The first Summicron version closely followed the design parameters of the Summitar. This is a small, lightweight lens that you can slip into any camera bag, into a pocket, or even just leave it permanently mounted to your camera so that it’s always ready to shoot.
Screw Mount Ltm L39
It’s such a small lens that it makes a Leica M camera feel sleek and compact, though its perfect dance partner is arguably the Leica screw mount cameras – where it combines to create a truly slim, street-friendly shooting setup.
Radioactive Yellow Glass
The unassuming little 50mm Summicron v1 Collapsible Lens sets the bar high for sharpness but the radioactive yellow glass lens beats it at pretty much all directly competing aperture settings. Even wide-open, the f2 lens delivers incredible sharpness and contrast for such an ‘old’ lens, with sharpness only really dropping off a bit at the extreme edges and corners of the frame.
Main source of radioactivity is the use of thorium oxide as a component of the glass used in the lens elements. Its optical properties of high refractivity and low dispersion allow lens designers to minimize chromatic aberration and use lenses of lower curvature. The presence of thorium can cause moderate to severe yellowing of the lens elements.
Leica summicron 5cm lenses with thorium elements pose a negligible risk to human health. However, infrond of the lens is significantly more dangerous. At close range the surface of the eye can quickly be damaged by them, potentially causing cataracts and other problems.
Radioactive Yellow Glass Serial Numbers:
Open it up to f/2 and you can achieve great subject separation, background blur and low light performance without sacrificing too much sharpness. Stop down to f/2.8 and beyond, though, and you’ve got a tack-sharp performer that captures all the details you could ask for.
While it’s clearly not in the same league as the mighty Summilux 50mm f/1.4, under certain circumstances it can actually match its big brother for sharpness. And, at least anecdotally, it’s a far superior lens to the older Summitar version.