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07-23-2012, 08:40 PM   #1
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Olympus OM-D E-M5: Not quite "the world's fastest autofocus", but still very fast

Look at The Imaging Resource's test results for shutter lag and AF performance:

QuoteQuote:
Full Autofocus, Multi-area AF mode
12-50mm kit lens
0.175 second

Time from fully pressing shutter button to image capture, with the lens already at the proper focal distance setting, at medium focal length.
This result is very fast, especially when you consider that this is contrast detection.

--DragonLord

Edit: I've qualified the Olympus "world's fastest autofocus" claim here. Of course, a contrast-detection AF system cannot keep up with a phase-detection AF system when tracking a moving subject, but when you look at this in the context of contrast-detection AF systems, this is an extremely fast result.


Last edited by bwDraco; 07-26-2012 at 06:05 PM.
07-24-2012, 03:50 PM   #2
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07-25-2012, 11:05 AM   #3
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PL25mm/1.4 is even faster...I assume? Anyway my E-M5 is definitely faster than K-X.
07-25-2012, 11:22 AM   #4
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Erf - I'm a little confused here. That's a measure of the time it takes for the camera to register that it is in focus and fire.

In comparison:
Single Point AF on k-5 - 0.104 second
Full 11 point on k-5 - 0.118 second

Single Point AF on D4 - 0.208 second
Full 51 point AF on D4 - 0.254 second

QuoteQuote:
To minimize the effect of different lens' focusing speed, we test AF-active shutter lag with the lens already set to the correct focal distance.


07-25-2012, 11:28 AM   #5
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Make a sensor smaller and a camera will in fact usually focus faster; such is the case with Olympus
07-25-2012, 12:40 PM   #6
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Is this a satirical thread title?
07-25-2012, 06:30 PM   #7
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QuoteOriginally posted by wjjstu Quote
Is this a satirical thread title?
No, it's not.

To clarify, the value given can only be validly compared with other cameras using contrast detection; phase detection often "knows" when the image is in focus and doesn't need to verify focus the way contrast detection does. In any case, 0.175 second lag for contrast detection is extremely fast.

--DragonLord

Last edited by bwDraco; 07-25-2012 at 06:37 PM.
07-25-2012, 06:38 PM   #8
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QuoteOriginally posted by DragonLord Quote
No, it's not.

To clarify, the value given can only be validly compared with other cameras using contrast detection; phase detection often "knows" when the image is in focus and doesn't need to verify focus the way contrast detection does. In any case, 0.175 second lag for contrast detection is extremely fast.

--DragonLord
Oh - that's good info then. Was confused because I didn't know that.

Wonder how the k-30 will fair.

07-25-2012, 11:45 PM   #9
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Sorry DragonLord, but you are wrong...

Look at the Nikon V1 Compact System Camera Performance - Review

QuoteQuote:
Full Autofocus, Single-point AF mode
0.097 second
Time from fully pressing shutter button to image capture, with the lens already at the proper focal distance setting. (All AF timing performed with the new Nikon 1 10-30mm kit lens.)

And now the OMD...

QuoteQuote:
Full Autofocus, Center AF mode
12-50mm kit lens
0.277 second
According to the same website the Nikon 1 is almost > 3X faster < than the OMD

And while the OMD is marginally faster than the Nikon 1 when it comes to Auto-area / Multi-area mode, bear in mind that the Nikon 1 has almost 4X more focus points which would require more time to process, but would also most certainly result in more accurate focus.

Last edited by JHD; 07-25-2012 at 11:53 PM.
07-26-2012, 01:33 AM   #10
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QuoteOriginally posted by JHD Quote
4X more focus points which would require more time to process, but would also most certainly result in more accurate focus.
You have no idea what are talking about.
Facts:
1) CDAF doesn't have any concept of focus points, it works until some contrast measure will achieve the maximum (today they uses shortcuts as well in order to minimize focus hunting and computations). Due to its nature CDAF is the most accurate method. It also benefits from some sort of scene and pattern recognition.
2) PDAF uses fixed placed sensors, so we only have "focus points" with this method. With this approach we can determine we either have back or front focus at the moment as well as defocus estimation which can be translated into the approximate defocus distance (some sort of indication). You see this method can't be particularly accurate, because it greatly depends on lens and sensor alignment. It also has no idea about the scene (although advanced DSLRs use their metering sensors for scene estimation, but this is quite an expensive approach, both cost and power consumption wise). This method is faster to nail approximate focus since it excludes hunting at all.

The conclusion is Nikon 1 focus points won't bring anything to get more accurate focus. Instead, they help to nail it faster. Hunting is still in final stage when CDAF in action, but the amount of this is quite negligible.

PS There are some new researches that tries to perform approximate focus estimation (i.e. to get focus direction and approximate defocus distance). This problem cannot be resolved with high precision due the nature of model they uses: I'=A*I, where the I is the properly focused image we want to get, I' is the image we have at the moment, the A is so called "spatial convolution" operator, which is also called "S-transform" and represents lens caused blur. Unfortunatelly, the A cannot be reversed otherwise the problem will be quite trivial (if the A would be reversible we will be able to recover missed focus as well during PP, in this case focusing algorithm would act like virtual CDAF). They are trying to make defocus assumptions based on image recognition technics and S-transform properties. They have quite succeeded already, but this isn't production ready yet, since it needs high amount of computations.

Last edited by Emacs; 07-26-2012 at 03:57 AM.
07-26-2012, 03:21 AM   #11
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QuoteOriginally posted by JHD Quote
Sorry DragonLord, but you are wrong...

Look at the Nikon V1 Compact System Camera Performance - Review




And now the OMD...



According to the same website the Nikon 1 is almost > 3X faster < than the OMD

And while the OMD is marginally faster than the Nikon 1 when it comes to Auto-area / Multi-area mode, bear in mind that the Nikon 1 has almost 4X more focus points which would require more time to process, but would also most certainly result in more accurate focus.
The smaller the sensor, the easier a time the camera will have auto focusing, or should anyway. I understand that you really like the Nikon 1 series. It is still a different kettle of fish from an APS-C or four thirds camera and there is a lot more in focus, on average, than with either of those formats. I think the the Olympus OM-D is pretty impressive and truthfully, they have an array of lenses that makes it look like a worthwhile camera system, unlike fairly undeveloped systems like the Nikon 1 series, Pentax Q and even the Sony NEX.
07-26-2012, 06:25 AM - 1 Like   #12
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Olympus AF is indeed fast enough for all AF.S applications now. It feels very snappy.

However, it still doesn't compete well with AF.C. The only useful comparison I am aware of is the Labo FNAC test of the approaching 50 km/h car shot with 35-mm equivalent of 200mm focal length -- and observing at which distance it is loosing track ( http://multimedia.fnac.com/multimedia/editorial/labo/reflex_ete_2012.pdf ).

While most capable cameras fail around 10m (K-5, Alpha 57, D7000, 1100D etc.) and better cameras can go down to 7-8m (D800, D4, 5DmkIII) or less, the only contrast AF camera which can compete is Nikon 1. The Olympus E-M5 failed in that test (23m, I assume that the fast burst and focussing at the same time causes trouble) but other Olympus, like NEX and Panasonic, go up to typically ~15m. Note that there is a singularity at 0m, i.e., 5m means a 3x faster system than 15m.
07-26-2012, 07:21 AM   #13
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QuoteOriginally posted by falconeye Quote
Olympus AF is indeed fast enough for all AF.S applications now. It feels very snappy.
Fast enough and "World's fastest..." are two different realities.

Falk, thanks for you added input.
07-26-2012, 07:50 AM   #14
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QuoteOriginally posted by JHD Quote
Fast enough and "World's fastest..." are two different realities.
The claim of the world's fastest is certainly wrong and this is what Olympus said when launching the camera:
QuoteQuote:
The world’s fastest*2 autofocusing system (FAST AF)
*2 As of November 2011. Among interchangeable-lens digital cameras on the market, and using Olympus’ in-house test conditions.
And they never published those "in-house test conditions". Interestingly nobody ever sued them for that Esp. as Olympus has a tradition to make such unverifiable claims.

So, while not actually the world's fastest, it is indeed fast enough for AF.S.
07-26-2012, 08:22 AM   #15
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QuoteOriginally posted by falconeye Quote
shot with 35-mm equivalent of 200mm focal length
Lens choice has a big impact on µ4/3 focusing speed. I looked at the linked article and didn't see any indicate of what lens was used in the 200mm equivalent test, though I don't speak Frog. Without an indication of what lens was used you can't really say much about the speed of the system. I'm not saying their results are bad, but instead their results are similar to Olympus in being unverifiable.

I've noticed that longer lenses don't focus as quickly with CDAF. I think people have noticed that too with the K-01, but I don't have a link. It may also be that the test is doubly difficult for µ4/3. I've seen other E-M5 users say that C-AF works fine with fast lenses. I don't use C-AF so I wouldn't know. But my point is that by using the worst (long) range with C-AF may not be the best way to characterize E-M5 C-AF in general. I'll freely admit that 200mm equivalent C-AF on the E-M5 probably isn't very good, but the mode isn't useless. I think C-AF might be useful under 100mm equivalent focal length with a faster lens.
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