I mentioned this idea in another thread but only in passing. Having come across a nice book on camera and telescope optics and found the bit detailing Afocal Teleconverters/Barlow lenses, I had a thought. These are largely used for making the image bigger but without messing with the focus. However, I then noticed the opposite exists and seems to be called a focal reducer. Some of them seem to be deliberately made to reduce 35mm to DX. Now the issue I can foresee is that telescopes focus in a very different way to cameras and any slight differences in flange requirements can be very easily adjusted, unlike DSLRs. The reason I'm thinking about this is very un-DX like. There's always the talk of more 'reach' with an FX lens on a DX sensor. What I want is more light! So my 300mm 2.8 becomes a 212mm f2 on DX. It then occurred to me that a Speedbooaster FTZ would be quite fun on a Z50 or even more extreme on the CX J5 with FT1. I then the lightbulb moment.... Could I not just turn around a conventional TC1.4 for the same effect? Any ideas?