autofocus browsing by tag


Olympus OM-D E-M1 Mark II + Olympus 300mm f/4 lens – just awesome for water-ski events such as Melbourne’s Moomba

Sunday, March 12th, 2017

I come from a long line of broken Olympus promises when it comes to useful continuous autofocus capability.

Olympus have had C-AF and their even less useful C-AF Tracking modes in nearly every digital camera I have owned – C8080, E330, E510, E-M5 and E-M1 mark I – and sadly, they have all sucked when it came to continuous autofocus on a moving subject, although the E-M1 mark I was a big improvement. Even my super expensive Canon 1D Mark III dSLR AI-SERVO AF mode which was designed for pro sports photographers had sub-optimal AF in this regard.

So, you can see I am used to being let down in this area and was preparing myself for another disappointment.


This weekend it is Melbourne’s Moomba festival and a big part of it is the water ski-ing championships on the Yarra River.

So now I have this opportunity to test out the new Olympus OM-D E-M1 Mark II flagship sports camera from Olympus with their truly amazing Olympus micro Zuiko Digital (mZD) 300mm f/4 OIS lens which makes a comfortably hand holdable kit for the whole day giving 600mm telephoto reach at f/4 aperture with over 6 stops image stabilisation – which may have been a factor in image quality given I was panning madly all day as if I was a tennis umpire.

I am not a sports photographer and this camera does allow a number of settings to allow you to optimise AF algorithms – I left these at their default value, but I did create an in-camera focus range limiter – a novel and unique functionality peculiar to this camera – you can effectively speed up AF and have it ignore the crowds in the background or any foreground leaves. I did find a weird quirk though – the C-AF Tracking mode seemed to ignore the focus limiter settings, so I resorted to C-AF which is almost certainly the thing to do with this camera anyway! You can rapidly disable the in-camera focus limiter by applying a lens based focus limiter – this was handy at times.

The other amazing thing with this camera is the insanely fast electronic shutter burst mode of 18fps with full C-AF, and you can also enable the Pro-Capture mode which I did at the end for the jumps as I lost sight of the skier behind the jump, but Pro-Capture ensures I did not suffer any reaction lag by capturing the 14 frames prior to pressing the shutter – this will be an essential feature for pros one day!

Thus, I shot all my shots in Aperture Priority metering at f/4, Picture Mode = Vivid (I probably didn’t need to do this to improve CDAF speed as for this work we are using the PDAF sensors), Silent Burst Low rate (18fps), with C-AF using the central 9 AF points (the full area seemed less reliable – I hope Olympus add a larger region than just 9 to choose from as getting your subject in this area is critical for AF success!). Depending on whether the skier was front-lit by sun, or backlit, I would adjust the exposure compensation a touch.

When the skier came along I just composed to have them in the AF region, then held down the shutter as I panned – almost no EVF blackout made this possible with a little practice and getting used to the skier’s rapid changes of direction.

At the end you do have to wait for the burst of RAW files to empty from the buffer before you can review them – I just used one card so I could more quickly review them in camera and delete the duds (there were many where the skier was well away from the AF region and thus out of focus – but that was my lack of skill not the camera’s fault). If I wrote a RAW to one card and JPEG to the other card, I would have had to separately delete from each card which would have been a big pain.

Firstly, will the camera C-AF ignore intervening foreground?

then passing behind a tree branch as I panned madly to keep up with him:

Well that was an unexpected awesome surprise! It worked!

Now, the hard one – a 1.5 sec sequence at 18fps with skier covering 50m camera-to-subject distance:

This sequence was shot in much lower light as dark grey storm clouds gathered and blocked the sun, but at least I didn’t have to shoot directly into the sun which could have made the AF more challenging.  This sequence is essentially straight from camera just resized for web.

Here is the 1st of the sequence of 25 shots all taken at ISO 800, f/4, at around 1/800th sec – perhaps I should have used shutter priority at 1/2000th sec and auto ISO:

The 15th frame, still keeping her in focus despite me panning away:

Preparing for her landing, 22nd frame, still in reasonable focus – I think the horizontal distance covered was some 45-50m from what the commentators said:

Yes! a safe landing, 28th frame, acceptably in focus – of all the 28 frames, only 2 were grossly out of focus, and they were mainly because my panning let the subject leave the AF region while the subject was coming towards me very quickly!

I don’t know about you but that craps on my Canon 1D Mark III and what’s more, the image quality in terms of subject sharpness was better than what a fellow I met there who shoots the event every year achieved using a Nikon D3S pro dSLR with a big, heavy Tamron 150-600mm lens which I am guessing is not as sharp wide open as is the Olympus lens, plus the old D3s only as 12mp not 20mp to play with as does the Olympus – but I presume it would beat the Olympus kit when the light faded, plus he had an advantage of being able to zoom out.

OK, I am satisfied – at last Olympus have a winner for sports photography, and the 18fps is really cool, plus being electronic, it doesn’t wear out the mechanical shutter mechanism! Just be prepared to weed through the images and discard those you don’t want, otherwise you will end up with 20-40Gb easily in an afternoon.

Now the technical stuff is addressed, here are some cool beginner shots:

You can click on these for larger size views.

In addition to applying some vibrance, and clarity in LR, the following have all been cropped as even with 600mm effective focal length, they were too far away – feel bad for the full frame guys trying to do this! This were at ISO 400, f/4 and around 1/2000th – 1/6400th sec. In retrospect, in bright sunlight, I should have used ISO 200 to get a tad more dynamic range and image quality, or used auto ISO and shutter priority at 1/2000th sec.

Attaching the leg rope for trick ski-ing:

Cool as she can be:

Somersault action:

Ooops, lost the rope – this is why 18fps beats 10fps – you get to capture action in more detail within the time window:

A B&W somersault:

This guy is obviously having too much fun on the jumps – Olympus mZD 40-150mm f/2.8 lens at ISO 800, f/4, 1/500th sec (I should have used f/2.8 not sure how it ended up as f/4 – perhaps I forgot to check it after changing lenses):

This lady nails it too – Olympus mZD 40-150mm f/2.8 lens at ISO 800, f/4, 1/1000th sec:

No major issues with rolling shutter from the electronic shutter and me panning horizontally with near vertical lines- Olympus has this well controlled although you can demonstrate it if you try hard.

Perhaps Canon and Nikon should be worried – how are they going to integrate 18fps into their sports dSLRs without really giving their mirror system and their mechanical shutters a real working out every time, not to mention the noise from the mirror slapping around!

And, don’t forget, I could have gone to a really insane 60fps with this camera if I didn’t need C-AF – Canon and Nikon could build a dSLR with this but you would have to resort to Live View and hold the camera away from your face to view the rear screen – not great for camera shake!

But if the Canon and Nikon guys are prepared to shell out $20,000 for their pro dSLR plus 600mm f/4 OIS lens, then they could get more background blurring, and shoot at lower light levels thanks to their lower noise at higher ISO – but then carrying this 7kg kit and a monopod around all day would be heavy work indeed! The E-M1 Mark ii plus Olympus 300mm f/4 gives same field of view with faster burst rates plus the option of awesome image stabilised 4K cinematic video and weighs only 1.8kg and costs around 1/3rd the price.

 I do though have a couple of firmware suggestions for Olympus:

  • create an alternate method of setting the in-camera focus limiter – entering a distance manually is not easy and takes a lot of trial and error work in estimating distances then testing to see if you are correct – surely an option could be to use the current focus position?
  • make another option for AF area selection – perhaps 25-59 AF points?
  • prevent C-AF Tracking from selecting subjects to track which are outside the AF Limiter range – although I suspect C-AF Tracking has a long way to go before it becomes really useful – I do remember once, this was almost useful on my Panasonic GH-1 if the subject was not moving too fast, but the Olympus cameras seem to lose the subject too easily and too randomly. My tip – don’t use C-AF Tr just use C-AF or if your Olympus cameras does not have PDAF, stick to S-AF.
  • add an AF adjustment distance option +/- x meters for scenarios such as the jumps where the camera will AF on the skis leaving the face a touch soft being perhaps 1-2m behind the skis – the ability to program in such fine control could come in handy although only for defined and consistent scenarios with shallow DOF. This would be similar to AF Micro Adjustment function but with a distance scale with 0.1m precision.
  • provide a delete option that deletes the image from both SD cards simultaneously, in a similar way the option to delete RAW and the JPEG on the one card is available.

Tips for using the new unique AF Limiter functionality:

One must set the AF Limiter range in meters via the menu system.

Although you could guess a focus range to use such as 10m to 50m and then test it to ensure your subjects will be able to have AF lock achieved.

There is a much more accurate way – use the other novel functionality – use the Preset MF mode to measure the distances accurately for you!

Set AF mode to PreMF and while in the settings mode, press INFO button, and then half-press shutter to lock AF on various distances, and for each, you will get a read out of the camera to subject distance with 0.1m precision – just what you need when shooting in an aquarium and you wish to ignore the dirt on the glass!

Put your AF mode back to C-AF.

Use the distances to dial into the AF Limiter menu settings (you can store up to 3 AF Limiter ranges).

To rapidly disable the in-camera AF Limiter (eg. you decide to shoot something different), you have several mechanisms:

  • turn it off in the menu – a little time consuming, or,
  • turn the lens focus limiter ON and this will over-ride the in-camera AF Limiter range, or,
  • set your sports shooting mode with AF Limiter ON to a custom setting, and normal mode with AF Limiter OFF to another custom setting, then you can just rotate the PASM dial to switch modes, or,
  • allocate AF Limiter to a function button which will allow you to choose which AF Limiter setting to use or to turn it off


The world is full of millisecond events which all blur in our minds, or we just don’t notice, or perhaps just have an overall gestalt perception – this Olympus camera’s 18fps and 60 fps modes opens up this world – I never really noticed the skier losing grip of the rope during the somersault, my mind barely could take in the somersault itself as it was over and done with so quickly – but this camera caught that moment in time – you just have to be there and be ready – and with pro Capture mode you can even capture the milliseconds before you pressed the button – just awesome!

C-AF is finally there and works extremely well even at 18fps – I am impressed!

Auto focus, Micro Four Thirds cameras, the new Fuji hybrid AF system and the future

Friday, August 6th, 2010

The Micro Four Thirds camera system, along with other mirror-less camera systems are  currently solely reliant on contrast detect autofocus systems.

Contrast Detect AF (CDAF):

Contrast Detect AF relies on assessment of the image contrast at the sensor and then uses a series of iterations of lens element movements so that it can reassess the level of contrast and determine the point of maximum contrast.

The capability of this mechanism to achieve fast AF is limited by the weight of the lens elements involved in focus, the AF motors, the data communication band width between the camera and lens, the AF computer algorithms, subject contrast and movement.

At present technology, even with Panasonic adding 2 extra lens coupling pins for the Micro Four Thirds standard and developing smaller lenses optimised for CDAF, while the AF is very fast for slow moving or stationary subjects, even in low light, even with this optimisation, it has great trouble locking onto faster moving subjects, and thus has limited applicability to sports photography.

When using non-CDAF optimised lenses, AF can be VERY slow, if it works at all (generally will not work on Panasonic GH-1, G1, GF-1 models but will work slowly on later Panasonic models or on Olympus models).

CDAF does have a number of significant advantages over phase contrast AF such as:

  • allows almost any area of the image to be the AF point instead of specified AF sensor sites
  • works even at small apertures as long as there is enough light coming in
  • allows face recognition AF
  • allows AF tracking of slow moving subjects of a specified appearance just by selecting a subject to lock onto
  • eradicates the perennial problem of AF calibration errors

Phase contrast autofocus:

All current dSLRs use phase contrast AF sensors as the primary mechanism.

The AF sensors are generally located under the SLR mirror and some light passes through the mirror then through light splitting prisms to reach the bank of AF sensors.

The light is split so that each sensor detects only light coming from one side of the lens.

Basic AF sensors detect the lateral displacement of a vertical line in the image when the image is out of focus, with the line being displaced to opposite sides of centre depending on which side of the lens the light is coming from.

The camera computer can then use this information of lateral displacement to accurately determine the correct position of the lens focus element required in order to achieve focus.

This makes AF very fast and even predictive continuous AF is fast and can be quite accurate.

Unfortunately, if there is no vertical line, such as sensor will not function, and thus most newer and more expensive dSLRs use AF sensor with horizontal and vertical capabilities (“cross hair” sensors) which increase the chance that it will be able to use part of the subject to AF upon.

As the distance from the lens to the sensor is potentially different to the  distance from the lens to the imaging sensor, there is a potential that different lenses, different temperatures, etc can result in minute changes to these distances and thus the potential for consistent back-focusing or front-focusing to occur which requires AF calibration to correct. Fortunately this is now possible by the end user with newer camera models – previously you would need to send the camera and lens to the manufacturer for calibration.

Another problem is that due to cost issues, generally only the centre AF sensor is made sensitive enough to allow lens apertures up to f/8 while other AF sensors may only work at wider apertures.

This means that if you try to use a 2x teleconverter with an f/5.6 lens, phase contrast will NOT work.

Hybrid AF systems:


Most dSLRs made in the last few years have “Live Preview” mode in which the mirror is temporarily raised and light hits the sensor directly, thus bypassing the phase contrast AF sensors, and thus CDAF must be used. Unfortunately, these systems are not generally optimised for CDAF and thus AF in live preview is quite slow.

A handful of cameras allow phase contrast AF during Live Preview whilst having the mirror in the normal down position by having a separate image sensor in the pentamirror compartment which sends the video feed to the LCD screen. This was first seen in the Olympus E330, and has since been taken up by Sony in some of its models.

Mirror-less camera systems:

Fuji has just announced a new “hybrid AF” technology which essentially converts strips of image sensor photosites into phase contrast AF sensors.

See dpreview’s description of how this works.

This is an exciting development which may allow cameras like the Micro Four Thirds to have fast and accurate action AF without having to worry about mirrors, and then perhaps we will see the development of very fast burst rates of much more than 10fps as there is no physical limitations of moving the mirror up and down.

Olympus is taking their time in developing their new Four Thirds dSLR and this is rumoured to be quite different to previous models and likely to allow both fast CDAF and phase contrast AF – and perhaps optimised for either Micro Four Thirds or Four Thirds lenses – perhaps we will see something in the next few months.

Creating AF lenses from legacy manual focus lenses:

As mentioned in a previous post here, Olympus appears to be working on a new Olympus OM adapter for Micro Four Thirds which not only includes a 0.5x wide converter to give the natural field of view of these lenses but which would also allow fast CDAF.

Also, as mentioned in this post, Panasonic appear to be working on an adapter which includes a pellicle mirror and phase contrast AF sensors which would allow phase contrast AF with Four Thirds lenses and perhaps other legacy lenses when mounted on Micro Four Thirds.

Now these would be a very exciting developments indeed!.

Whatever happens, the improving sensor technology along with improving AF technology will only make the Micro Four Thirds cameras even more compelling as THE camera to take with you every where.

Autofocus and auto metering – some things to consider to get better results

Thursday, November 5th, 2009

Most novice photographers set their camera to the default AF and metering modes, and for the majority of their photos, this probably works good enough for them.

But what happens when you want to compose your subject aesthetically instead of having them in the centre of your frame?

The larger the sensor in the camera, the less depth of field you potentially have, and the more precise your focus needs to be – the problems are many, but one of them is that depending on how you choose to focus, your camera’s exposure system may give quite variable results.

If you have a Panasonic GH-1 or other Micro Four Thirds camera set to face recognition AF and it will AF on your subject’s face, then all is probably well because the camera will meter for the face no matter where the face is in your scene.

The problem is quite different if you use an AF method other than face recognition, or you are using a dSLR such as a Nikon, Canon, Sony, Pentax, or Olympus though.

Let’s first look at focusing assuming you do not have face recognition AF available:

If you have a camera with lots of AF points and you have the patience and can remember how to do it, you could set one of the AF points to the position of your subject within the frame. If you do this, then your camera has a reasonable chance of giving you good focus and metering if your camera’s metering mode is set to Evaluative or Matrix Metering.

However, my preferred AF method for relatively stationary subjects (ie. not in continuous AF action mode) is to ONLY use the centre AF point and have a AFL or Function button on the rear of the camera set to autofocus lock.

This allows me to lock the AF by moving the camera so the centre AF is on my subject and pressing the AFL or Function button, and then I can recompose, wait for the moment I want to capture it without having to keep the shutter half pressed (which results in accidental shots and finger fatigue, particularly with a heavy camera kit), then take the shot.

HOWEVER, there is one big problem with this technique – and that is the camera’s metering.

Most cameras have a sophisticated Evaluative, Multi-Zone or Matrix Metering which breaks the scene into many zones, provides emphasis on the selected AF point(s), looks up a database of many thousands of images, then via a secret algorithm determines the exposure with the aim of converting your subject into a mid-grey tone.

Now this should ring alarm bells – firstly, what if your subject is a white stallion – you don’t want it looking a muddy grey tone, so no matter what metering system you use – you will have to make some exposure compensation to adjust this, or use manual metering. This also applies to people, metering on dark skin will give ~1 stop over-exposure, while metering on light skin will give ~1 stop under-exposure.

BUT, the other alarm bell that is not so obvious, is that it will give priority to the selected AF point – all very well if the AF point is aimed at your subject, but will give extremely variable results if you have focus locked (or use MF and the centre AF point is used by default for metering) and recomposed because the selected AF point may be aimed at a very bright or dark element in the scene which will obviously result in under or over exposure.

One solution to this is to set the AFL button to do AFL and AEL concurrently, but this then does not allow for changes in ambient lighting such as a cloud coming over, and there are individual camera implementation issues.

  • Canon 1D mark III implementation:
    • AF-ON button itself cannot be programmed to also lock exposure, you must also press the AEL button (the asterisk button) but you must also set the desired C.Fn IV setting – the options are:
    • Custom Function IV-1 = 0 results in half-press shutter over-riding AFL – not what we want!
    • Custom Function IV-1 = 1 results in deactivating AF-ON button and thus no AFL – not what we want!
    • Custom Function IV-1 = 2 results in half-press shutter deactivated – what we would like but you must go back into menu system to re-enactivate half-press shutter functionality
    • Custom Function IV-1 = 3 results in half-press shutter over-riding AEL – not what we want!
    • Custom Function IV-1 = 4 results in deactivating AF-ON button and thus no AFL – not what we want!
    • unfortunately this camera does not allow you to disable either the acquired AFL or AEL and resort to half-press shutter by just hitting the AF-ON or AEL button a 2nd time as you can with the Panasonic GH-1
    • and worse, once you have acquired AEL, it becomes deactivated if you try to adjust exposure compensation and even worse, you lose the AEL (along with viewfinder information) after about 6 secs of no activity unless you keep your shutter half-pressed
    • a pretty lame implementation of such an important function, but then Canon’s implementation of other functions such as mirror lock up are just as lame
  • Olympus E-510 implementation:
    • my preferred setting is to set focus mode to MF, wrench menu item AEL/AFL to S:1 C:2 M:3 which then means I am forced to use the AFL button to AF while half-press shutter locks exposure.
    • the nice aspect of this setting is that I only need to set focus mode to C-AF and a novice can use the camera as usual – half-press shutter for both AFL and AEL
    • but you can’t use a button to do both AEL and AFL concurrently as you can on the GH-1
    • and unlike the GH-1, you can’t dial in an exposure compensation whilst your finger is on half-press shutter to hold AEL
  • Panasonic GH-1 implementation:
    • this has the easiest to use functionality and by far the best implementation – its awesome!
    • just set C wrench menu item AF/AE Lock to AF/AE and set AF/AE Lock Hold to ON, then you use the AF/AE Lock button as a toggle to lock or unlock, and when unlocked, the half-press shutter button takes over as usual.
    • and, even better, you can rapidly change the exposure compensation using the front wheel AND see the exposure effect in the EVF AND see a live histogram in the EVF all without taking your eye from the camera – fantastic except, be careful you don’t accidentally change the exposure compensation as it is easy to do!
    • of the 3 cameras, the GH-1 is thus the only one you can lock both AF and AE and put the camera down waiting for the right moment, make changes to exposure compensation after locking, see the exposure effect and even better, automatically turn off the EVF while you are waiting, and the EVF will magically come back to life as soon as you put your eye up to it – another nice touch!
    • of course the dynamic range of the MFT and FT sensors is not as good as the larger sensor of the Canon 1DMIII so you have less exposure latitude and thus exposure accuracy is more important, but at least the GH-1 provides you with rapid feedback while you are taking the image – if the histogram is white and part of it is against the far right frame then you will be getting some blown highlights and you may wish to dial in exposure compensation – just brilliant!
    • it also has object focus tracking mode which can be really handy – just half-press shutter with the centre AF markers over the desired subject until AF is achieved, then you can recompose or move in or out from the subject and the GH-1 will re-acquire AF for that subject no matter where in the frame it is, as long as it still matches the initial pattern and is not moving too much. If this is not suitable you just press AFL button to lock a focus and exposure. Very cool indeed.
    • the evaluative metering mode of the GH-1 when not in face recognition or object tracking mode does seem very much centre-weighted so you may need to compensate for this, luckily compensation is simple to do
    • and that’s not all, if you decide to manually focus such as with tilt shift lenses, the MF assist of the Micro Four Thirds cameras (and the GH-1 with its EVF in particular), give the fastest, most accurate manual focus available courtesy of the fact they do not have to put a mirror up to enter live view to do so
    • the GH-1 though is not without its own faults being quirky at times and having a x-sync of only 1/160th sec without ability to over-ride the shutter speed to force 1/300th sec with flash, an AF system not optimised for birds in flight, lack of in-built IS, but the general AF and exposure system implementation is certainly not one of its faults and is fun to use.

The other solution is to turn off the Evaluative or Matrix Metering mode and resort to manual metering – perhaps by putting meter mode into spot meter and exposure mode to manual then adjusting your exposure manually according to the spot meter on your subject prior to recomposing. This gives you the best control but again does not allow for changes in ambient light.

Perhaps this also gives some insights into the variable results one gets with TTL flash and why many pros resort to manual flash exposure for more consistent results.

see also: