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No AF fine-tuning....

Discussion in 'Olympus Cameras' started by Dave in Wales, Apr 6, 2015.

  1. Dave in Wales

    Dave in Wales Mu-43 All-Pro

    Nov 5, 2011
    West Wales
    There is no facility for AF fine tuning on Oly or Panny M4/3 cameras, but there is on Nikon and Canon.
    Now why is that, not that I want it, I'm just curious.
     
  2. beanedsprout

    beanedsprout Mu-43 Veteran

    429
    Apr 13, 2013
    north central Ohio
    It's not needed because the AF is based off the sensor, while DLSR cameras focusing mechanism is bounced off a mirror first, and there might be slight variations in distance between what is in focus in the viewfinder and when the mirror flips out of the way and light hits the sensor. The sensor determines what is in focus on mirrorless cameras like the ones from Olympus and Panasonic, taking a step out of the equation compared to cameras with mirrors and prisms.
     
  3. tkbslc

    tkbslc Mu-43 Hall of Famer

    DSLR focus without actually seeing the image. That wasn't possible with film, anyway. They use sensors that read differences in light wavelengths and predict how far the AF mechanism needs to travel to achieve focus. It is very accurate as long as the lens is starting where the AF mechanism thinks it is. If it is off, then there is a big problem. Let's say the AF mechanism needs focus to move to position 17 to achieve focus. The lens should be starting at 0, so the AF is told to move 17. Well what if it is calibrated wrong at it is started at -2? Well then when it moves 17, it will be at 15, not 17. Camera has no idea there is a problem because lens moved exactly as far as it was told. So you have front focus. Calibration ensures the AF is starting at 0.

    Mirrorless focus by looking at the image right on the sensor and confirming focus by comparing contrast. It is rather obvious when that is in focus and it can adjust realtime as the focus is being achieved. The downside is that all this sampling causes extra processing and calculations that the DSLR doesn't have to do. That's why tracking is faster on a DSLR (or with DSLR type phase-detect sensors) they only calculate once.

    Theoretically, the EM-1 could need calibration for lenses since it can use phase AF.
     
  4. wjiang

    wjiang Mu-43 Hall of Famer

    The E-M1, A6000, X-T1 and others all feature PDAF on the sensor. None of these require calibration as the PDAF is being driven by detectors right on the sensor plane - calibration is required for SLRs because the phase detectors are not located on the sensor/film plane.
     
    • Informative Informative x 1
  5. tkbslc

    tkbslc Mu-43 Hall of Famer

    That can't eliminate the possibility of a lens being out of spec. It doesn't matter if it is at the sensor plane or not. It is not using the actual image to focus so if the lens isn't moving where it is supposed to, the camera will not be able to tell and AF will be off.

    Just as I suspected, browsing the E-M1 manual there is a typical AF microadjust setting detailed on page 110. Just like with a DSLR.
     
  6. wjiang

    wjiang Mu-43 Hall of Famer

    Fair point, I guess with the 4/3 PDAF-only lenses the fine adjust is still required for lens errors. For m4/3 lenses I'm not sure it's required (or even used?) during full 9 FPS PDAF driven C-AF. Anybody with an E-M1 care to comment on whether AF micro adjust applies to m4/3 lenses?
     
  7. DaveEP

    DaveEP Mu-43 Top Veteran

    684
    Sep 20, 2014
    York, UK
    Not having fine tuning (for regular M43 focusing) is in my opinion one of the major advantages of mirrorless systems.

    While I understand that DSLR focusing systems can perform faster in some situations (e.g. sports) I have absolutely no use for that in the things I shoot. I frequently got mis-focussed (front / back) shots from both Canon & Nikon DSLR systems but since using M43 (both Panasonic and Olympus) I've yet to get an OOF shot using native M43 AF lenses that wasn't obviously user error.

    I have absolutely no desire to go back to DSLR systems. While I still have some Canon lenses, I'd rather pick up a Sony mirrorless to go with them than another Canon DSLR, and even then, I'd rather carry a Lumix 35-100 f2.8 than a Canon 70-200 f2.8! Damn, talking myself in to selling these things!
     
  8. kevinparis

    kevinparis Cantankerous Scotsman

    Feb 12, 2010
    Gent, Belgium
    Actually it does exist on the E-M1 in Section K of the Gearwheel menu - never used it !!

    K
     
  9. T N Args

    T N Args Agent Photocateur

    Dec 3, 2013
    Adelaide, Australia
    call me Arg
    You have probably got the main point from reading the above replies, i.e. the Canon and Nikon systems have an in-built flaw that requires manual adjustment of individual cameras and lenses to focus accurately, whereas the systems used by most mirrorless cameras are inherently free from that flaw.

    And you are quite right to not want it. :laugh1:
     
    • Agree Agree x 2
  10. Ross the fiddler

    Ross the fiddler Mu-43 Hall of Famer

    The E-M1 does have AF-Fine adjust (particularly useful for correcting 4/3's lenses) & it is possible to change the settings for M4/3's lenses as well (at least it is in Firmware 3.0). Maybe that is because C-AF uses a combination of PD-AF & CD-AF for M4/3's lenses.
     
    • Informative Informative x 1
  11. Dave in Wales

    Dave in Wales Mu-43 All-Pro

    Nov 5, 2011
    West Wales
    Thank you one and all...!
     
  12. Ross the fiddler

    Ross the fiddler Mu-43 Hall of Famer

    Actually, the first Olympus DSLR to have it (AF fine adj) was the E30, so the E-M1 is following on from then (including the E620 & E5).
     
  13. Fri13

    Fri13 Mu-43 Veteran

    353
    Jan 30, 2014
    The sensor PDAF doesn't need the calibration. That is the question why Olympus added the function to calibrate each focus point. What is when lens focus is off because lens element being off-center.

    But when image plane is same as PDAF focus metering plane is, there is no mis-focus because PDAF itself. The problem is when PDAF is on different plane than image plane (other than in lens).

    The mirrorless cameras use CDAF, it means it moves focus group in lens and meters contrast. It does overshoot to see when strongest contrast is lost and returns there. CDAF doesn't have any misfocus problems, as long subject has enough contrast.
     
  14. tkbslc

    tkbslc Mu-43 Hall of Famer

    To fair, I think that should be worded as a "possible" flaw. The large majority of DSLR shooters will never find their AF to need calibration and will find their camera and lenses to focus well from the factory.
     
  15. DaveEP

    DaveEP Mu-43 Top Veteran

    684
    Sep 20, 2014
    York, UK
    It's also fair to say that the vast majority of DSLR users don't realise their occasional (or not so occasional) soft shot could be fixed by the tweaking now available. In years gone by some people would sell (or return) a lens because it was 'soft' when in reality it just needed in-body tuning. Likewise, some people sold their lens as being 'sharp' but the buyer thought it was 'soft'.

    Another major flaw in the plan of the DSLR tuning was that I found a zoom lens may need (say) -5 on the wide and but +10 on the telephoto end. Now what?
     
    • Agree Agree x 1
  16. jeffryscott

    jeffryscott Mu-43 Top Veteran

    505
    Jul 2, 2010
    Arizona
    They will at least never notice that their cameras/lenses could be calibrated and be better! Sarcasm aside, you are correct. I do suspect that if these owners did look critically, there would be room for improvement. But, with kit lenses in the 3.5 to 5.6 range, there probably is no real need for calibration, it is only noticeable with faster, higher grade optics, which most owners of any brand will never buy.

    Back on topic, I'm using the E-M1 with a 50-200 SWD and EC-14 and have not noticed a need for calibration, but, I've also not specifically tested. I may have to try just out of curiosity ...
     
  17. T N Args

    T N Args Agent Photocateur

    Dec 3, 2013
    Adelaide, Australia
    call me Arg
    Sorry, but that's completely untrue. Unless you mean they will never find it needs calibration because they will never test it properly and they will never realise how their keeper rate could be higher -- because general experience when people do the micro AF calibration tests properly is that adjustments are needed. Exhibit 1: an interesting article on the topic by Michael Johnson. In particular under the heading "SLRs must be aligned too" where he writes "I have never seen a camera come from the factory in critically sharp alignment for use with a reasonably fast prime lens."
     
  18. tkbslc

    tkbslc Mu-43 Hall of Famer

    I'm certainly not convinced, having seen way too many razor sharp photos from SLR cameras and lenses. However I'm not really interested in trying to convince you. Have a good one.
     
  19. Clint

    Clint Mu-43 All-Pro

    Apr 22, 2013
    San Diego area, CA
    Clint
    Then for an Olympus E-30, E-5, or E-M1 you adjust both the close and far distance accordingly!
     
  20. Ross the fiddler

    Ross the fiddler Mu-43 Hall of Famer

    Yes, that is right & if you suspect different results over the whole AF area, you can also adjust each (AF area) individually if desired.

    PS To be pedantic, the E620 (& E600?) also has that feature.
     
    Last edited: Apr 7, 2015