the sensor/focal plane is incorrect giving you the out of focus on the images, lens are designed to project an image to a set point behind the lens ie:your sensor, if this is closer or further away you will not get a sharp image, it will look ok through the view but I doubt this lens will work well with your camera, ever, you could also damage your camera's mirror so in the long run its not worth it, get compatible lenses. H
     
  8. DSLR noob

    DSLR noob TPF Noob!

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    400D is a cropped sensor, it can tkae lenses farther back. It's series started Canons digital only lenses EF-S.
     
  9. RobinChen

    RobinChen TPF Noob!

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    I'm new to photography and I was wondering if somebody can explain to me how fungus occurs inside the lens?:er:
     
  10. DSLR noob

    DSLR noob TPF Noob!

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    most lenses aren't sealed, if you live in an area with a lot of moisture, like Florida or such, or shoot in a rain forest, or wake up and take a lot of pictures of fog outside. Or if you (in the winter) go outside into extreme cold after the camera was sitting near the fireplace the water will condense of lens elements. no matter how you get water in your lens, even in vapor form, it'll help the fungus grow, just like damp carpet helps mold grow in your house. Some lenses are gasketed and fight moisture with rubber rings/seals between all moving parts.
     

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