There are rumours that Canon are in the process of building a 75-megapixel DSLR
Much as I hate to stoke the fires of those rumours, it's worth reviewing exactly what's being proposed here and what it might mean, if only to provide a measure of rumour control. So, in the spirit of not getting excessively carried away with the numbers game, what do we know?
What do we know?
Well, not very much at all, on the face of it. This is, as far as I can tell, not an official Canon announcement, although I'm sure they've no objection to the publicity. It's also not the first time there've been rumblings of sensors in the multiple tens of megapixels range; there was talk back in 2010 of an APS-H sensor with over 120 million photosites on it, although that wasn't connected with a particular product. Even the cellphone people are now talking about a 41-megapixel camera with Nokia's Lumia 1020.
So, the number may be big, but it isn't actually all that big compared to preexisting things. And even if it was, as we recently saw with Magic Lantern's innovative dynamic range tweak for the 5D Mk. 3, people are sometimes willing to overlook some quite severe ancillary problems in order to gain things like dynamic range. More than that, a 75-megapixel sensor equates (were it a 16:9 frame, which it probably won't be) to an image of around 11.5k by 6.5k, modulated by whatever derating factor you feel is appropriate for Bayer imagers.
Only that's the first interesting thing about it: it isn't a Bayer sensor, so really none of that applies. Sources are a bit hazy on exactly what it is, although there are suggestions that it's related to a patent Canon put out back in May which involved a Foveon-style multi-layered chip, with co-sited RGB pixels. That, frankly, is a lot more interesting than a high pixel count, especially as a bit of basic mathematics assuming 25 megapixels per RGB channel would indicate that it's still well over a 6k by 3.5k camera – in true RGB, limited only by the necessary low-pass filtering to prevent aliasing. This is more complete RGB resolution than any electronic camera of which I'm aware.