I do realize the shock value of you saying 3MP to make a point. But MP does matter... it just has diminishing returns as you increase it. As a counter to your 3MP example, I'll give GigaPixel images as the opposite end of the spectrum (although as technically awesome as it would be... it's not remotely feasible in a handheld camera 'currently').
Going from 1 > 3 > 12 > 20 > 30 > 45 is not as lineal as the numbers suggest, as you have to take into account the % increase... but this really isn't new info.
Couple key generic points when looking at MP/DPI/Resolution...
- Is the optical system actually able to take advantage of the increased MP?
- Sure, I can scan on my cheap flatbed scanner @ 4800dpi or 600dpi, but does the 4800 really look any better than the 600 (hint... it doesn't).
- However for the RF system w/ L Glass, we know the ceiling on what MP can be resolved is very high... so lets assume this isn't as much of an issue here and we still have a lot of headroom.
- Are the workflows used able to process/store the increased MP?
- This is where the computer you are using comes into play. Drive Size/Speed, RAM, CPU, GPU (for accelerated workflows) etc.
- This is also sometimes subjective when there is hardware that can process the MP fast, but there is a reluctance of upgrading to that hardware (due to cost, feasibility, or whatever).
- Does increasing it 'now' matter?
- Basically, is the normally produced product going to need the MP to justify the overhead/cost of having more MP? This is where things turn subjective and there is no pleasing everyone.
- Are the sacrifices worth it?
- This is where cost, speed, and ease of use come into play, and is also semi subjective.
The thing is Canon combines a lot of feature they think makes sense for the camera that they think they can sell for the people looking for those feature. There is no pleasing everyone here... and most will stand behind what they want/need as fact (when it's just fact for them). Also, given that Canon makes multiple models, there is always the segmentation of choice from the consumers (based on what available)... that eventually they will deliver models that hit on the 'most important' feature someone needs.
I believe we are beyond anything new coming out at less than 20MP. I also think that for a camera of this caliber that 'at least' 30MP was expected for the R3 (honestly I was hoping for more).
My threshold of where the 'line in the sand' is, is just that... a line in "SAND". Say I want the best possible image that I can crop the heck out of... I may deem min 45MP. Say I want to limit rolling shutter or get more FPS... I know I will need to sacrifice MP to get a faster readout due to "today's technology"... so the 30MP is actually not looking that bad.
Personally I love technology pushing the limits... even if it's not something I will use now, it usually refines processes that I will use later. I also do not give the excuse that 'if I get it my current computer will melt'... since my computer specs are usually great (or I'll upgrade if needed).
Here is a good example we hear on CR. (I hope PBD doesn't mind but I'm going to use him as an example because he has been very vocal about it lately.) Anyways, he has a workflow where he uses 20MP for paid jobs where the end product is huge, but gives the desired results, without the hassle of dealing with larger files. If Canon wants to sell him the camera, they have to cater to what he wants. From what I gathered he doesn't really want more MP
, but he does like the speed and other items the R3 has to offer. Canon might have catered to him when building up the R3. Actually, I don't think he is alone... as 1DX users that prefer other stats over MP might be eying up the R3 too.
Here is where I disagree with him (now please note this is subjective for both of us). If I could have my cake and eat it too, I would! I would love to see the R3 at 45+ MP if it didn't sacrifice the other specs. The additional overhead of dealing with higher MP images does not put me off. However I am also a realist, and I don't think Canon can deliver that camera at this time... something would have to give.
At the end of the day... Canon is releasing a R3. This may or may not be the camera you are dreaming of. If not, wait until a Canon camera is released you do want is made or buy another brand.