How is the OMD so fast

Started Jan 7, 2013 | Discussions
zenpmd
Contributing MemberPosts: 765Gear list
Like?
How is the OMD so fast
Jan 7, 2013

So Sony have introduced changes to their sensor, incorporating hybrid phase detection. It looks like Fuji are about to do the same in the updated x100s. But in either case they aren't/won't be as quick as the OMD.

How does OMD achieve the speed it does? What is the technology behind it?

 zenpmd's gear list:zenpmd's gear list
Canon EOS 5D Mark III Canon EF 70-200mm f/2.8L IS II USM Canon EF 24-70mm f/2.8L II USM Canon EF 35mm f/2 IS USM
Fujifilm X100S
If you believe there are incorrect tags, please send us this post using our feedback form.
papillon_65
Forum ProPosts: 17,958Gear list
Like?
Re: How is the OMD so fast
In reply to zenpmd, Jan 7, 2013

zenpmd wrote:

So Sony have introduced changes to their sensor, incorporating hybrid phase detection. It looks like Fuji are about to do the same in the updated x100s. But in either case they aren't/won't be as quick as the OMD.

How does OMD achieve the speed it does? What is the technology behind it?

I would assume that it's a simple case of more horsepower under the bonnet. The speed of AF is related to how fast the processor can compute the data and move the lens elements. The OMD has been criticised for it's price, but alongside the 5 axis IBIS and the fast AF then part of that price has to be related to the chip and computing power of the camera, which after all is a computer with a sensor and lens attached. I don't think there is any special Olympus magic going on, I just think they have used good quality processors in this camera.

-- hide signature --

Any problem on earth can be solved by a well aimed Pomegranate...
Tony
http://the-random-photographer.blogspot.com/

 papillon_65's gear list:papillon_65's gear list
Sigma DP1 Merrill Sigma DP2 Merrill Fujifilm XF1 Fujifilm X-T1 Fujifilm XF 18-55mm F2.8-4 R LM OIS +2 more
Reply   Reply with quote   Complain
zenpmd
Contributing MemberPosts: 765Gear list
Like?
Re: How is the OMD so fast
In reply to papillon_65, Jan 7, 2013

Does it have phase detection on the sensor or is it purely a contrast system?

The heart of this question is to see if it is an inevitability that the Nex and Fuji systems will quickly catch up.

 zenpmd's gear list:zenpmd's gear list
Canon EOS 5D Mark III Canon EF 70-200mm f/2.8L IS II USM Canon EF 24-70mm f/2.8L II USM Canon EF 35mm f/2 IS USM
Reply   Reply with quote   Complain
Steve_
Senior MemberPosts: 2,035Gear list
Like?
Pentax still hasn't caught up with PDAF
In reply to zenpmd, Jan 7, 2013

There's no guarantee that Fuji will ever figure things out.

OMD is purely CDAF.

 Steve_'s gear list:Steve_'s gear list
Olympus OM-D E-M5 Panasonic Lumix G Vario 7-14mm F4 ASPH Panasonic Lumix G 14mm F2.5 ASPH Panasonic Leica Summilux DG 25mm F1.4 Olympus M.Zuiko Digital 45mm 1:1.8 +6 more
Reply   Reply with quote   Complain
papillon_65
Forum ProPosts: 17,958Gear list
Like?
Re: How is the OMD so fast
In reply to zenpmd, Jan 7, 2013

zenpmd wrote:

Does it have phase detection on the sensor or is it purely a contrast system?

The heart of this question is to see if it is an inevitability that the Nex and Fuji systems will quickly catch up.

It is CDAF only because all m4/3's lenses are designed for CDAF focusing. Combining CDAF and PDAF on a sensor is a kludge which means that you are forced to use larger lenses which are designed for PDAF. The only disadvantage of CDAF focusing is the current state of play with regards to C-AF focusing. I believe that CDAF systems will overcome this with time though it doesn't bother me personally. So while other systems will enable you to use pdaf you lose the size advantage of the smaller lenses, so why not just use a DSLR instead?
CDAF lenses need to be smaller and lighter because of the movement of the lens elements required in the shuffling process while they obtain focus. The main advantage of CDAF focusing is the accuracy of focusing. They're either bang on or they sometimes pick the background out if you are using a large sized focusing box. On the OMD I haven't found this to be a problem as the smallest focus box is small enough to avoid this. PDAF focusing can be problematical on plenty of lenses and is not as reliable in my experience. On many cameras you need to calibrate your pdaf lenses individually, not great for me personally. There are thousands of threads on lens calibration on PDAF systems on DPR alone. With the OMD I have found that the focusing is totally reliable and accurate, that works for me.

-- hide signature --

Any problem on earth can be solved by a well aimed Pomegranate...
Tony
http://the-random-photographer.blogspot.com/

 papillon_65's gear list:papillon_65's gear list
Sigma DP1 Merrill Sigma DP2 Merrill Fujifilm XF1 Fujifilm X-T1 Fujifilm XF 18-55mm F2.8-4 R LM OIS +2 more
Reply   Reply with quote   Complain
rrr_hhh
Veteran MemberPosts: 5,919Gear list
Like?
Re: How is the OMD so fast
In reply to zenpmd, Jan 7, 2013

zenpmd wrote:

Does it have phase detection on the sensor or is it purely a contrast system?

The heart of this question is to see if it is an inevitability that the Nex and Fuji systems will quickly catch up.

It is purely CDAF, no hybrid system. This is why CAF and especially CAF + tracking isn't as good as in a DSLRs.   and also why the mft cameras can't focus older FT lenses, which were designed for PDAF, at the same speed. AF speed s gained both from the body (powerful prcessor) and the lens (lighter elements to move in shorter distances and other design concept  : no helicoid, focus by wire instead of mechanically).

-- hide signature --

rrr_hhh

Reply   Reply with quote   Complain
Gottschalk
Senior MemberPosts: 1,243
Like?
Re: How is the OMD so fast
In reply to zenpmd, Jan 7, 2013

I believe Olympus reads the AF info out of the sensor at 120 times a second, and has a CPU that can compute this info as well. Couple that with a lens that's optimised with fast AF and you get very fast AF.

-- hide signature --

It's not the size of your sensor but how you use it that counts...

Reply   Reply with quote   Complain
zenpmd
Contributing MemberPosts: 765Gear list
Like?
Re: How is the OMD so fast
In reply to Gottschalk, Jan 7, 2013

Thanks everyone. Interesting.

It looks like contrast detection is a good system then - I am sure one day they will figure out how to track. And its a definate plus having a smaller lens. But that can't be all the picture - since Pentax have phase detection systems with tiny but world class primes?

 zenpmd's gear list:zenpmd's gear list
Canon EOS 5D Mark III Canon EF 70-200mm f/2.8L IS II USM Canon EF 24-70mm f/2.8L II USM Canon EF 35mm f/2 IS USM
Reply   Reply with quote   Complain
Paul De Bra
Forum ProPosts: 11,278Gear list
Like?
Good tracking requires PDAF.
In reply to zenpmd, Jan 7, 2013

Your expectation that CDAF will somehow be able to track in the future is somewhat unrealistic. The fundamental difference in property is that with CDAF when a subject goes out of focus the image does not have any information whether the subject is coming closer or moving further away. This could be done with clever motion analysis but from a single image captured by the sensor you cannot know this. With PDAF when a subject goes out of focus the sensor can detect whether it is out of focus because the subject is too close or because it is too far away. It works like with the "two halves" in older MF dslrs: the two halves of the focus point move away in one way when you focus closer and the other way when you focus further away, and with PDAF this info is used. So PDAF knows in which direction focus needs to be adjusted and CDAF does not know and has to try one way and if the image becomes more blurred then try the other way... The info for selecting the right direction just isn't there in the image. An image sequence is needed and clever processing to detect the direction of motion. We need a serious gain in on-board processing power to achieve that.

-- hide signature --

Slowly learning to use the Olympus OM-D E-M5.
Public pictures at http://debra.zenfolio.com/.

 Paul De Bra's gear list:Paul De Bra's gear list
Fujifilm FinePix F200EXR Olympus OM-D E-M5 Olympus M.Zuiko Digital ED 9-18mm 1:4.0-5.6 Panasonic Lumix G 20mm F1.7 ASPH Olympus M.Zuiko Digital ED 75-300mm 1:4.8-6.7 +4 more
Reply   Reply with quote   Complain
sgoldswo
Senior MemberPosts: 3,532Gear list
Like?
Re: Good tracking requires PDAF.
In reply to Paul De Bra, Jan 7, 2013

Paul De Bra wrote:

Your expectation that CDAF will somehow be able to track in the future is somewhat unrealistic. The fundamental difference in property is that with CDAF when a subject goes out of focus the image does not have any information whether the subject is coming closer or moving further away. This could be done with clever motion analysis but from a single image captured by the sensor you cannot know this. With PDAF when a subject goes out of focus the sensor can detect whether it is out of focus because the subject is too close or because it is too far away. It works like with the "two halves" in older MF dslrs: the two halves of the focus point move away in one way when you focus closer and the other way when you focus further away, and with PDAF this info is used. So PDAF knows in which direction focus needs to be adjusted and CDAF does not know and has to try one way and if the image becomes more blurred then try the other way... The info for selecting the right direction just isn't there in the image. An image sequence is needed and clever processing to detect the direction of motion. We need a serious gain in on-board processing power to achieve that.

-- hide signature --

Slowly learning to use the Olympus OM-D E-M5.
Public pictures at http://debra.zenfolio.com/.

And yet the GH3 (CDAF only) CAF, though not perfect, is an incremental improvement on the E-M5 in this regard. It seems about as good as an entry level DSLR (which admittedly won't have the best PDAF in the world).

 sgoldswo's gear list:sgoldswo's gear list
Leica M Typ 240 Olympus E-M1 Nikon Df Nikon D810
Reply   Reply with quote   Complain
AndyGM
Contributing MemberPosts: 695Gear list
Like?
Re: How is the OMD so fast
In reply to papillon_65, Jan 7, 2013

papillon_65 wrote:

It is CDAF only because all m4/3's lenses are designed for CDAF focusing. Combining CDAF and PDAF on a sensor is a kludge which means that you are forced to use larger lenses which are designed for PDAF.

Well, you are not forced to use large lenses when combining PDAF and CDAF, that is incorrect. With a hybrid system, CDAF is still used for part of the focusing (usually for a final accuracy check) so everything you say about small lens elements that have to be able to move back and forth fast still applies. PDAF does not mean big lenses, look at the Nikon 1 system. Should an m43 camera get hybrid PDAF/CDAF in the future, the existing small CDAF optimised m43 lenses should still work with it, so the ability to track subjects moving toward or away with continuous AF should improve for the m43 system as a whole.

The other advantage is the camera can switch to a PDAF only mode when used with adapted lenses that were only designed for PDAF, like the Four Thirds system lenses. The intention of doing this is not to stop m43 lens development because we will be expected to just use the larger Four Thirds lenses that already exist. The intention is to give existing Four Thirds camera body owners an upgrade path where they can continue to use the Four Thirds lenses they already have (and that were usually bought at great expense).

I believe that CDAF systems will overcome this with time though it doesn't bother me personally. So while other systems will enable you to use pdaf you lose the size advantage of the smaller lenses, so why not just use a DSLR instead?

I really don't think this issue of at least knowing if the subject is moving toward or away is ever going to be overcome with CDAF, as Paul has explained in a later post. Hybrid CDAF/PDAF for m43 is therefore not a kludge, its an inevitability.

 AndyGM's gear list:AndyGM's gear list
Olympus PEN E-PL1 Olympus PEN E-PL3 Panasonic Lumix G 20mm F1.7 ASPH Olympus M.Zuiko Digital ED 14-150mm 1:4-5.6 Olympus M.Zuiko Digital 14-42mm 1:3.5-5.6 II R +1 more
Reply   Reply with quote   Complain
papillon_65
Forum ProPosts: 17,958Gear list
Like?
Re: How is the OMD so fast
In reply to AndyGM, Jan 7, 2013

AndyGM wrote:

papillon_65 wrote:

It is CDAF only because all m4/3's lenses are designed for CDAF focusing. Combining CDAF and PDAF on a sensor is a kludge which means that you are forced to use larger lenses which are designed for PDAF.

Well, you are not forced to use large lenses when combining PDAF and CDAF, that is incorrect. With a hybrid system, CDAF is still used for part of the focusing (usually for a final accuracy check) so everything you say about small lens elements that have to be able to move back and forth fast still applies. PDAF does not mean big lenses, look at the Nikon 1 system. Should an m43 camera get hybrid PDAF/CDAF in the future, the existing small CDAF optimised m43 lenses should still work with it, so the ability to track subjects moving toward or away with continuous AF should improve for the m43 system as a whole.

You are if you want to use a fast longer telephoto lenses, because these will invariably be large due to the amount of glass required. Unless optical design changes it's unlikely you will ever see a small  fast sports lens with decent reach that will use CDAF focusing. The 35-100mm F2.8 is about as good as it's going to get for a small camera unless you use a larger camera body. You're then into GH3 territory and you may as well use a DSLR IMHO.

The other advantage is the camera can switch to a PDAF only mode when used with adapted lenses that were only designed for PDAF, like the Four Thirds system lenses. The intention of doing this is not to stop m43 lens development because we will be expected to just use the larger Four Thirds lenses that already exist. The intention is to give existing Four Thirds camera body owners an upgrade path where they can continue to use the Four Thirds lenses they already have (and that were usually bought at great expense).

Lenses like the 12-60mm and 50-200mm are just too large to be used comfortably on a camera like the OMD, I know, I've tried it. Even with PDAF speed focusing I wouldn't want to use these lenses on m4/3's. This system is all about size reduction for most people.

I believe that CDAF systems will overcome this with time though it doesn't bother me personally. So while other systems will enable you to use pdaf you lose the size advantage of the smaller lenses, so why not just use a DSLR instead?

I really don't think this issue of at least knowing if the subject is moving toward or away is ever going to be overcome with CDAF, as Paul has explained in a later post. Hybrid CDAF/PDAF for m43 is therefore not a kludge, its an inevitability.

If you have to choose between two different focusing systems to achieve the same thing it's a kludge in my book. The ideal focusing system would do it all on an m4/3's sized or similar camera.

-- hide signature --

Any problem on earth can be solved by a well aimed Pomegranate...
Tony
http://the-random-photographer.blogspot.com/

 papillon_65's gear list:papillon_65's gear list
Sigma DP1 Merrill Sigma DP2 Merrill Fujifilm XF1 Fujifilm X-T1 Fujifilm XF 18-55mm F2.8-4 R LM OIS +2 more
Reply   Reply with quote   Complain
zenpmd
Contributing MemberPosts: 765Gear list
Like?
Re: How is the OMD so fast
In reply to papillon_65, Jan 7, 2013

If what everyone is saying is true, then it is unfair and even stupid that teh dpreview criticises the OMD-E5 for poor tracking autofocus - it cannot help it.

Why, then, however, are mirrorless devices on just phase detection?

 zenpmd's gear list:zenpmd's gear list
Canon EOS 5D Mark III Canon EF 70-200mm f/2.8L IS II USM Canon EF 24-70mm f/2.8L II USM Canon EF 35mm f/2 IS USM
Reply   Reply with quote   Complain
CharlesTokyo
Contributing MemberPosts: 704Gear list
Like?
Re: How is the OMD so fast
In reply to AndyGM, Jan 7, 2013

AndyGM wrote:

papillon_65 wrote:

It is CDAF only because all m4/3's lenses are designed for CDAF focusing. Combining CDAF and PDAF on a sensor is a kludge which means that you are forced to use larger lenses which are designed for PDAF.

Well, you are not forced to use large lenses when combining PDAF and CDAF, that is incorrect. With a hybrid system, CDAF is still used for part of the focusing (usually for a final accuracy check) so everything you say about small lens elements that have to be able to move back and forth fast still applies. PDAF does not mean big lenses, look at the Nikon 1 system. Should an m43 camera get hybrid PDAF/CDAF in the future, the existing small CDAF optimised m43 lenses should still work with it, so the ability to track subjects moving toward or away with continuous AF should improve for the m43 system as a whole.

Are you sure about CDAF being used for part of the focusing? Maybe on some systems, but I doubt all of them. Although the interaction with the hardware is important, as is the sensor readout CDAF is software based and can use all of the data the sensor has (at least as much as it reads out when focusing) It will improve as algorithms and processing power increase and it's quite possible it's tracking will be better than PDAF in the long term because of the extra data it has available. When using CAF normally the distance moved may be small, and possibly more in the area of CDAF than PDAF.

The other advantage is the camera can switch to a PDAF only mode when used with adapted lenses that were only designed for PDAF, like the Four Thirds system lenses. The intention of doing this is not to stop m43 lens development because we will be expected to just use the larger Four Thirds lenses that already exist. The intention is to give existing Four Thirds camera body owners an upgrade path where they can continue to use the Four Thirds lenses they already have (and that were usually bought at great expense).

Yes, if you use use PDAF lenses. It's attractive at the moment because of the high quality lenses, but the size certainly doesn't appeal to m43s users. PDAF is also inherently less precise then CDAF. CDAF tends to cluster more closely where PDAF can sometimes be off quite a way. CDAF (assuming a proper focusing point size, against probably a processing issue) is more accurate and doesn't suffer from front and back focusing problems that PDAF does. I'm not eager to see m43s adapt PDAF and I have to go back to calibrating all my lenses again.

If very well may be they use PDAF to allow use of older lenses in a new 43s or hybrid body, but I'm not sure I'd call it a step forward.

I believe that CDAF systems will overcome this with time though it doesn't bother me personally. So while other systems will enable you to use pdaf you lose the size advantage of the smaller lenses, so why not just use a DSLR instead?

I really don't think this issue of at least knowing if the subject is moving toward or away is ever going to be overcome with CDAF, as Paul has explained in a later post. Hybrid CDAF/PDAF for m43 is therefore not a kludge, its an inevitability.

Yes, it may not be an easy solution, but I do see them over coming it. I don't see m43s ever going to a hybrid solution with PDAF for m43s lenses and I'd gamble that other mirror systems will move strictly to CDAF over time as other companies catch up.

 CharlesTokyo's gear list:CharlesTokyo's gear list
Ricoh GR Panasonic Lumix DMC-GF1 Olympus OM-D E-M5 Olympus E-M1 Olympus M.Zuiko Digital ED 9-18mm 1:4.0-5.6 +22 more
Reply   Reply with quote   Complain
bcalkins
Regular MemberPosts: 339Gear list
Like?
Not necessarily...
In reply to Paul De Bra, Jan 7, 2013

I don't see why CDAF systems can't do tracking as well in the future for stills.  PDAF has an advantage in that it is predictive, but with frame rates of 10fps you just need to get focus right every 100ms.  a CDAF based system would seem to need to 'wobble' to check focus, but if everything else was fast enough it could keep up with a moving subject.  it could also bring with it the advantage of tracking by color anywhere on the sensor.

I would say that adding PDAF to the sensor seems logical since it seems technically easy enough to do, but the only downside of a fast CDAF tracking system is the user experience seeing it go in and out of focus slightly - but that doesn't mean it can't ever keep up with fast moving subjects...  A really clever system in the future with faster chip readout could even hide the wobble by skipping a few frames in the EVF

CDAF has accuracy on its side - and works in both the viewfinder and on the rear screen without a pellicle mirror that adds distance to the lens mount.  It will keep getting better.  There is a big difference between saying PDAF is better NOW, versus saying it will always be better.

 bcalkins's gear list:bcalkins's gear list
Olympus E-M1 Panasonic Leica Summilux DG 25mm F1.4 Olympus Zuiko Digital ED 50mm 1:2.0 Macro Olympus Zuiko Digital ED 50-200mm 1:2.8-3.5 SWD Panasonic Lumix G 14mm F2.5 ASPH +5 more
Reply   Reply with quote   Complain
zenpmd
Contributing MemberPosts: 765Gear list
Like?
Re: How is the OMD so fast
In reply to CharlesTokyo, Jan 7, 2013

CharlesTokyo wrote:

It's attractive at the moment because of the high quality lenses, but the size certainly doesn't appeal to m43s users.

Why do you say this? As above, I refer to Pentax primes as being as thin as pancakes yet optically amazing. Your argument seems to have been invented by proponents of the 4/3 system as a incorrect defence against, say, the Nex system and indeed Fujis.

 zenpmd's gear list:zenpmd's gear list
Canon EOS 5D Mark III Canon EF 70-200mm f/2.8L IS II USM Canon EF 24-70mm f/2.8L II USM Canon EF 35mm f/2 IS USM
Reply   Reply with quote   Complain
OniMirage
Contributing MemberPosts: 990
Like?
Re: How is the OMD so fast
In reply to zenpmd, Jan 7, 2013

I read through most of the posts and there is something everyone is missing. The 4/3 system  when first introduced was created from the ground up. The lenses, all of them, are digital specific so the read out they produce is easily translated by the processors in the cameras. This is different from other system that adapted auto focus into older traditional lens designs. It allowed Panny and Oly to develop much better designs and while many hate the focus by wire type auto focus most of the lenses use we see now that it was a good design decision as it has allowed them to create these insanely fast and accurate focusing systems. They can continue to increase speed and accuracy by simply tweaking the processors, adding a dual core like the OMD, doubling the sample rate like the OMD, it's all very easy, and they can do it again and again.

Reply   Reply with quote   Complain
zenpmd
Contributing MemberPosts: 765Gear list
Like?
Re: How is the OMD so fast
In reply to OniMirage, Jan 7, 2013

What do you mean by focus by wire? As opposed to what

 zenpmd's gear list:zenpmd's gear list
Canon EOS 5D Mark III Canon EF 70-200mm f/2.8L IS II USM Canon EF 24-70mm f/2.8L II USM Canon EF 35mm f/2 IS USM
Reply   Reply with quote   Complain
rrr_hhh
Veteran MemberPosts: 5,919Gear list
Like?
Re: How is the OMD so fast
In reply to zenpmd, Jan 7, 2013

zenpmd wrote:

What do you mean by focus by wire? As opposed to what

It is not fully mechanical with an helicoïd like in the traditional lenses. When you are focusing manually, the focusing ring transmits your movements to the processor and the processor moves the lenses elements forwards or backward. The main point is that you loose the feedback from the lens; there are no end stops either at infinite or nearest focusing distance. On very long lenses, you can spin and spin the focus ring without knowing where you are, whether you are too far away or too near. On shorter lenses this is less of a problem.

In the case of the 20mm Panasonic, the lens elements seem to be activated by a spring, as is shown here . But not all have that type of design. In fact, that 20mm is an older design. How the lens is pushed forward and backward that fast in mft lenses isn't entirely clear to me. For sure the focusing lens elements have to be moved, but how ? They could even use magnets in newer lens designs ? and adjusts the movements electronically ?

Olympus has issued two special lenses (12 and 17mm)  which have a snap focus ring which tries to give you that feedback again and unveils distance scales when you push/pull it (although they aren't very precise), they should allow photographers to use zone focusing like with old legacy lenses. But it is just an improved focus by wire design, not the old mechanical design.

-- hide signature --

rrr_hhh

Reply   Reply with quote   Complain
OniMirage
Contributing MemberPosts: 990
Like?
Re: Good tracking requires PDAF.
In reply to Paul De Bra, Jan 7, 2013

Paul De Bra wrote:

Your expectation that CDAF will somehow be able to track in the future is somewhat unrealistic. The fundamental difference in property is that with CDAF when a subject goes out of focus the image does not have any information whether the subject is coming closer or moving further away. This could be done with clever motion analysis but from a single image captured by the sensor you cannot know this. With PDAF when a subject goes out of focus the sensor can detect whether it is out of focus because the subject is too close or because it is too far away. It works like with the "two halves" in older MF dslrs: the two halves of the focus point move away in one way when you focus closer and the other way when you focus further away, and with PDAF this info is used. So PDAF knows in which direction focus needs to be adjusted and CDAF does not know and has to try one way and if the image becomes more blurred then try the other way... The info for selecting the right direction just isn't there in the image. An image sequence is needed and clever processing to detect the direction of motion. We need a serious gain in on-board processing power to achieve that.

-- hide signature --

Slowly learning to use the Olympus OM-D E-M5.
Public pictures at http://debra.zenfolio.com/.

Both systems are reactive. If the image becomes out of focus the PDAF system may know where to go but it's still lagging by reacting to an out of focus subject. CDAF in its current form unfortunately focuses to infinity and back and doesn't know if the image is getting worse until it comes back the other way. Developers need to find a way to determine if the subject is getting worse by going so far it needs to stop and go the other way. Continuous CDAF actually works this way right now. Alternatively they could do it another way, by using an infrared depth sensor which would be superior to either PDAF or CDAF in tracking capability. Considering the size of the sensor in a m4/3 camera the depth range available would be pretty extreme if they could incorporate that type of system.

Reply   Reply with quote   Complain
Keyboard shortcuts:
FForum MMy threads