Patent: Quad pixel AF sensor

Sporgon

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I'm curious as to why Canon would use all vertical sensing DPAF on sensor when in their higher end DSLRs the AF points that aren't cross type ( or dual cross type) are horizontal sensing.

Just thinking on this, I thought DPAF had the split vertical, left and right, (with camera horizontal) so it would be horizontal sensing, not vertical ?
 
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Sibir Lupus

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Given they discussed QPAF in the orginal DPAF patent way back in arund 2012 it's a long time coming. They also discussed asymmetric DPAF and suing it for HDR. One does not really need QPAF for x-type, they could easily make groups of pixels with DPAF in the perpendicular direction so AF points could consist of just two orientations of DPAF. Would be easier to implement and have greater sensitivity than QPAF.
My guess for the delay might have to do with processing power catching up with QPAF tech, as I'm sure it needs at least twice as much calculations vs DPAF II. We'll either see a cranked up DIGIC X in the R1, or possibly dual DIGIC X to handle QPAF.
 

jam05

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I'm curious as to why Canon would use all vertical sensing DPAF on sensor when in their higher end DSLRs the AF points that aren't cross type ( or dual cross type) are horizontal sensing.

Just thinking on this, I thought DPAF had the split vertical, left and right, (with camera horizontal) so it would be horizontal sensing, not vertical ?
Even the ctoss types are arranged in columns and have vertical sensing and horizontal components. Now rotate the camera. That pixel is still in it's original alignment.
 
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Mt Spokane Photography

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Making a quad pixel sensor isn't so difficult but the software to operate it must be a nightmare. If it ever comes to market, the s0ftware is going to be fairly simple at first. I expect that they have been working on software for years in research, but in the real world I'd bet that there are all kinds of strange issues. I've seen Canon patents in the past for "n" numbers of subpixels since they were dealing with the electronics portion and patents want to cover every possible permutation.

When dual pixel came out, Canon said that it was the software that was the problem with bring it to market and they brought in experts from their professional video division to help figure it out. Even then, it was difficult. Presumably, there are now engineers with a much greater understanding as to how a quad pixel software might work to have autofocus vertically and horizontally from the same pixel. I think that diagonally will be a future development if ever. The other possibilities like independent gain for each sub pixel may be future developments, the complications in processing something like that will also require a lot of testing. They have it working for dual pixel sensors, the processing power needed may restrict it to video cameras right now, but its coming.
 
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adrian_bacon

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Quad gain output would not surprise me in the RF mount C700 replacement.
I would not expect it in a flagship hybrid mirrorless but I could see it in a flagship cinema camera.
Well, Canon is always getting bagged on for not enough dynamic range... If they went with quad gain in a flagship like the R1 and got a very usable 15-16+ stops, that would put a lot of heat down on Sony and Nikon.
 

yeahright

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I'm curious as to why Canon would use all vertical sensing DPAF on sensor when in their higher end DSLRs the AF points that aren't cross type ( or dual cross type) are horizontal sensing.

Just thinking on this, I thought DPAF had the split vertical, left and right, (with camera horizontal) so it would be horizontal sensing, not vertical ?
If, as in Canon's current DPAF cameras, the pixels are split horizontally (meaning the line that splits the pixel in two halves is vertical and the pixels are therefore horizontally next to each other, i.e. left and right pixel half in horizontal, i.e. landscape camera orientation) in DPAF, then the arrangement can focus on vertical structures. Horizontal structures appear identical in both left and right pixels and thus cannot be used for focusing. Because focusing relies on the different appearance of the structure to focus on in the two pixel halves.
 

Sporgon

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If, as in Canon's current DPAF cameras, the pixels are split horizontally (meaning the line that splits the pixel in two halves is vertical and the pixels are therefore horizontally next to each other, i.e. left and right pixel half in horizontal, i.e. landscape camera orientation) in DPAF, then the arrangement can focus on vertical structures. Horizontal structures appear identical in both left and right pixels and thus cannot be used for focusing. Because focusing relies on the different appearance of the structure to focus on in the two pixel halves.
Ah, thanks for that. I’d just assumed that they worked like a split image focus finder but I now see it’s more like a rangefinder. (y)
So in fact it’s the same orientation as the non x type on DSLRs.
 

AlanF

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Ah, thanks for that. I’d just assumed that they worked like a split image focus finder but I now see it’s more like a rangefinder. (y)
So in fact it’s the same orientation as the non x type on DSLRs.
Just make sure your subject is not a vertical line 1 pixel wide on the sensor.
 
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usern4cr

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Since we're on the subject of quad-pixel or dual-pixel focus, I was wondering if anyone knew of the details of how a phase detect (not contrast detect) pixel actually works. Everywhere I look on the internet they don't really explain it. I do understand that there are 2 sensor areas next to each other and there is some sort of micro lens in front of each area that "somehow" splits the light differently into the two areas. But how can they make one of the areas focus at a nearer distance relative to the farther distance of the other sensor so that they can decide which direction to move the focal distance to reach the correct focus? Do they have a concave lens above one and a convex lens above the other? And if so, why would this technique be sensitive to vertical lines and not to horizontal lines (which would be what I'd expect for a contrast detection sensor but I'm interested in a phase-detect sensor).

This is the kind of detail I'm interested in, if anyone knows?
 

AlanF

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Since we're on the subject of quad-pixel or dual-pixel focus, I was wondering if anyone knew of the details of how a phase detect (not contrast detect) pixel actually works. Everywhere I look on the internet they don't really explain it. I do understand that there are 2 sensor areas next to each other and there is some sort of micro lens in front of each area that "somehow" splits the light differently into the two areas. But how can they make one of the areas focus at a nearer distance relative to the farther distance of the other sensor so that they can decide which direction to move the focal distance to reach the correct focus? Do they have a concave lens above one and a convex lens above the other? And if so, why would this technique be sensitive to vertical lines and not to horizontal lines (which would be what I'd expect for a contrast detection sensor but I'm interested in a phase-detect sensor).

This is the kind of detail I'm interested in, if anyone knows?
This is the best explanation - Marc Levoy's applet http://graphics.stanford.edu/courses/cs178/applets/autofocusPD.html just rejig it so the focussing sensors are on the image sensor for mirrorless.
 

usern4cr

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This is the best explanation - Marc Levoy's applet http://graphics.stanford.edu/courses/cs178/applets/autofocusPD.html just rejig it so the focussing sensors are on the image sensor for mirrorless.
Thanks, AlanF, for the link. While the example shows how to focus on a bright dot on a black background with 2 lenses and 2 arrays of sensors that are not on the final image sensor itself, I really would like to see a diagram where they show how they put the system together on the final image sensor itself. It's difficult to imagine each pixel of the 45MP array having such a system in each pixel.
 

Joules

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Dual Pixel AF = DSLR Lines AF
Quad Pixel AF = DSLR Crosses AF
Octa Pixel AF = DSLR Double-Crosses AF
Wouldn't Quad Pixel AF already be a bit more precise than just a cross, as you'd get two pairs of horizontal contrasts, and two of vertical (although each along the same line, so different from double cross) in each pixel with QPAF?
 

AlanF

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What's been really impressive is the way that Canon has been able to get the current DPAF to focus so fast and accurately. Some of us were worried that the processing of the dual pixels would be more processor intensive not be able to compete with embedded phase detect, but the R5 is up there with Sony speed and with a more flexible system, not requiring missing out pixels to accommodate phase detect.
 

Mt Spokane Photography

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What's been really impressive is the way that Canon has been able to get the current DPAF to focus so fast and accurately. Some of us were worried that the processing of the dual pixels would be more processor intensive not be able to compete with embedded phase detect, but the R5 is up there with Sony speed and with a more flexible system, not requiring missing out pixels to accommodate phase detect.
A bigger AF area has been a development as well. I recall patents with various tweaks to sensor design proposed that would allow more accurate AF at the edges and corners. I wonder if any of those have been implemented. A global shutter type sensor has been rumored, and perhaps quad pixel as well for a R1.

As I understand it, a global shutter CMOS sensor will have memory associated with each photosite and values will be saved in those memory sites all at once. Then read out to the camera processor and memory in the standard parallel/sequential fashion. It may require backlit sensor technology to do that. Canon has a ton of patents for doing it, its just a matter of cost to get enough good sensors out of the process. Canon is extremely price conscious, they squeeze every penny.
 
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