Higher MP is bad?

apersson850 wrote in post #10891587
I'd say that's about as true as a blanket statement as anything can be.

Apparently some of you don't do much nature photography.

If I'm shooting a hummingbird from 40 feet away with a 400 mm lens, having a higher-resolution sensor (more pixels) is huge. And if I have relatively low per-pixel noise, then all the better. Because I'm going to need to crop the hell out of that image during PP.

It's always the focal length-limited situation that makes these arguments, oops , discussions, go in different directions! If Canon doesn't make a lens long enough for my needs/budget(and I can't get closer to my subject for physical reasons) then smaller pixels (more MP) has the potential to get me the shot where the big pixels (lower MP) won't. In this situation, I'm not saying to myself, I'll make my standard 8x12 print from this one, so I don't need any more MP

Afield wrote in post #10891574
Who in the heck does that?

Cropping an image to 100% and cropping the same image with half the resolution to 200% is the same thing as upsizing the lower-res image. That's what you're doing when you crop a lower MP camera to the same degree as with a higher MP camera. So there is still no noise difference.

And how is not accurate as a blanket statement? Everything in photography comes back to sensor size and enlargement factor.

qbfx wrote in post #10891458
I think the point being made is that higher MP sensors need better glass in order to take advantage of their increased resolution, not that they need better glass to achieve the same perceived resolution in the same "view" size as with a lower MP sensor. Hope this makes sense

Sure, but higher pixel count will still help until the lens is outresolved...and at this point, claiming that x lens is outresolved by y camera is purely conjecture. As an example, the 55-250 at 250mm wide-open (its weakest setting) resolves 1756 lw/ph in the center on a 350D, according to Photozone...and it resolves 2150 lw/ph at a 50D. So obviously it hasn't been outresolved, otherwise the resolution wouldn't have increased.

I think sharpness lost through camera shake is a much bigger and more common issue than a not-good-enough lens, so worrying about having the best lenses doesn't really matter unless that is addressed.

toxic wrote in post #10892001
Cropping an image to 100% and cropping the same image with half the resolution to 200% is the same thing as upsizing the lower-res image. That's what you're doing when you crop a lower MP camera to the same degree as with a higher MP camera. So there is still no noise difference.

Yes, but there's still a tremendous difference in resolution, and this will become obvious when you try to make medium-to-large prints of each of these images. Who cares if there's technically no more noise in a 200% crop taken from a lower-res sensor when the results look like pixelated garbage?

You're also assuming equal-quality sensors here. Better sensors yield less per-pixel noise. Look at 100% crops of shots with a 50D and a 7D and you'll likely see less noise with the latter.

You seem to be assuming that everybody uses 80% or more of the pixels available in each shot, where the image quality difference between a 10 MP sensor and an 18 MP sensor is negligible at anything less than a poster-sized print. But the reality is that not everybody shoots landscape or studio. When I shoot birds, I routinely crop away 40-80% of my image. So resolution is incredibly important, as is having very clean pixels.

This is really an interesting topic , actually im looking the best walkaround lens to maximize use of the 18mp resolution ... so far im still confuse , should we buy for "L" or EF-S ?

If you have to ask, don't buy L.

As has been said, we have yet to see sensors outresolve lenses. You will see this happen when, using the best techniques and the lens "sweet spot" an image viewed at 100% will show "pixel smear". Now, you can get over that with either "pixel binning" or just keeping the image downsized, but I personally would prefer to keep back from that point of wasting/discarding pixels.

And, as has been said, up to this point there is no "loss" with the greater resolution. A high megapixel image will always look at least as good as a lower res image taken with identical settings and on the same size sensor, viewed at the same size. So, in this sense, those conditions can even overcome the "outresolved lens" business, despite the fact that I'd personally prefer to avoid that!

Now sensor noise is something different. We can't compare between two sensors of different resolution but the same size, because, with the current technology we don't have two like that to compare. We can compare the 7D with the 40D, 50D, and/or 60D, but from everything I've heard, high ISO noise performance has improved over the generations so that the higher resolution sensors may or may not have an overall similar amount of noise but the technological gains have increased the pixel-level capacities to gather light and also when you view the 7D 18MP file downsized to view alongside a 40D 10 MP image you will have the 7D noise compressed and minimized (although along with relevant detail -- a tradeoff).

Now, all this does not take into account differences between, say, the 5D2 full frame sensor and the 7D when it comes to image quality issues. Now is not the time to start a full frame vs crop debate! And, let's not even think about the upcoming 1Ds4!

"If you have to ask, don't buy L".

Actually, it sounds like he should buy one, to see the difference good quality optics can make. And EF-S is limited to crop frame, so no chance of keeping them when we all eventually are using full frame and crop frame is consigned to the history books.