6D Sensor... why?

[K-amps]

20MP vs 21MP vs 22MP pixel pitch will have ZERO noticeable difference on SNR....
I'm picky and pixel peepy as heck and there is no way I'd be able to tell if the same exact tech was used on a 20MP a 21MP and a 22MP sensor, not remotely.

(And did the D800 not prove a thing? 36MP and very, very good high ISO.)

You are even more hardcore than I am...

 

[K-amps]

high MP fullframe sensors... high compared to what?

Compared to the 30+ MP senors from Sony.

so they decided to put money in R&D to produce yet another FF sensor instead of using the 5D MK2 sensor?
if it is a new developed sensor and not some camouflaged 5D MK2 sensor.

You missed the last part of my post where I suggested is might be the same sensor die as the 5D MkIII, but with a greater number of pixels failing to make the grade. These would then be averaged together as a single pixel. If you do that across a sensor you get very respectable performance but with a lower total MP count.

That wouldn't work out, you'd just have a ton more hot pixels and I've never heard of a manufacturer calling poorly made 22MP sensors that have 2 million dead pixels a 20MP sensor. And just think, they list the image dimensions, how do you get that change with random dead pixels here and there throughout?

It does seem weird, since you'd think just re-using 5D3 sensor would be more efficient. But I can't imagine they would do something that would cost them money so you'd think it would somehow have to be some sort of masking off or less masking off of another sensor or maybe they found a way to somehow pump these ones out more cheaply because something about them makes them noticeably less expensive to make than say the 5D3 or 1DX sensor.

Or maybe they did have a low ISO DR breakthrough but what on earth were they thinking to be so slow to get they needed that and not get that tech in the 5D3 and 1DX? Those user bases will raise a storm, if just a few months later a low end FF has a sensor that blows the ones they have away. It would at least give one a lot of faith about the 5D4 though. Something would seem to have been supremely poorly thought out and planned in Canon management.

He was probably thinking CPU's and yields.... Sensors / Monitors don't work that way

 

[UrbanVoyeur]

You missed the last part of my post where I suggested is might be the same sensor die as the 5D MkIII, but with a greater number of pixels failing to make the grade. These would then be averaged together as a single pixel. If you do that across a sensor you get very respectable performance but with a lower total MP count.

That wouldn't work out, you'd just have a ton more hot pixels and I've never heard of a manufacturer calling poorly made 22MP sensors that have 2 million dead pixels a 20MP sensor. And just think, they list the image dimensions, how do you get that change with random dead pixels here and there throughout?

In sensor production, it is not all or nothing when it comes to pixels. Yes, there are dead pixels and hot pixels, but that's not what I'm talking about. More common problems are noisy pixels, non-linear pixels and low ISO pixels. Very often these can be corrected using the average value of a group of adjacent pixels, rather than rely on just that one. Or by comparing them to nearby pixels and using an offset. Sometimes the only solution is to ignore the output. Typically, these problem pixels are not uniformly distributed - they tend to cluster, while the rest of the pixels may be perfect.

Since you can't use a sensor that is high res everywhere except the lower right corner where the problem pixels are, any solution must be applied uniformly to the whole sensors. Even if it means ignoring or averaging the output of perfectly good pixels.

Each sensor produced is tested and the response of each pixel measured. If a model of averaging, offsetting or ignoring problem pixels is found that will produce a lower resolution but perfectly performing sensor, the model is a applied and the sensor is used at the lower MP count. This is how many small, compact camera sensors are produced. I also think it is where the SLR AF sensor come from.

It is not necessary to apply the same correction model to every problem pixel on a given sensor as long as you end up with a uniform distribution of good pixel clusters. On a single sensor, there may be a mix of non-linear pixels, noisy pixels and pixels that only respond at high or low light levels. As long as the corrections gives results in a consistent and uniform pitch, say groups of 2, 3 or 4 pixels, it can be tailored to correct each problem separately. Various correction models can be tested mathematically to find the optimal solution - cleanest output, highest MP count. The results are stored in sensor correction array map that is ROM on the chip.

This method has limitations. Too many problem pixels in one area or across the sensor, and all correction models fail - the sensor is discarded. But is is quite possible to start with a sensor that won't pass at 24 MP but with correction, will work at 12 MP. Or start with 40 MP and get 20 MP. Not all the corrections are simple averaging, so the relationship between the starting point and ending point is not always a factor of 2 or 3.

 

[Marsu42]

can someone explain why the 6D has a new developed 20.2 MP sensor?

The reason imho is very, very simple: To put the specs below the 5d3 (22mp) and 5d2 (21mp). The design of the 6d is purely marketing driven (af, x-sync) - if they couldn't get away with simply recycling the 5d2 sensor and didn't want to cannibalize the 5d3 a "new development" was the only option.

I still expect to 6d to have very low banding/ read noise, but this is not only due to sensor design w/ Canon tech but has to do with the rest of the camera electronics. As for dr/iso, I'm curios to see the reviews, but I don't think it'll save the 6d from forgetfulness.