Recently I had my very old Leica screw mount 35mm Summaron lens overhauled by Sherry Krauter in upstate New York. She took the lens apart and cleaned the elements and changed out the lubrication. The lens looks like new and I really wanted to compare images taken with it and the relatively new 35 Summicron ASPH. I was pretty amazed at what I got. The ancient 35 Summaron amazed me. This lens was built back in the 50's. I used a subject that was in shade but bright color wise. To my eye the difference is very minimal. All the images were taken at f 5.6. 

35mm Summicron f2 ASPH

Exposure ISO 200 1/250s @ 5.6

The contrast and warmer color temp of the Summicron ASPH can be seen in this image. 

35mm Summaron f3.5

Exposure ISO 200 1/250s @ 5.6

Not much of a difference with the Summaron besides being a little cooler and the contrast is just a little less. Pretty amazing to me.

35mm Summicron f2 ASPH Exposure ISO 200 1/350s @ 5.6

You can still see the warmer tone and better contrast in the Summicron image above.

35 Summaron f3.5

Exposure ISO 200 1/350s @ 5.6

This Summaron image is a tad darker but is cooler and with a little less contrast.