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AP Focussing Test Chart

Discussion in 'AP Magazine Feedback & Suggestions' started by Bawbee, May 27, 2011.

  1. TimF

    TimF With as stony a stare as ever Lord Reith could hav

    When Michael Reichmann reviewed the original LensAlign on Luminous Landscape he included a short video, which if I recall made mention that it is possible for zooms to require differing correction at different focal length settings. Might be worth watching; it's near the foot of the page.
     
  2. GeorgeIII

    GeorgeIII Well-Known Member

    Thank you. In the video he says that on a zoom you can only make the adjustment on a single focal length because you can only make one adjustment per lens. He adds that you should choose the longest FL available on a zoom as this is likely to prove the most effective adjustment throughout the range – presumably because of the smallest DOF. One would have thought this rather essential point would have featured in the AP article.
    George
     
  3. Benchista

    Benchista Which Tyler

    Surely common sense would tell you that? :confused:
     
  4. RogerMac

    RogerMac Well-Known Member

    Some cameras allow more than one adjustment for each lens, for example different values for wide and telephoto settings. Not that I see any need to use this faciity on my camera.
     
  5. Roy5051

    Roy5051 Well-Known Member

    Could we have a list of DSLRs with Fine Focus Adjustment facility, please?
     
  6. Malcolm_Stewart

    Malcolm_Stewart Well-Known Member

    From p47 of the AP article:
    Canon Eos
    1D Mark III
    1D Mark IV
    1Ds Mark III
    5D Mark II
    50D
    7D

    Nikon
    D300
    D300s
    D3
    D3X
    D3S
    D700
    D7000

    Olympus
    E-30
    E-620
    E-5

    Pentax
    K20
    K-7
    K-5

    Sony
    Alpha 900
    Alpha 850
    -----

    Hope I haven't made any errors
     
  7. Roy5051

    Roy5051 Well-Known Member

    All top-flight machines. Shame about the rest, then.
     
  8. Malcolm_Stewart

    Malcolm_Stewart Well-Known Member

    I'm only familiar with Canon, and last summer I deliberately bought a used 50D so as to get the AF MA feature in a much more compact body than the 1D Mark III. The near mint used copy in makers box etc. cost me £499, and having the AF MA has allowed me to get the best out of my lenses - some of which need a setting close to 20, the maximum.

    At the time, I doubt if any Canon fanboy would have regarded the 50D as "top-flight"! The more glamorous 7D had arrived, and the 50D doesn't do video, and it hasn't got the 7D's better AF & weather sealing. A year on and used prices of 50Ds appear to have risen slightly.
     
  9. RogerMac

    RogerMac Well-Known Member

    Olympus grade their offerings by the number of digits and would not claim their E620 as "top flight" good as it is.

    In fact there was a problem with one batch of early E3s and they had to be recalled for modification. No doubt the expense of this exercise persuaded Oly that it was easier to provide this feature across the range than recall a batch, I have heard of no problems with any later batches. Of course CSCs do not need the feature as focussing is done directly on the image sensor.
     
  10. YPhotography

    YPhotography Active Member

    I might be slow, but I get there in the end...

    I just decided to have a go at this, as I've always been a bit suspicious of my AF.

    I had a go with a few lenses in my lounge, and the cheaper lenses all appeared to front focus. My 50mm f/1.4 seemed to vary a lot with distance. My 24-70 seemed bang-on, and I couldn't get far enough away for the 70-300.

    Looking on the net, people were saying that these tilted scales were no good, as the target needs to be parallel to the sensor. This seemed reasonable to me, so I taped a bit of folded card to the side of the sandwich box with a hand-drawn vertical target aligned with the centre line.

    [​IMG]

    My results then went from being front focused to slightly back focused.

    I took the 70-300mm telephoto outside, at the proposed x 50 distance (15m) and the poor thing could hardly see the target.

    [​IMG]

    I worked out that one pixel is about 0.3mm at this range. The top image is a 100% crop with slight sharpening. According to DOFMaster, the DOF on this shot is about 50cm, and visually appears to be still slightly back focused, but so soft that it hardly seems to matter.

    So, not much wiser.
     
  11. Barney

    Barney Well-Known Member

    I think a guage like this is useful for calibrating, but to purely test whether a lens is focusing okay I find that taking a portrait at c45 degrees with spot focus on the nearest eye is the best way, mainly because it's a real world scenario and it's easy to tell what's in focus.

    In terms of calibrating continuous autofocus, I've heard that tracking the front number plates of moving cars is a good test, but tbh life's far too short to waste doing that unless you absolutely have to. I came across this in a discussion on another forum where a number of sports photographers with, IIRC, Canon 1dsMark III bodies were having real issues.
     
  12. Damien_Demolder

    Damien_Demolder Well-Known Member

    I'm using mine to check that the film holder I'm making for my tailboard camera is positioning the film/paper in the right place. Working well so far.

    Mine came with bacon, lettuce and tomato.
     
  13. spinno

    spinno Well-Known Member

    ...perks of the editor I suppose....
     
  14. RogerMac

    RogerMac Well-Known Member

    Damien, what film stock are you using, please?
     

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