focus accuracy testing by Roger Cicala, at Imaging Resource

[BJL]

Roger Cicala (of Lens Rentals) has a pair of interesting articles about focus accuracy over at Imaging Resource:
http://www.imaging-resource.com/news/2012/07/23/autofocus-reality-part-1-center-point-single-shot-accuracy
http://www.imaging-resource.com/news/2012/07/24/autofocus-reality-part-2-one-vs.-two-old-vs.-new

One clear conclusion: for stationary subjects, CDAF overall beats PDAF with greater accuracy and less shot-to-shot variation. With Canon 5D II and III bodies and Canon lenses anyway.

[telyt]

One clear conclusion: for stationary subjects, CDAF overall beats PDAF with greater accuracy and less shot-to-shot variation. With Canon 5D II and III bodies and Canon lenses anyway.

No surprise.  PDAF is rube goldberg technology.  I'm surprised it works as well as it does.

[NancyP]

for stationary subjects, Roger's manual focusing was as good as the CDAF.

[Ellis Vener]

Roger Cicala (of Lens Rentals) has a pair of interesting articles about focus accuracy over at Imaging Resource:
http://www.imaging-resource.com/news/2012/07/23/autofocus-reality-part-1-center-point-single-shot-accuracy
http://www.imaging-resource.com/news/2012/07/24/autofocus-reality-part-2-one-vs.-two-old-vs.-new

One clear conclusion: for stationary subjects, CDAF overall beats PDAF with greater accuracy and less shot-to-shot variation. With Canon 5D II and III bodies and Canon lenses anyway.

I also see this in the new Nikon D800,  D800E and D4 bodies as well

[deejjjaaaa]

for stationary subjects, Roger's manual focusing was as good as the CDAF.

his manual focusing was not through the optical viewfinder though - but using LV, which is essentially just using the human judgement (and human speed of operation) in CDAF to decide where the point of max contrast is... the proper comparison shall be PDAF vs CDAF vs MF using optical viewfinder (w/ MF focusing screen of choice).

PS: but then through optical viewfinder is just using the human judgement (and human speed of operation) in PDAF, same principle  ... so probably both manual focusing techniques shall be included

[telyt]

PS: but then through optical viewfinder is just using the human judgement (and human speed of operation) in PDAF, same principle 

I focus manually through the optical viewfinder by contrast.



Doesn't have to be a stationary subject either.

[BJL]

... then through optical viewfinder is just using the human judgement (and human speed of operation) in PDAF, same principle ... so probably both manual focusing techniques shall be included

I think Doug Herr (telyt) is right, that the focus detection we use in manual focus is basically detecting contrast, not detecting phase differences. (Unless you still have a split-image rangefinder style VF in your SLR.)

Some differences in MF between using the reflex mechanism and focusing screen of an SLR vs using the live preview of an eye-level EVF or rear screen:

- the reflex system suffers from possible misalignment of the mirrors and focusing screen relative to the sensor (as seen in the inaccuracy of SLR PDAF in the tests, improved by calibrating for the lens-body combination)

- the image in the OVF is of lower resolution and smaller than is possible with an enlarged live preview

- the image in the OVF is somewhat more detailed than with an unenlarged live preview, and also far larger than an unenlarged rear screen preview.

Using enlarged preview might not be possible with some moving subjects, adding one more reason why moving subjects are the last bastion of advantage for optical reflex viewfinders.

[deejjjaaaa]

Unless you still have a split-image rangefinder style VF in your SLR.

I always replace stock screens w/ split prism screens cut from Nikon K3 OEM screen...