Once again, this rhetoric keeps cropping up and it is completely incorrect! NEVER, in ANY CASE, is more megapixels bad because of diffraction! That is so frequently quoted, and it is so frequently wrong.
I'm not saying its worse, its just the extra MP don't make any difference to the resolving power once diffraction has set in. Take another example - scan a photo which was a bit blurry - if a 600dpi scan looks blurry on screen at 100%, you wouldn't then think 'let's find out if anyone makes a 10,000dpi scanner so I can make this look sharper?' You'd know it would offer no advantages - at that point you're resolving more detail than is available - weakest link in the chain and all that...
The aperture used was f/9, so diffraction has definitely "set in" and is visible given the 7D's f/6.9 DLA. The subject, in this case a Juvenile Baird's Sandpiper, comprised only the center 25% of the frame, and the 300 f/2.8 II w/ 2x TC STILL did a superb job resolving a LOT of detail:
You've got some great shots there, very impressive
- and it clearly does show the difference between good glass and great glass. But the f9 300 II + 2x shot isn't 100% pixel sharp like your native 500/4 shot is. I'm not saying there's anything wrong with the shot - it's great, and the detail there is still great. Its just not 18MP of perfection great. A 15MP sensor wouldn't have resolved any less detail behind that lens, but that wouldn't have made a 15MP shot any better.
This thread is clearly going off on a tangent here, as pixel peeping is rarely anything to do with what makes a great photo - its just we are debating whether the extra MP are worth it. And just to re-iterate, great shots jrista
The reality is that detail with X contrast at f/6.9 has some value <X contrast at f/8, and can be restored to X contrast with sharpening. I can make f/6.9, f/8, and f/11 24" prints all day long and you won't be able to tell me which is which.
While sharpening has the potential to be OK in moderation, just don't take it too far. Its all down to personal taste of course, but I can't stand the output of compact cameras which are way beyond their diffraction limits and have the sharpness cranked all the way up to 11 to try to retain something, but instead they just create ugly halos around edges. Sharpening isn't perfect for recovering detail which isn't there. Something like this
offers a glimpse of what might be possible in the future.
However, back to the meaning of my original point, do we really need all these MP? Do you need
24MP from your crop camera? Its not like the early days of digital photography when there were real advantages of increasing the MP - going from the Canon D30 to the Canon D60 represented a very real improvement in quality - going from 3 to 6MP is a very real difference. Going from 18 to 36 MP isn't. We're at the point of diminishing returns now - especially as lenses and physics are now becoming limiting factors, and virtually no-one needs to print anything that big and that detailed. If you really do, a larger format than APS-C will yield more real life improvements at such high MP counts. Marketing is leading this drive into the unneeded.
There comes a point where making EF-S glass good enough to resolve such detail at the large apertures needed to avoid diffraction becomes unaffordable. We're already at the point where the 17-40L and 24-105L cost less than their EF-S counterparts.
Which counterparts are you thinking of?
10-22 and 17-55. Admittedly, the 10-22 does have the 17-40 beaten when it comes to detail at larger apertures in the corners, so to call the cheaper L lens comparable is debatable. But the 17-55/24-105 comparison is a good one. The 24-105 when used on FF goes wider, longer, offers more detail, is brighter (f2.8 on crop = f4.5 on FF), and (at least in the UK) cheaper. OK, its vaguely bigger and heavier, but you can't have everything...