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 p.69 #2 · Official: Canon Announces the EOS 6D Mark II | |
Ubtree wrote:
I wonder whether some of the issues regarding Canon sensors (highlighted by the disappointing 6D MkIIs DR) might be due to manufacturing reject levels for sensors. I am not an expert in sensor manufacture, and no doubt those with more knowledge will be able to correct and add to the following.
Sensor costs ignoring failure rates
It is reasonable to assume that, ignoring failure rates, the cost of producing a sensor is broadly directly proportional to its area. If so, you would expect the cost of a FF sensor to be 2.59x that of an APS-C sensor.
Failure rates
When they are manufactured, a proportion of sensors will inevitably be rejected by QC. If, for example, a 10mm x 10mm sensor has a 10% failure rate, the probability that it will pass the QC check is 90%. Each half of a 10mm x 20mm sensor produced in the same way would have an 90% probability of passing, and the chances of both sides passing would be 90% x 90% ie. 81%. Therefore the failure rate would be 19%.
On this basis, the general formula for the failure rate is:
F = 1-(1-f)^(A/a)
where f is the failure rate of a sensor of area a, and F is the failure rate of a sensor of area A.
Implications
I am going to assume that an APS-C sensor would cost $100 to produce, if there were no QC rejects (ie. 100% success rate). (I dont know how accurate this guess is, but it should be good enough to illustrate my point.)
An FF sensor is 2.59x the size of an APS-C sensor, and therefore would cost $259 to produce, if there were no QC rejects.
We can only guess at the manufacturing failure rates they will depend on the manufacturing process and how well it is controlled. But the following gives cost of APS-C and FF sensors after allowing QC rejects, and the FF failure rates, based on the above assumptions, for different
APS-C failure rate
APS-C sensor cost
....
....FF sensor cost
....FF failure rate
..........5%........................$105
..
...$296
.12%
........10%........................$111
.$340
.24%
........15%........................$118
.$395
.34%
........20%........................$125
.$462
.44%
........25%........................$133
.$546
.53%
........30%........................$143
.$652
.60%
........35%........................$154
.$790
.67%
FF sensors are much more difficult / expensive to make. And if the failure rates are not well controlled, there are serious consequences.
Suppose Manufacturer S had put in the effort and money to get to grips with their manufacturing process, such that their failure rate (for APS-C sized sensors) was only 10%, whereas Manufacturer C had not done so, and their corresponding failure rate was 30%:
It would make little difference to the APS-C sensor: compared with Manufacturer Ss cost of $111, Manufacturer C would have a price penalty of only $32.
The effect on the FF sensor would be huge: compared with Manufacturer Ss cost of $340, Manufacturer Cs would have a price penalty of $312.
Conclusion
If Canon did not got its manufacturing failure rates under control for its latest technology sensors, it could still use the new technology for its APS-C cameras (since the cost penalty is small), and could still use the new technology for its premium FF cameras (eg. 5D MkIV), since there would be enough margin in the product to absorb the cost penalty. But it wouldnt be able to afford to use the latest technology for a budget FF camera (such as the 6D MkII). Does this explain the mystery of the 6D MkII sensor?
12 years ago, Canon was at the forefront of FF sensor technology. But perhaps it hasnt been willing / able to make the investments needed to compete with manufacturers whose production isnt confined to inhouse needs.
...Show more →
I think it's much simpler than this - Canon has multiple sensor fabs, which varying levels of process widths and technology. They likely relegated the 6DM2 to the older fab.
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I am really wishing now that I had never got a 6D until now (6D Mk II), but I borrowed a 5D Mk III from CPS and I wanted a full frame camera. A 6D came up locally for a great deal, and I've been really happy with it, but I would be really excited to get the 6D Mk II moving up from the 80D, without having the 6D in the meantime.