I acquired a box of Ektachrome 6121 film from a fellow member of APUG with the intention of using it as in-camera film. I shot some, and I now have the results in my hand. I figured that some of you may have sheets of it laying around, so I'm sharing my results with you all. It appears that with a Wratten 85B filter, this film's speed (in daylight) is approximately ISO 8. Without a filter (in daylight), the film's speed is about ISO 40. In daylight, with a Wratten 85C, the film's speed looks like it is about ISO 125. (I need to do more testing to be more confident about this) I will soon post up some pictures of my results for you to see. All shots were at f16 at 1/100 on a Sunny 16 day. In summation, this film looks like a pretty low contrast color slide film, but not too bad. However, it also has quite an impressive exposure latitude. If you have any of this film sitting around, give it a try. My next go with this film will be cross-processing it in C-41 chemistry.