It's an open secret that many compact cameras are produced by OEMs - companies that produce large numbers of products that are then sold under other brand names. Tamron, for example, builds lens/sensor modules that form the basis of many compacts. Companies such as Asia Optical and Sanyo DI Solutions build compacts that are then sold under a range of brand names. The practice isn't confined to compacts, though, with distinctly Tamron-esque lenses appearing in big brands' lineups, for example. But we were still surprised to read about Sigma's latest patent for a 75mm F1.8 prime lens...

The patent, highlighted on the egami blog, shows the details of a 75mm F1.8 prime, specifically designed with a lightweight internal focus element to allow fast focusing for stills and movies. That's a combination of features that sounded somewhat familiar.

Sigma's patented 75mm F1.8, 10 element, nine group lens design
The 10 element, nine group design used in the Olympus m.Zuiko 75mm F1.8

And, while that could be because it's essentially a text-book definition of how to design a high-quality lens for contrast detection AF systems, a look at the optical formula diagram offers more convincing evidence to support the idea that Sigma designed the Olympus m.Zuiko 75mm F1.8 - one of the best lenses for the Micro Four Thirds system.