What's interesting about the Hartblei PC 45 is the fact that the manufacturer (agent) publishes resolution statistics on their website
here They've used a very high resolution B&W film, T-Max 100, which apparently produces no noticeable degradation in contrast up to 50 lp/mm (ie. 100% MTF response at 50 lp/mm), and at 100 lp/mm, MTF response is still an impressive 60%.
However, the implication of these tests tend to indicate the lens could be a bit soft on 35mm format and
very soft on APS-C format such as the 20D, 30D etc, if in fact it is able to be used on such cameras. (I suspect the protruding built-in flash might get in the way of such a bulky lens).
Since the 5D produces images at f16 that are only slightly less contrasty (sharp) than at f8 (on most zooms), the Hartblei PC 45 might give reasonably good results on that camera. However, whilst f16 produces little loss of contrast on the 5D, f22 is clearly into the diffraction limited zone, producing images which clearly
are softer and less contrasty.
If you examine the resolution figures on the Hartblei site, you will see that resolution in the centre is the same at f16 and f22, ie. 55 lp/mm, which is greater than the resolution at f8. At 8mm from centre, f16 has the edge, but at 19mm from the centre, f22 has the edge.
In other words, your sharpest images from this lens should be at both f16 and f22, with f22 having the DoF edge of course.
However, one advantage I see over the Canon TS-E lenses, purely from the resolution aspect, is that the crop factor of 35mm format means you will not be using the eges of the image circle when using the Hartblei PC 45 with the 5D. One major criticism I have of my Canon TS-E 24mm when used with my 5D for stitching purposes (using shift) is a very noticeable resolution fall off at the outer edges, as well as strong vignetting. It's so bad, I've retaken some shots using my 20D from a greater distance to get the same FoV.
Of course, I understand that the main reason for getting a Hartblei is the greater flexibility of adjustments, but it woul be a pity if resolution had to be compromised in order to benefit from this greater flexibiity.
