When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. According to a reliable rumor source (thank you!) Canon is testing prototypes of the following DO super telephotos; RF 400mm f/3.5 DO IS USM RF 400mm f/4 DO IS USM RF 500mm f/4.5 DO IS USM RF 500mm … Continue reading New rumor of Supertelephoto DO’s and the R1 [CR2]