Well here is some food for thought
Now that Nikon has announced their first FF-body - the much anticipated D3 - many of the already existing lenses and esp. the new 14-24mm
and the equally new 24-70mm
come into special focus, because they can deliver an image-circle that is large enough for the brand-new 12MPix Nikon-D3-"FX"-sensor.
Putting aside the "FX"-designation as pure marketing-hype and using the FF-denominator instead so that everybody knows what we're speaking of here, there comes up an interesting dilemma
: How do you fully test a Nikon FF-lens (like my latest toy, the 50mm/f1.4) on a Nikon-body and do the lens justice?
Why should this be a problem? Well, if you put it on the D300, you can only test the APS-C part of the image-circle with a 12MPix sensor. But you really have no way of knowing haw sharp that little beast is in the FF-corners, don't you???
On the other hand, put it on a D3-body and you can measure to your hearts content all over the place, but
you only have a sensor resolution of a 5MPix equivalent on a APS-C sensor
Well, what can happen then? Ok, e.g. that nasty color-fringing on the APS-C-sensored D300 could completely disappear on the D3-sensor
... and later reappear on a D7-sensor...
So you'll never
get to know the real quality of that particular lens in toto (as the old Romans would have said). Even if you do a double test with both the D300 plus the D3 - you will never
know how the corner-sharpness of that lens really is! Maybe you'll be quite disappointed with the performance of the lens you so expensively bought, when Nikon finally comes out with that 25MP-FF (sorry "FX) sensor.
And no-one out there has a solution to this challenge! That's pretty crazy. So for the time being you just have to trust Nikon, that their lenses which are sharp on a APS-C 12MPix-sensor, also will be sharp in the corners on the up-and-coming 25MPix-FF-sensor.
Good luck, Nikon(-users)!
Canonites clearly have it better in this respect
Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews
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