avsquare
Senior Member
There are some good points made. I guess unless we work with the design team at Canon, we will never know the true answer. Here are some thoughts I have:
i) The 5D3 sensor stands on its own... meaning that it produces great photos for those who know how to get the most out of their camera. Canon was careful not to produce a sensor that was materially and effectively inferior than its predecessors... namely the 5d Classic and the 5D2. The 5D3 sensor is every bit as good if not marginally better than its ancestors.
ii) The 1DX sensor maxes out at 18mp. I think that most of us would agree that if Canon introduced an 18mp sensor, the entire Canon community would be in an uproar. It would be intolerable to go backwards from a 21mp sensor in the 5D2 to an 18mp sensor in the 5D3. It was bad enough that the competition came out with a 36mp sensor.
iii) Many rumours are predicting that the upcoming entry level full frame will incorporate the same 5D3 sensor as part of its package. This may become the first time that a 5D sensor has been shared with another model.
I think the main reason why different sensors are used is to ensure that their product lines are clear.
The new sensors introduced in 5D3 and 1DX both features gapless microlenses which is not seen in previous FF bodies, which explains the huge improvement in ISO performance VS 5D2 and 1Ds3. The 1DX's pixel size is slightly larger than the 5D3's and 1DX boasts a 16 channel read out compared to 5D3's 8 channel - that would explain why 1DX's ISO performance is better and able to achieve 12FPS compared to 5D3's 6FPS.
One thing about Canon, as everyone would have agreed, is their strength in marketing. These people (in a negative way), don't make improvements look good on paper only, but also the product itself. Just like when you compare the 5D3 with 5D2 on paper, yes you do see improvement paperwise, you may not think much but when you've used it, you'd see the difference.
Same goes to 1DX and 5D3. Although the 1DX is a few MP behind 5D3, somehow based on my limited use, I think there's a slight difference in the IQ between the two.