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June 21, 2012


"Olympus claims that they have achieved the world’s fastest autofocus speed."

I thought they claimed the worlds fastest mirror-less AF speed. Mirror-less cameras are not known for fast AF, so Olympus's claim may well be true.

AF speed depends on the lens as well as the camera. Small mirror-less cameras like the Olympus OM-D E-M5 have an advantage that they use shorter focal length lens because they have a smaller sensor. The lenses are also smaller because the camera does not have a mirror and the lens can be closer to the sensor. These lens should focus faster. There is less glass to move.

There is a hybrid approach from Sony called Single-Lens Tranlucent (SLT). This has a fixed semi-transparent mirror that deflects 10-20% of the light to a PDAF system located in the pentaprism housing. The viewfinder is a EVF rather than optical.

These camera are bigger than mirror-less cameras, more like a DSLR, but they have a PDAF system that can do AF while taking pictures at high frame rates or shooting video.

Unfortunately, from reading reviews of these cameras, it looks like Sony has not perfected this AF. Nikon and Canon have many years of engineering invested in auto tracking AF systems in their top end cameras (Nikon D4, D800, D7000, Canon 1Dx, 5D3, 7D). Tests indicate the Sony system just isn't competitive with those top end cameras, at least not yet.

Olympus OM-D E-M5 has a continuous AF feature, but DPReview was not very impressed with it. They indicated it sometimes lost the subject.

Canon has just announced a new hybrid AF system in the T4i (650D). This camera has a main sensor that contains pixels dedicated to PDAF. The T4i is a DSLR and also has a conventional PDAF system. The hybrid AF is suppose to be used in liveview or video. The PDAF is used for subject tracking and CDAF is used for final focus. Canon claims PDAF is better for subject tracking. I have not seen any reviews of this yet, so no idea how well it works. There are rumors that Canon is going to enter the mirror-less segment in the next few months. If they do, they will probably use this hybrid AF technology there too.

must be
one helluva
- new camera

What is the delay between the initial click and the photo being taken?

With an DSLR there is virtually no delay.

Every non DSLR camera I have used has a delay on the order of 1/2 a second.

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