First of all, the adapters. I buy the cheapest adapters from China, $6 and free shipping. I brush off the cheap black paint on front and sides, and polish them to a high shine to mach the beautiful lenses from the 50's and 60's. I use shims of brass, black plastic, black paper, and ultra thin rice paper. By varying the tightening I get into around 1/100mm in accuracy. Once a lens is perfectly calibrated at infinity and 30cm it stays on the adapter. 1 adapter per lens. I the loosen the set screws on the lens and rotate them so that markings are on the top. From start to finish I spend about 1-2 hours per lens. Now, this is just the setup. I think it is vital for street photography to have everything lined up right.
The test today was of lenses from Kern Paillard, more specific, the designs from Hans Schlumpf, and 2 Cosmicar lenses, and the 01 8,5mm Pentax Standard Prime as reference.
I will not post test images because of the limits in this forum, but rather give a description of my findings.
My test subject matter was a dummy my daughter made in a garden chair. I wanted a "real life" scenario to test DOF and center resolution. Almost all these lenses are made for a 3,5x4,5mm frame, while the Q7 that I used is almost twice that.
Findings:
Only 2 lenses showed vignetting from wide open, the IDEAL Hannover 6mm f.1.9, and the Switar 5,5mm f.1.8. I use them for square 1:1 imagery. When masked down and sized up to the Standard Prime (SP) 8,5mm, the IDEAL Hannover fell through in both resolution and contrast. The Switar 5,5mm was on par with the SP regarding resolution, but had better contrast and clearer colors and less bleeding into darks. The Pentax SP turned out to be a big disappointment compared with these tiny glass and metal lenses. Compared with the Kern Yvar 12,5mm f.2.5, the Kern Switar 13mm f.0.9 it is no good, even when distance was adjusted to match the field of view. The Yvar 13mm f.1.9 is not a good lens either, but a triplet design should never be made with a large aperture. It suffers on all apertures for this and is not recommended for other than "toy-like" effects. The Yvar 12,5mm f.2.5 is a fix focus design, and I have calibrated mine at 10meter. At f.4.0 it is sharper and more contrasty then anything I have seen. This was one of the three biggest surprises in my little test. The second was that the Pentax SP was so bad in comparison. The Switar 13mm f.09 isa fantastic lens in its own way. Only flaw is that it starts to vignette at f.2.0, (but then one can switch to the Yvar 12,5mm). A larger version (18mm f.0.9 for C-mount) was ordered by NASA for the Apollo 11 moon landing. The lens is super sharp in center at f.0.9, but low in contrast. At f.1.4 it is stellar, and covers the full frame of the Q7 with beautiful bokeh. The third surprise was the Yvar 36mm f.2.8. Even though it's just a triplet, the center piece of glass is so perfected by Hans Schlumpf that it has no CA what so ever. H.S. calculated the thickness and curves of the glass in order to have this exact effect. In resolution it is also better than its 8-element larger Switar 36mm f.1.8 brother. The only advantage the Switar has is the 1 and 1/3 larger aperture. To conclude: Yvar 12,5mm for landscape at f.4.0 to f.5.6, Yvar 36mm f.2.5 at 4.0 to 5.6 for landscape, the Switars 5,5mm, 13mm and 36mm for street and portraits, very good at all apertures up to f.5.6. Resolution takes a big hit on all lenses at f.8.0, but bokeh at edges are nicer.
The 2 Cosmicar lenses ar up for sale in a while. The 25mm f.1.4 is nice, but nothing near the Kern Paillard Yvar and Switar. The 6mm f.1.2 is a big CA joke, only suitable for experienced BW photographers as an alibi for making art
Here is a picture with Switar 13mm f.0.9 at f.0.9 of the dummy my daughter made for me. Full frame, no crop, on Q7. It has a certain amount of character, but it is super sharp in the center. It does not show here in the down-scaling, but it really is.
Oh, by the way, I tested the Kern Paillard because the were the best in the world at the time, and because I have become a huge fan of the mathematic genius of Hans Schlumpf. These lenses (the ones after 1955-56) are computer designed. Kern started to use computers at that time to test out theoretic design possibilities. The even had coating on their lenses as early as 1942. Ok. I'm a nerd. But it's very exiting