You got it right, but keep in mind two things. The lens has to be or has to cover FF. An aps-c lens (like the sigma) put on a speed booster would vignette. The flange distance of the original mount has to be long. This means you can use lenses for nikon f, sony a, canon ef,etc... mounts, but you can't use the original E mount lenses because they have a short distance. If the 16-35 and 24-70 are for example canon lenses than I think it would be a nice option as they would be "f2 lenses", or just about the same looking as if you were using them on FullFrame. I wonder if it's worth the hassle, is the asp-c mode that great? I thought the rollingshutter was too bad.