@cirwin2010 excellent summary, thank you for sharing. I agree with absolutely everything, except maybe your assessment of the 55mm lens.
My biggest issue with that lens if flare and the need to always carry a lens hood, which is quite awkward and bulky for this lens. Speaking of sharpness, I find it pretty sharp. This is my lens of choice for indoor use, and I shoot it mostly wide open. Here's a 100% zoomed fragment of a 6,000x6,000px scan. Wide open, slightly off-center:
View attachment 310612
Perhaps there's variability between copies, or maybe my standards are lower than yours
As yes, the lens hood is definitely needed if there is any chance of light sources skimming the front element. That does negate some of the size advantages of the 55mm lens and the TLR lens hoods are note as convenient to use as on other systems.
When I first got my camera with the 55mm lens, I shot a roll with my camera point up close to the brick of my fireplace. I did this test to ensure that my plane of focus looked good and to assess the performance of the lens. Many lenses don't perform well when focusing at their minimum focus distance/up close such as in this instance. This may be a worst case scenario for the lens. These are my findings and are entirely subjective:
f/4.5
Center: Resolves enough details to be acceptable for smaller enlargements (4x), but soft when looking closely or under a loupe
Edges: Very soft, no edge to edge sharpness
Vignette: Strong and very noticeable
f/5.6
Center: Getting sharper with improved contrast. Good, usable detail for small to mid size enlargements.
Edges: Noticeable improvement from f/4.5, but still soft
Vignette: Improvement over f/4.5, but still noticeable
f/11
Center: Very sharp with great contrast. Have made good enlargements up 7-8x with good detail. For my landscape work I consider this my working aperture.
Edges: Very sharp. Softness is gone
Vignette: Gone
The 55mm is a good lens, but I believe some of the behaviors I've observed may be due to lens design constraints. Most wide angle lenses tend to get bigger with larger front elements, but the TLR is very space constrained due to the presence of a neighboring second lens. Its possible that there is variation between copies, but I definitely have high standards since I like making highly detailed prints up to 16x20". On my lens, shooting at f/4.5 might be cool for creative effects, but I haven't really tried that yet.
As a side note, the RZ67 50mm f/4.5 ULD lens is one of the most impressive lenses I've ever used. Downside being it is large, very expensive, and the camera system as a whole is not very portable.