This lens was made by Cosina with a very limited production run in the mid 2000s. It is an apochromatic prime lens that can focus very close: 0.5 m (although it is not a true macro lens). The 90mm lens is the most common and cheapest out of the three (90mm f/3.5, 125mm f/2.5, 180mm f/4) Apo-Lanthars. The 125mm lens is the most expensive and can do 1:1 macro.

 

For the 90mm lens, there are two versions: the SL with the chrome bayonet and silver focussing ring and the SL II which is black. The SL II has an electronic chip for working with Nikon cameras (no autofocus though). These two versions have the same optics. There is another Apo Lanthar 90mm for M-mount and L39 screw mount, which have different optics.

 

I bought the 90mm SL lens for $362 on eBay in the M42 screw mount in near mint condition. They are also manufactured in the Canon EF and Nikon F mounts, but are somewhat more expensive despite being fully manual. The lens is very sharp even wide open, and reaches optimum sharpness around f/8. There is little or no lateral chromatic aberration thanks to its apochromatic design; but there is a small amount of longitudinal chromatic aberration. In extreme cases there may be some purple fringing. Distortion is minimal. The lens's biggest weakness is its propensity for flaring, and the lens hood is even rarer than the lens and usually goes for $100 by itself. The build quality of the lens is most excellent. The focussing ring turns 270 degrees and is perfectly damped. The lens extends a lot when focussing close. The frontal element does not rotate (obviously, since the lens hood is rectangular).

 

I am using the lens with the K&F Concept M42-NEX adapter, which is very solid -- no play, no vignetting, and the lens works perfectly. You will need an M42 adapter with a flange to keep the pin at the back of the lens pushed down.

 

 

I will be using this lens for still life, architecture, and landscape.