photo:olympusem5_af

optimising autofocus on the Olympus OM-D whilst using Micro Four Thirds lenses

introduction

  • the E-M5 boasted the fastest AF for single shot AF on stationary or slow moving subjects of any camera produced up until that time, thanks to further improvements in the Olympus FAST AF technology and the AF motors in the latest a brief catalogue of Micro Four Thirds lenses.
  • one area that is slow to unusable is continuous AF tracking of moving subjects as the E-M5 does not have phase detect sensors which are currently required to ensure fast C-AF with tracking.
  • no matter which camera you use, it cannot predict which of the many subjects in a scene you actually want to focus upon, and when using lenses with shallow depth of field (DOF), this aspect becomes a critical factor and REQUIRES YOUR INTERVENTION - after all YOU are the photographer and YOU should be deciding this and NOT the camera.
  • the OM-D cameras try harder than many cameras to do this for you if you let it:
    • it can preferentially look for a face in the scene and the AF on the closest eye - only Olympus cameras have this very cool technology
    • it can find the object within your selected AF region which is closest to camera
    • the Olympus OM-D E-M1 mark II has an extended range of tools to assist in ensuring accurate focus for a range of scenarios

these tips are largely applicable to other MFT cameras such as the Olympus E-PL5, E-PL6, E-P3 and E-M1

optimising auto focus

  • set Picture Mode = Vivid (gives faster AF)
  • avoid using C-AF modes unless using cameras with PDAF such as the E-M1 - in other cameras it is faster to use S-AF instead for moving subjects
  • turn off fulltime AF
  • although AF-assist light (“AF illuminator”) is available and may help in dark situations with subject not too far away, I have never needed to turn it on, and having it on is distracting, so I leave it set to OFF
  • use a lens with a wide aperture, particularly in low light (the f/5.6 kit lenses are a touch slower than wide aperture lenses in low light)
  • avoid using dark filters such as ND or polarising filters
  • whilst one can use the default settings and just half-press the shutter you will get variable results as the camera will select an almost random subject to AF upon although it will prioritise a face if Face Detection is enabled.
  • alternatively, you could just use the touch screen and touch a subject and the camera will almost instantaneously AF and take the shot - very impressive indeed and handy for SOME situations.
  • consider using a focus limiter if available
    • by restricting the range the lens will hunt through, you can not only have the AF acquisition sped up substantially, but also have it ignore closer or more distant subjects (very handy if you are shooting fish in behind glass, wildlife behind a wire fence or a foreground foliage in front of a bird)
    • some lenses have 2 or 3 options as a switch on the side of the lens
    • in addition, the E-M1 Mark II can do this in-camera on all MFT and FT lenses with far greater versatility:
      • Menu: Cog: A1 : AF Limiter = ON then right arrow to select range
    • the E-M1 Mark II also allows the camera to control a user preset focus limiter range - very handy for difficult circumstances!

AF may NOT work in some conditions:

  • AF may not be possible (AF mark will blink) if either:
    • inadequate contrast in subject (eg. a blank wall or blue sky)
    • strongly backlit subjects or very bright lights near subject
    • no vertical lines
    • subject is too close
  • AF may lock onto the wrong subject if:
    • subject is moving quickly
    • intended subject not within selected AF region
    • there are interposed foreground objects such as dirty windows or wires of a cage

how can YOU control what the camera will AF on?

technique 1: half-press shutter release S-AF with prefocus and recompose

  • improve AF by reducing AF region to the small central region then move camera so that subject is in the centre, press S-AF to set focus (eg. half-press shutter or press AFL/AEL button if set to AFL in S-AF), then recompose
  • to change AF selection to ONLY the centre square, in shooting mode, press the left rear arrow button, and this will display the AF area grid.
    • press INFO button and this allows you to:
      • select Face Detect mode via left/right arrow buttons
      • select the size of the AF region by adjusting with the up/down arrow buttons
    • use the down arrow to get to just one AF region, and ensure this region is in the centre by again pressing INFO button to leave that mode so you can use the arrow buttons to move the AF area around.

  • this is the default mode although default is set to allow all AF regions
  • to avoid it randomly selecting subjects to AF on, ensure the AF region is made as small as possible and centre your subject on the AF area then half-press shutter then full press shutter to take the photo
  • this setting also allows you to use the touch screen (see bottom of page) to select AF and immediately release shutter
  • can be a pain if you have to hold the shutter in half-press for long periods

  • you cannot assign AFL to a AFL/AEL button AND use half-press shutter to lock AF, you have to choose one or the other - see the AF mode settings for S-AF
  • for slowly focusing lenses or difficult to AF subjects, my preference is to set AF mode to S1C2M3, and have the camera mainly set to manual focus mode, that way I can use the AFL/AEL button to perform S-AF and lock it so I don't need to be holding the shutter button half down for long periods.
  • if I want to use the half-shutter for AF as is usual for most cameras, just set AF to S-AF instead of MF

technique 2: C-AF

cameras without PDAF

  • this can be useful for moving subjects
    • in the early PEN cameras it did NOT work well with subjects moving towards or away from the camera
  • set AF mode to C-AF (not C-AF + tracking unless large subject)
    • many feel the C-AF mode works better for them than C-AF + tracking for fast moving subjects
  • set AF field to a smaller group to reduce risk of camera getting side tracked and AF on another more contrasty subject (this is not possible in C-AF + tracking)
  • set EVF rate to HIGH (NB. this will not be possible if you have focus peaking enabled or assigned to a button!)
  • on the E-M1, you can set drive mode to burst rate High and 9fps, otherwise you may have to settle with Low at 4 to 6.5fps on other cameras
    • NB. in H burst, you can only get AF with each shot if in C-AF mode, and in this case it is PDAF only!
  • set IS to IS1
  • set Half Way Rls with IS = ON (this activates IS on half-press shutter and speeds AF locking)
  • set image stabilisation to ON for burst mode if IS is needed, or turn it off if faster burst rate is needed
    • for E-M5: set “burst mode IS OFF” to OFF (if you want IS in burst mode)
    • for E-M1: set “burst mode image stabilisation” to ON (if you want IS in burst mode)
  • use Shutter Priority mode for action shots so you can choose your shutter speed to stop the action
  • consider setting the default Menu:Cogs:C:Rls Priority C to OFF to reduce number of out of focus shots but this will reduce number of shots taken as camera will take shot only when AF is achieved and not at the usual selected burst rate
  • to further optimise CDAF, set Picture Mode to Vivid with Contrast +1, and noise filter off
  • NB. C-AF seems to work better at longer focal lengths and better with Olympus than Panasonic lenses
  • compose frame so that your desired subject is in the centre of the frame where the AF region is
  • half-press shutter await AF confirmation beep and start shooting
  • if the subject lock is lost, you will have to re-acquire it again
  • PRACTICE!
  • you can assign a button to perform 'AF stop'. By default, this function seems to be assigned to the L-Fn button. Pressing and holding the button will temporarily stop C-AF. This can be used for example when something moves in front of your subject for a short time, or when your subject is out of the frame for a short time (you have in the order of 0.5 sec after loss of tracking to press this button and interrupt C-AF without the camera forgetting the object it was tracking)1).
  • if there is significant delay between acquiring AF and shutter release, this technique will be a nuisance as you have to keep shutter release half-pressed and the battery life will be affected
  • unless you are panning, ensure C-AF Lock is set to Low, normal or High rather than OFF
    • C-AF lock keeps the focus at the correct distance if you lose the subject out of focus for a some fractions of a second
    • if you are panning, then consider turning C-AF Lock to OFF.
  • the E-M1 appears to use ONLY PDAF if either:
    • a Four Thirds lens is used, or,
    • shooting C-AF with H burst mode (when shooting in L burst mode CDAF is also used, when shooting in S-AF at with CDAF-compatible lens, only CDAF is used, and only for the 1st frame)

cameras with PDAF

  • see also:
  • do not use C-AF Tr mode - use C-AF instead!
  • the E-M1 Mark II allows 18fps burst rates with C-AF and as long as you keep your subject within the AF region you have selected to use, it has a good chance of maintaining AF!
  • to help the camera out you can:
    • turn face AF OFF - may not make much difference but it should simplify the algorithms
    • use the in-camera AF Limiter to ensure camera does not focus on foreground or background, plus it speeds up the AF process by using a shorter range of focus distances within the lens - you can rapidly disable this by using a lens focus limiter instead, or you can set a Off/On toggle with option to select 1 of the 3 presets if you allocate a function button to AF limiter, and alternate mechanism is to use the custom modes to switch shooting styles.
    • consider using 9 point AF instead of single point to have a better chance of AF lock on subject

technique 3: AF lock back button AFL pre-focus and recompose

  • this is great for situations when there is constant camera-subject distance such as static scenes, subjects at a distance, or fast moving subjects when AF will not work and you can set a focus for where you anticipate the subject will be.
  • my preference is to leave face detection on, but set the AF region to the central square only, and ONLY activate AF by pressing the AEL/AFL assigned button.
  • this enables you to pre-focus on your subject and then you are always ready to get the shot without waiting for AF as long as the subject to camera distance has not changed.
  • this is a technique many professionals use, and is particularly handy in situations where AF is sluggish such as very low light, or low contrast subjects.

here are my configurations to enable this functionality

  • go to the Menu by pressing the Menu button
    • select Custom Menu (the cog wheels icon)
    • select AF/MF
    • select AEL/AFL then for MF set it to mode 3
      • AEL/AFL should now be S1/C2/M3
      • this will mean that you can use camera set to MF mode and then half-down shutter will lock exposure while AEL/AFL functionality (which, by default is assigned to Fn1 button) will activate S-AF briefly to lock the focus
  • while you are in the Custom Menu system (see Disp/PC sub menu, Beep icon), you may want to turn the AF Beep noise OFF – you can just look for the green AF confirmation light instead, it will be much less distracting for others and your subject.
  • I prefer to set AF Illumination to OFF (this is really distracting for subjects, and this camera works pretty well in low light without it if you use wide aperture lenses)
  • I also prefer to set Face Priority to AF on near eye if doing a single person portrait (some may prefer to turn this off but it seems such a cool feature for portraiture)

technique 4: AF for fast moving subjects without PDAF

  • whilst the C-AF+tracking is too slow to retain lock on fast moving subjects (unless you have a PDAF capable camera such as the E-M1 Mark II), the incredibly fast S-AF may well suit your needs better
  • having the default camera settings with AF mode set to S-AF, just full press shutter release when the subject comes into the AF region - don't bother with half-pressing to lock AF, as Nike ad says - just do it!
  • you may wish to have your AF region occupy the central half rather than the smallest point or the full area to give you a better chance the camera will lock on to the subject you want.
  • if shooting in burst mode without image stabiliser:
    • setting burst mode to L for 4fps should give reasonable AF for each frame although I need to see which mode works better S-AF or C-AF in this instance
    • setting burst mode to H for 9-10fps will lock AF on the 1st frame only, so this is fine if the camera-subject distance does not move out of your depth of field (DOF) range during the burst

technique 5: AF for narrow or tiny subjects

  • trying to AF on a small flower as part of a much larger scene can be impossible using the default AF method
  • instead use Super Spot AF mode via:
    • AF mode to S-AF + MF or MF (if using MF alone, ensure you have set AFL/AEL to AFL in MF mode via AEL/AFL setting = M3)
    • set Fn2 button to Magnify (or MultiFunction then select Magnify)
  • press Fn2 TWICE to activate Magnify (remember you can rotate dial to adjust magnification)
  • manually focus the lens until the subject is almost in focus - this will give it sufficient contrast and magnification that the AF will then preferentially AF on it instead of some background object as is usually the case
  • then half-press shutter to activate AF if using S-AF + MF mode, or press the fn button allocated to AFL if using MF mode as per technique 3 above
  • remember, half-press shutter will also activate IS for you to stabilise the image to enable easier MF and AF assuming you have this enabled

technique 6: face detection AF

  • I love this mode, and particularly the closest eye option
    • the camera will try to identify a face - this is indicated by a white square appearing around it even before you activate AF
    • if the camera is able to detect the subject’s eyes, it will display a green frame over the selected eye, then when you half-press shutter, the focus will be locked onto the nearest eye in preference to your selected AF region(s).
  • there are several issues with this mode that need to be kept in mind:
    • if your subject turns and the camera no longer detects a face, the camera will AF on the subject in your selected AF region potentially leaving the face out of focus
    • sometimes you need to wait a fraction of a second for the camera to identify a face, don't be too quick on the shutter - you might get your selected AF region instead.
    • there is no way to preferentially select a particular person if it identifies more than one face
      • the newer Olympus OM-D E-M1 does allow you to register a number of faces to take preference

technique 7: use the touch screen on the LCD to select AF subject and trigger the shutter

  • this can be a very handy option
  • it is generally incredibly fast
  • obviously LCD screen must be active as the viewing device
  • the LCD screen can be set to:
    • touch disabled
    • touch triggers AF
    • touch triggers AF then immediately releases shutter

technique 8: use the touch screen as an AF target pad to select AF point

  • eg. E-M1 Mark II (not on earlier OM-D models)
  • great for portraits when Face Detection AF is unreliable (subject too small, not looking at camera, wearing glasses, or constantly moving) or for off-centre subjects
  • use the viewfinder to compose scene while the flipped out LCD screen is used as an AF point selection pad
    • I recommend having the screen flipped out as this reduces risk of your nose accidentally moving the AF point
    • BUT for this to work with a flipped out screen, you need to turn off the eye sensor EVF Auto Switch and select the EVF to be the viewing device
    • IF you also want the screen facing the subject (but then the AF pad will be reversed), you also need to turn off selfie mode as otherwise the screen will become the viewing device not the AF target pad
  • turn on AF Pad via Menu: Cog : A2 : AF Targeting Pad = ON (unfortunately this cannot be assigned to a button but could be assigned to a custom setting on the PASM dial)
  • consider having Fn1 button set to AF Home and have the AF Home set to centre point (Menu: Cog : A2 : AF Home then press right arrow button and then the 2nd item of the icons - set this to centre point)
    • this allows you to rapidly move the AF point back to the centre point by hitting F1

technique 9: preset manual focus combined with AFL for focus pulling

  • eg. E-M1 Mark II (not on earlier OM-D models)
  • assign Fn 2 or REC to Preset MF
  • activate Preset MF mode by pressing the above button
  • to change the preset distance, either:
    • press AF mode button on top left of camera, then INFO button the set focus eg. by using AF half-press then to store the distance, press OK, or,
    • press OK to open the Super Control Panel (SCP), move cursor to select Preset MF cell then press OK then press INFO button as above
  • Note that this works as if you are in MF mode, thus if you have set A1: AEL/AFL to M3, then you can press the AEL/AFL button to get an instant AF lock on another location then if desired hit the Preset MF button to return to your preset focus distance - very handy, particularly if you are not confident AF will lock for you and you want a back up manual focus plan locked onto the distance you expect the subject will be.
  • this could potentially work in video work as a focus pull technique
1)
thanks Bart
photo/olympusem5_af.txt · Last modified: 2017/10/29 19:57 by gary1