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12-28-2014, 06:02 PM   #1
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Possibility of on-sensor phase detection autofocus?

With Ricoh's recent patent of using a translucent mirror I was wondering if this technology would lead Ricoh to use on-sensor phase detection autofocus. I can't imagine the translucent mirror splitting the light three ways and still maintain decent low light performance.

12-28-2014, 07:19 PM   #2
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That would be cool. The need to sometimes calibrate lenses for optimum performance is a serious fly in the ointment of DSLR's.
12-29-2014, 07:00 AM   #3
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are you asking because live view uses contrast AF whereas using the viewfinder uses phase detection AF (through the mirrorbox?) ? some other manufacturers have phase detection without a mirrorbox... usually on mirrorless cameras, but i think some dslrs can use both contrast and phase simultaneously
12-29-2014, 08:06 AM   #4
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QuoteOriginally posted by ppppsssstttt Quote
are you asking because live view uses contrast AF whereas using the viewfinder uses phase detection AF (through the mirrorbox?) ? some other manufacturers have phase detection without a mirrorbox... usually on mirrorless cameras, but i think some dslrs can use both contrast and phase simultaneously
I'm unaware of a DSLR that can use PDAF and CDAF simultaneously. Maybe the Ricoh patent will lead to a camera that can use on-sensor PDAF and maintain an OVF.

12-29-2014, 08:37 AM   #5
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i was thinking of canon's dual pixel cmos AF. i guess technically it does phase, then contrast, but the sensors for phase are not on a separate chip per se.

Canon Dual Pixel CMOS AF: Autofocus secrets of the Canon 70D explained

QuoteOriginally posted by IchabodCrane Quote
I'm unaware of a DSLR that can use PDAF and CDAF simultaneously. Maybe the Ricoh patent will lead to a camera that can use on-sensor PDAF and maintain an OVF.
12-29-2014, 09:11 AM - 1 Like   #6
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QuoteOriginally posted by ppppsssstttt Quote
i was thinking of canon's dual pixel cmos AF. i guess technically it does phase, then contrast, but the sensors for phase are not on a separate chip per se.

Canon Dual Pixel CMOS AF: Autofocus secrets of the Canon 70D explained
Canon's dual-pixel technology only works in Live View mode. When shooting through the VF, it functions strictly with PDAF like any other DSLR. Maybe Ricoh has a solution that gets around this.
02-16-2015, 02:02 PM   #7
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I really know nothing about autofocus technology. I would be happy if Pentax designed a camera where phase detection would work with continuous mode AF-C and contrast detection would work with single mode AF-S. I really don't need any hybrid between the two.
02-16-2015, 02:38 PM   #8
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QuoteOriginally posted by IchabodCrane Quote
I'm unaware of a DSLR that can use PDAF and CDAF simultaneously.
Not with an optical viewfinder, though I guess that is sort of a given


Steve

02-16-2015, 03:04 PM   #9
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You can use PDAF and CDAF simultaneously, but only with in live view. The advantage is that PDAF is fast, and tells the lens where to go. The fine tuning can then be done by CDAF to get absolute spot on accuracy...


As for getting the PDAF sensors on the sensor to work while using the OVF... I doubt that is possible. The sensors on the separate chip that sits in the mirror or so are much more light sensitive than the ones you can fit onto the imaging sensor itself (space...), that's how they can work so well even though only a small part of the light hits the PDAF sensor. You would have to let through most of the light to the imaging sensor so that those PDAF sensors work well enough... which means you won't see a thing through the OVF.


However the (switchable) translucent mirror excites me because it would enable Pentax to have a really bright OVF as long as you are not using the AF system. If you do, the camera reduces the light that goes to the OVF, and the camera is able to focus even in low light. Even lower than before if you let more light than usual to the PDAF sensor.


Having PDAF on image sensor sensors would still be neat for live view, videos etc..
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