One can certainly differentiate diffraction between f/4 and f/22 on the LCD screen of a D800E in Live View, assuming the target is sufficiently defined. Just put your camera on a tripod, focus on the target in Live View, and compare the image at f/4 and f/22 using the Playback/Zoom In button to view at maximum magnification.
There is no question but that the use of swings and tilts with view cameras can in many cases allow us to use the lens at a wider aperture and get equivalent depth of field, and greater sharpness, than just stopping down the lens. Diffraction is, as has been pointed out, a law of optics and just because it does not apply to one's specific kind of work does not mean that it does not apply at all in general view finder photography.
To differentiate the effects of diffraction between f/32 and f/64 on a view camera would be a tall order. On the other hand, the difference in depth of field is not all that great either if you compare f/32 to f/64. A better test would be to compare the effects of diffraction and depth of field on the extremes, say f/8 and f/64.
Sandy
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