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Focus micro-adjust

Discussion in 'Sony Chat' started by Roger_Provins, Jan 18, 2010.

  1. Roger_Provins

    Roger_Provins Well-Known Member

    Just spent an hour or so micro adjusting the focus on my Sony a900 with a Sony 70-300mm G SSM lens. It's the first time I've found a lens that needed it and the process took sometime before I was happy with the setting - turned out to need +13. Having done it once I think I'd find it quicker if there's a next time. Case of understanding just how much or little the increments from +20 to -20 change the focus point.

    There must be many camera/lens combinations in use that are not optimal in this regard. I imagine many folk are getting sub-par results without realising. I wonder also if reviewers ever check the equipment for back/front focussing before testing?
     
  2. LargeFormat

    LargeFormat Well-Known Member

    I have the same combination. How do I do it?
     
  3. Roger_Provins

    Roger_Provins Well-Known Member

    Page 130 in the manual. Switch micro-adjust on and then click (use centre of joystick) on "0+/-" and scroll up and down to select and click on the adjustment you need.

    I used a 12 inch rule on its edge set diagonally from me at about 5 feet. AF on the 6 inch mark take a shot then see what's actually in best focus and adjust accordingly.

    + makes the focus point move away from you and - nearer to you.
     
  4. Dorset_Mike

    Dorset_Mike Grumpy Old Fart

    Is this something you have to adjust each time you change between this lens and any other?
     
  5. Roger_Provins

    Roger_Provins Well-Known Member

    No, the camera has an internal database where it hold the adjustment for up to 30 lenses. So when a particular lens is mounted it knows and automatically makes the correction.
     
  6. cpfc12

    cpfc12 Well-Known Member

    Just following on from this old post which I remembered as rather interesting, I assume that I can do this on a Ziess lens as well as it is a Sony product?
     
  7. Roger_Provins

    Roger_Provins Well-Known Member

    Yes any lens. The only problem could be if later you try to set the focus adjustment for another lens that mimics the same lens identification numbers or a genuine Sony/Minolta that has that identification. If it's a Zeiss AF lens designed for Sony cameras there should be no problem.
     
  8. Malcolm_Stewart

    Malcolm_Stewart Well-Known Member

    And beware if you buy a used camera with this feature - it may hold the correction(s) for the previous owner's lenses.
     
  9. Roger_Provins

    Roger_Provins Well-Known Member

    Good point. If you get a S/H camera check the menu item for micro adjust and if it's set on, turn it off. Or do a complete reset.
     
  10. cpfc12

    cpfc12 Well-Known Member

    It is a Brand new 24/70 AF from Warehouse Express, mating to a Sony A900. Incidentally the page ref now is 132 and the camera now has the series 2 update.
    I see you used a ruler. I thought I would use a proper lens chart that came free some years ago on stiff card,lying it flat and diagonally away from the camera
    I also notice that the instruction book says under actual shooting conditions, whatever that means? I think that I will set the camera up for AF of course and a mid lens exposure. Or maybe I might see any adjustment needs better at either end of the scale. What's your take on that?
    Finally I have 1 Sigma lens 50mm 1.4 and a Tamron 100mm macro lens. The book says that if I try this on them I could upset the Sony Minolta adjustments. Has anyone tried this on other makes?
     
  11. cpfc12

    cpfc12 Well-Known Member

    Sorry, one other thing. You say about 5ft away and a focus point of 5'6"what sort of hight did you fix the camera above the subject?
     
  12. Roger_Provins

    Roger_Provins Well-Known Member

    You'll see the precise focus point better using the lens wide open to get the shallowest DoF. I'd first quickly try it at both ends and in the middle of the zoom range using a target with about 2cm spacing at a 3-4 meters. Only if there is any doubt would I bother proceeding further with a more elaborate set-up.

    The problem using micro adjust with non-Minolta/Sony/Zeiss Sony AF fitting lenses is that there's no sure way of knowing which lens data they are mimicking. Should it happen to be the same as a Minolta/Sony lens you own the wrong adjustments will be applied to that Sony lens.
     
  13. cpfc12

    cpfc12 Well-Known Member

    Completed this afternoon. No adjustment needed, spot on as far as wide open is concerned. Much harder to call at f11 and f22 but could not see any real point in changing after adjusting +- 3 looked no different to my eye.
    Thanks for all your help Roger.
     
  14. Roger_Provins

    Roger_Provins Well-Known Member

    More or less the same here - only one of my lenses benefited from adjustment.
     
  15. MickLL

    MickLL In the Stop Bath

    Just got round to some tests on my key lenses. All were perfect except for one odd result.

    MY (Very old) 28-85 zoom is perfect at the long end but seems to be out at the short end.

    Any ideas?

    MickLL
     
  16. Roger_Provins

    Roger_Provins Well-Known Member

    If the focus is way off at one end but okay at the other I'd say the lens has a fault - which you'll not correct with micro-adjust.
     
  17. MickLL

    MickLL In the Stop Bath

    Maybe faulty. As I said it's very old. The difference isn't great - maybe half an inch from a distance of a couple of metres.

    In any event it's a lens that I only ever use for 'happy snaps' so I'm not that bothered.

    What's even more interesting (and I never thought that I'd even come close to saying this) is that I reckon that I could spot the difference in pictures taken with this lens and with my 'best lenses'. This zoom seems to lack the bite that the others have. I'm not really comparing like with like though. The zoom was, in its day, the Minolta kit lens and the comparison is a macro prime that cost more than the camera that it was purchased for.

    MickLL
     

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