These are three pivotal pictures from the West and Southwest sections of my American Drive-in Theater project. All done with my 7x17-inch Korona camera with my standard 305mm G-Claron lens. I've had a lot of trouble getting scans of these negatives to do what I want. There's considerable illumination falloff with this lens on this format (vignette) which usually isn't a problem with New England woodland scenes or moody, stormy landscapes. But the enormous skies filled with clean pure light that you see out west made a whole different situation, with the falloff definitely not contributing to the pictures. This was compounded by the fact that, despite the drought, there were usually a few faint wisps of cloud, and because of the drought in the summer of 2012, there were always some pale patches of smoke-haze from the wildfires raging everywhere around. These slight tonal variations interacted badly with the darkening of the picture corners. (Do click on one of pictures to get the larger, isolated view of the pictures.)
Fixing the problem in Photoshop proved annoying, because the effect varied depending on lens aperture and various camera adjustments, making a routine fix impossible. Then I thought about the elliptical gradient tool in Adobe Camera Raw. You can custom shape the ellipse in real time using vector-drawing handles, drawing it custom for each image in just a few seconds. You can change the feather, specify the effect inside or outside the ellipse, and for the effect you have nearly the whole suite of ACR tonal adjustment tools.
So, the procedure is to scan the negative in two sections, orient and merge the two files in Photoshop, then throw the switch to make TIFF files open in ACR instead of PS. Open the file into ACR and fix the falloff along with other basic tonal adjustments, then save the result as a .psd file. Then open the .psd directly into PS to take care of the inevitable dust cleanup (worst part of scanning), then use a Curves adjustment layer and a burn&dodge layer if needed to do the final tonal tweaking. At last, the results I've been looking for from these negatives.