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infinity focus calibration

Discussion in 'Photography Tips, Tricks & Tutorials Forum' started by Randall8, Aug 9, 2018.

  1. Randall8

    Randall8 Member

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    The infinity focus on my Samyang 12mm mft lens got messed up all of a sudden (is there a reason for this ?)

    So basically there's no point where the image is in focus.


    Has anybody had this issue before and was able to repair it by themselves at home ?
     
  2. Andy 0

    Andy 0 Always on Premium Member

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    Something is wrong here.

    At 12mm focusing should be far from critical, at these super-wide angles things are generally pretty close to being in focus at any reasonable distance.

    Does the focus ring rotate smoothly and to the full extent of its travel?
     
  3. hooferinsane

    hooferinsane EXIF Seeker Super Moderator

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    I have a 12mm Samyang and no problems with it. Did it used to focus ok at infinity? If it suddenly has just started happening, I would send the lens for a service /repair - can it focus ok at say, one metre? Sometimes Samyang lenses are known to leave the factory with poor focus scale calibration.
     
  4. Randall8

    Randall8 Member

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    Sure, it used to work perfectly fine for a year..
    I use it on my Panasonic GH5 (m43 sensor) so it's effectively 25mm.

    The focusing ring turns smoothly, but when at the infinity focus mark, things are just not in focus...

    And the 1year warranty is over by now..

    Therefore I was wondering if it can be repaired at home.. if not, I'll be forced to send it for repair (which will most likely not be cheap)
     
  5. Andy 0

    Andy 0 Always on Premium Member

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    Can you get infinity focus with manual focusing?
     
  6. paulmag

    paulmag Always on Honorary Life Member

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    if you are relying on the distance marks being accurate dont .............use eyeball mark 1 to verify plus at f8 on a lens that focal length its difficult to be out of focus infinity is a long way to focus .....atmospheric haze would be an issue.

    can you focus on things you can see 10 100 or 1000 metres away OK
     
  7. Randall8

    Randall8 Member

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    I think when I turn the focusing ring way to the maximum (past the infinity focus mark) things that are really far away (200-300m) are in focus.
     
  8. MikeB

    MikeB Always on Premium Member

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    As I understand the conversation, the issue only occurs at the infinity mark where the image is not in focus, but objects at infinity will come into focus when the lens is turned beyond infinity. This issue is new to the lens.

    Seems to me that you may have dropped the Samyang 12mm or gave it a good whack and a lens element or lens group is no longer properly aligned.

    As you can still achieve focus the issue is not critical, however it may be worth it have a qualified repair shop evaluate and repair the lens.
     
  9. SeanNeedham

    SeanNeedham Ol' Sparky Honorary Life Member

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    This is one of them where without looking at the lens itself (and a comparison lens of the same type) I don't know if it's part of the design of the optics or it's damaged; if you want piece of mind go off to a repair shop and have it checked. However a modern AF lens (not one with the hard focus stops) will focus beyond infinity by design (and I think that's what you're describing here) and the close field of focus will disappear.

    The other thing is, ignore "infinity" as infinity on a lens is variable (and hence why the infinity mark on some lenses is a parallel line to the mount not a singular mark). Where the focus of infinity will be shifts due to external conditions (like heat, haze, atmospherics, lens tolerances, filters, normal/IR cameras) and really it's not an accurate form of focussing. From a technical point of view, infinity is really the wrong word for it (as shooting on a hot day with haze, it could be in as close as say 15km; but on a clear moonless night it'll get stars that are billions of light years away) as it's more the area of maximum focus.
     
  10. Ozzie_Traveller

    Ozzie_Traveller Active Member

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    G'day Randall

    I've also been lurking here reading the occasional posts too
    I agree with others that all modern lenses traverse beyond "supposed infinity" in order that the electronics can confirm actual focus

    Q- does a photo of an object more than 50 metres away come into focus okay? ---do objects as close as 1-metre come into focus? ie: is the camera's focus mechanism working?

    ps- via the 'rules of optics', a camera lens distance to infinity equals 1000 times the focal length ... so a 20mm lens has infinity at 20,000mm or 20-metres

    Hope this helps
    Phil from the great land Downunder
     

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