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Olympus OM-D E-M1 The first Micro Four Thirds camera that offers phase detect focusing so you can use Four Thirds DSLR lenses normally as well a Micro Four Thirds lenses.

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Old 11th October 2015
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EM1 focusing accuracy?

Same subject, two single frames, same target (shoulder), one second in between frames. Got AF beep confirmation for each frame. SAF single point focus.

E-M1 300/2.8 + EC14, a combination that I don't use often due to the AF issue.
FW 3.1

At a first glance these pictures look good but they are not. Look close and you will see they are sharp nut the first one is suffering from 3-4 cm back-focus and the seecond one is suffering from 2 cm front-focus. That's really bad in my opinion.

I see this happening all the time. It's not a calibration issue. There is nothing wrong with the lens, when coupled with the right body (E5) or used in MF it delivers superb results.

I (and others) have been complaing about the EM1 CAF performance - maybe the issue is about AF accuracy as such?

Am I the only one?




Back focus:


Front focus:
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Old 11th October 2015
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Re: EM1 focusing accuracy?

Nope. I noticed that of distant subjects, (infinity), using the 50-200mm, or 75-300mm I get more accurate focus using C-AF. So much so, I have set up a myset using back button focus and C-AF. In close...30ft or so I have not noticed any problem.
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Old 11th October 2015
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Re: EM1 focusing accuracy?

I found that one of the main issues with small birds is the size of the single point, even the small single point. I certainly noticed this when moving over from the E5 to the E-M5 and subsequently the E-M1. No easy solution I found apart from using a smaller f stop.

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Old 13th October 2015
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Re: EM1 focusing accuracy?

It may not be the Auto focus, I notice your shutter speed was only 1/320s Little birds are constantly jumping around, and I tend to use 1/2000s or so for them.
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Old 13th October 2015
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Re: EM1 focusing accuracy?

Look at the twigs. They are sharp. It's not shake blur but an OOF issue
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Old 13th October 2015
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Re: EM1 focusing accuracy?

Hi Trod, it is a known issue with that lens and a couple of other 4/3rds lenses on m4/33rds bodies. They are not setup for that system, also on contrast detect, they tend to focus on the nearest contrast which is why it hit on the branches, not the robin, which is less contrast.

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Re: EM1 focusing accuracy?

Dave,

I thought the EM1 was using PDAF when coupled with 4/3 lenses. Now I am confused.
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Old 13th October 2015
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Re: EM1 focusing accuracy?

The PDAF of the E-M1 is done on the sensor by shielded pairs of photo sites.

The PDAF on the E-5 is done with dedicated cells within the mirror box.

I believe the E-5 system to be cross type sensors, but the E-M1 is only line type.

This may well be why you experience differences.
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Old 13th October 2015
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Re: EM1 focusing accuracy?

E-M1 is the first Olymus to use on-sensor PDAF,
surely expecting it to be as accurrate (or convenient) as a mature DSLR PDAF is expecting a bit too much,
the E-M1 isn't the holy grail
and Olympus refused to make the hold grail : a DSLR with the new sensors.
Shame.

Hope for better results from the next one maybe?
An E-7/e-700 would have been so great...
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Re: EM1 focusing accuracy?

I suspect the problem is more to do with the lens than the camera.

The 300/2.8 was launched in 2004 and pre-dates things like Liveview, SWD drives and fast microprosessors etc. Both the mechanical and electrical/electronic elements of its internal autofocus system will all be using technology which is inferior to that employed in current lenses. Added to this it is a large lens and the mechanical inertia in it will be considerable. I suspect that the setting accuracy and repeatability of its internal autofocus system when driven by a camera system primarily designed to drive more responsive lens systems will not be optimal.

The fact that optically the lens can focus perfectly in manual mode shows that the human "focus driving system" is more inteligent and can adapt to match the capability of the lens.

Regards.
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Re: EM1 focusing accuracy?

Quote:
Originally Posted by Tordan58 View Post
Dave,

I thought the EM1 was using PDAF when coupled with 4/3 lenses. Now I am confused.
Hi Tord yes the em 1 uses padaf but it is on sensor the 300 f2.8 lens cannot perform to its ability on a system that it was not designed to be used, the padaf system was a get around for lenses that had been optimised for live view. It is a shame Olympus didn't come up with a mod for that great lens so it could perform to its normal accuracy. Maybe the new 300 f4 will be its modern equivalent, only time will tell.
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Old 31st October 2015
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Re: EM1 focusing accuracy?

I had this same issue with a 50-200 SWD which greatly reduced after a lens firmware update. 1.1 was out in 2010 but mine had not been updated in it's earlier life.
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Old 31st October 2015
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Re: EM1 focusing accuracy?

Quote:
Originally Posted by Graham_of_Rainham View Post
The PDAF of the E-M1 is done on the sensor by shielded pairs of photo sites.

The PDAF on the E-5 is done with dedicated cells within the mirror box.

I believe the E-5 system to be cross type sensors, but the E-M1 is only line type.

This may well be why you experience differences.
I would add to that with the bird having mostly horizontal detail in its feathers which would make it more difficult for the PD-AF in the E-M1 to focus on. Had Tord taken the photo of this subject in portrait position I think results would have been better, but the focus area would have to be on the bird only.

The other thing that would make a difference to focus accuracy is speed of focus & any movement of subject. That is, was the tree moving at all with a breeze?
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Old 2nd November 2015
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Re: EM1 focusing accuracy?

Ross, the pictures were taken during a calm day with hardly any wind. I repeated the test the past weekend, using AF-S, one single AF point (small). I was targeting static subjects with distinctive vertical features (twigs and alike) and got a mixed bag of results. Some were correctly focused (and pin sharp), most were a tad OOF. Shame.
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Old 2nd November 2015
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Re: EM1 focusing accuracy?

Quote:
Originally Posted by PeterBirder View Post
I suspect the problem is more to do with the lens than the camera.

The 300/2.8 was launched in 2004 and pre-dates things like Liveview, SWD drives and fast microprosessors etc. Both the mechanical and electrical/electronic elements of its internal autofocus system will all be using technology which is inferior to that employed in current lenses. Added to this it is a large lens and the mechanical inertia in it will be considerable. I suspect that the setting accuracy and repeatability of its internal autofocus system when driven by a camera system primarily designed to drive more responsive lens systems will not be optimal.

The fact that optically the lens can focus perfectly in manual mode shows that the human "focus driving system" is more inteligent and can adapt to match the capability of the lens.

Regards.
Yes the lens will provide perfect results but fine tuning MF with that lens is not easiest of things. It is much easier with the scope Crayford dual speed focuser. I should probably stay away from the EM-1/300 2.8 combination (and stick to the E5 instead). And wish Santa brings us an E7 (which will probably not happen).

In the meantime I hope to be able to borrow and test a Canon 400/5.6 qith metabones MFT-EF adapter with my EM1. I have read this setup provides a great AF accuracy (AF performance is not lightning fast, but very acceptable) and I have seen samples that look promising. These Canon lenses have a solid reputation and the second hand prices have dropped significantly since they lack IS and are not so popular any longer after the 100-400 II has been introduced, and the E-M1 IBIS would come in handy. Stay tuned...
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