No offense Didger, but it sounds like you've never tried it yourself...
Hey, no need to keep "no offense-ing" me. I don't get offended over such things, only gratuitous personality slams. I know there's a lot I don't know and I haven't ever done any BD correcting, but only read about the image degradation thing.
That is probably the WORST way to try and deal with falloff!
Yeah, I wasn't too clear. I've occasionally done some doctoring of boring skies with cloud cloning and if a dark corner is involved...
Yours wasn't that.
I'll take your word for it. Several people suggested that in the thread, so I figured, OK, maybe. It must have been the 18mm lens, since the 28 and 35 have way way less falloff than that. In fact as you can see from my test results here, the 18 images have less falloff than the other picture. You'll also notice that the bottom corner falloff is less than top, which I've noticed before too, so why that image had such drastic falloff (though probably f11, and not f8 like the test strip here) is beyond me. The 18mm picture on my "suggestions" thread also had very mild falloff that only one person commented on because he thought maybe it was intentional, since he thought it enhanced the image.
In any case, the 18mm falloff I can live with, since usually it's pretty mild even before any correction and I don't see a problem with the 28 and 35mm lenses at all.
Sorry to burst your bubble
My photography bubble is made of indestructible material and has little to do with equipment; don't worry.
Anyway, I'd be interested to see what some 18, 28, and 35mm sky shots would look like with your Canon super lens. Resolution tests are not quite so easy to do comparisons with from different locations, but sky shot falloff tests are pretty simple, so how about showing us?