Quantaray lenses were made by Sigma, Tamron, Sun Optical and Tokina. This lens was made by Sigma and performs like a Sigma Mirror lens. It is reasonably sharp if you can hold it steady. It has the typical ringed bokeh we see from mirror lenses. Contrast is surprisingly high. Color rendition is a bit cool. While it is not a Zeiss or even a Tamron in quality, it is still far better than most brands flooding the market.