Is there a difference in the image produced from a 50mm rangefinder or slr lens?

Question

Particularly, I am interested in the performance on film for Canon leica thread mount (LTM) 50mm lenses versus their FL/FD SLR lenses, in aperture size 1.2/1.4/1.8. Their performance on full frame digital bodies like the A7 may also be valid with respect to things like sharpness, contrast and bokeh.

The main motivation for my question is the difference in prices these lenses commandeer on the used market, you can get a 50mm 1.8 SLR lens for less than $50 but the LTM one is usually three times as much.

Given that most of these lenses are probably six element double gauss designs, is there any intrinsic property that makes the LTM worth more/better than SLR version? For example, from this link, I quote this about the 1.4 LTM:

Impressive image quality for a basic design (I have found this lens better at f/1.4 than my copies of FD SCC, Takumar 7 and 8 elements, Minolta MD 50's)

What can be said about the comparison between the Leica Summicron f2 vs Summicron-R? Or the Zeiss planar 50mm f2 versions made today for DSLRs vs Leica M mount.

Answer 1

TL;DR I am afraid that you need to evaluate the lenses individually.

Rangefinder an DSLR lenses are often different in construction because both have different design goals and restrictions. RF lenses are often made to be smaller. RF lenses cannot be used from very close proximity, so no corrections or compromises for very close range are necessary. RF lenses, especially those intended for use with film, can have the rear element placed very close to the film/sensor. So these are often different constructions and therefore there will be differences. Since you ask about performance on a mirrorless digital camera - wider angle lenses (usually under 50mm) designed for RF can have reduced performance on digital cameras due to proximity of the rear element to the sensor and the oblique angle under which the rays reach it. Notable exception here is Leica M with sensor design that can handle that for all but very extreme cases.

The price differences between used RF and SLR are most likely commanded by the demand, but there is one technical difference that could support higher cost of RF lenses - rangefinder coupling. When you turn rangefinder lens, it's exact focusing position needs to be mechanically transferred to the camera rangefinder. This needs to be very precise and requires precise manufacturing and occasional corrections.

Summicron M and R - there are many types designed by different designers across several decades with different technology available at that time. where construction is identical between R and M (1976R and 1979M) so is the performance and character.

Modern Zeiss Planar - RF version is an f/2 and SLR version is an f/1.4. Different designs, different performance, different character.