Archive 2017 · Sony a9 28mp total, 24mp effective

Mystik
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p.1 #1 · p.1 #1 · Sony a9 28mp total, 24mp effective

According to Sony's specs, the a9 actually has a 28mp sensor, though only 24mp is used for image sensing. What is the other 4mp being used for? My hunch is that based on the PDAF performance of the camera, particularly with adapted lenses, that these pixel are dedicated to PDAF....sort of like Canon's dual pixel, but not covering the entire image sensor? Sony had patents for this that showed up on SAR a while back. Purely a hunch...I have no technical basis to support this, so I was wondering if anyone else had any insight on this.

A9 Specs:

https://www.sony.com/electronics/interchangeable-lens-cameras/ilce-9/specifications

a7rII Specs

https://www.sony.com/electronics/interchangeable-lens-cameras/ilce-7rm2/specifications

Jun 27, 2017 at 06:16 AM

mogul
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p.1 #2 · p.1 #2 · Sony a9 28mp total, 24mp effective

Mystik wrote:
According to Sony's specs, the a9 actually has a 28mp sensor, though only 24mp is used for image sensing. What is the other 4mp being used for? My hunch is that based on the PDAF performance of the camera, particularly with adapted lenses, that these pixel are dedicated to PDAF....sort of like Canon's dual pixel, but not covering the entire image sensor? Sony had patents for this that showed up on SAR a while back. Purely a hunch...I have no technical basis to support this, so I was wondering if anyone else had any insight on this.

A9 Specs:

https://www.sony.com/electronics/interchangeable-lens-cameras/ilce-9/specifications

a7rII Specs

https://www.sony.com/electronics/interchangeable-lens-cameras/ilce-7rm2/specifications

If it isn't in the imaging circle, it can't be used. Most sensors are bigger than the image...the off site can be used for digital stabilization though

Jun 27, 2017 at 10:27 AM

Mystik
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p.1 #3 · p.1 #3 · Sony a9 28mp total, 24mp effective

mogul wrote:
If it isn't in the imaging circle, it can't be used. Most sensors are bigger than the image...the off site can be used for digital stabilization though

Yes but you're typically looking at less than 1mp not being used. I.e. the a7RII.

Jun 27, 2017 at 10:34 AM

joelRichards
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p.1 #4 · p.1 #4 · Sony a9 28mp total, 24mp effective

that's been my guess too but I haven't found any "official" confirmation. Other tests (red channel banding) suggest that the A9 is still using shaded pixels like previous Sony E-mount cameras. So I'm a little less sure now...

Jun 27, 2017 at 11:38 AM

snapsy
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p.1 #5 · p.1 #5 · Sony a9 28mp total, 24mp effective

Bill Claff, Jim Kasson, and I worked on identifying the PDAF sensors on the A9. There are approximately 350 rows of PDAF sensors, all on the blue channel. We haven't worked out how many sensors are on each row. You can read more details here:

https://www.dpreview.com/forums/post/59676460

Jun 27, 2017 at 12:29 PM

starlights
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p.1 #6 · p.1 #6 · Sony a9 28mp total, 24mp effective

Wouldn't extra pixels be needed for the IBIS? sensor movement?
ps - I am not a Sony person, just chiming in

Jun 27, 2017 at 01:45 PM

Mystik
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p.1 #7 · p.1 #7 · Sony a9 28mp total, 24mp effective

snapsy wrote:
Bill Claff, Jim Kasson, and I worked on identifying the PDAF sensors on the A9. There are approximately 350 rows of PDAF sensors, all on the blue channel. We haven't worked out how many sensors are on each row. You can read more details here:

https://www.dpreview.com/forums/post/59676460

So read the whole exchange...it sounds like the PDAF pixels are paired sensels on the blue channel that arent gathering image data .... and that the imaging data for these pixels are interpolated using data from the surrounding pixels?

Sorry if I'm not following...definitely way over my head here lol

Jun 27, 2017 at 02:03 PM

snapsy
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p.1 #8 · p.1 #8 · Sony a9 28mp total, 24mp effective

Mystik wrote:
So read the whole exchange...it sounds like the PDAF pixels are paired sensels on the blue channel that arent gathering image data .... and that the imaging data for these pixels are interpolated using data from the surrounding pixels?

Sorry if I'm not following...definitely way over my head here lol

That's the belief. You're doing just fine

Jun 27, 2017 at 02:16 PM


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