Does anyone know what differences (if any) there are between the ISCO IIIL and the 4XL? The 4XL looks to have the focusing ring is a bit further back, but are there any differences optically? Or are the ISCO IIL, ISCO 4XL, and Schneider Cine Digitar 1.33XL basically all the same lens just with different cases? Searching has not turned up much info unfortunately. Thanks!