What do you mean with “also blurry with Corona Bitmap”? Only Corona Bitmap is blurry, native C4D bitmap is sharp. (Keep in mind, there is a bit jpg compression visible)
And I think this issue is only with Corona bitmaps, I haven't seen this with C4D bitmaps...
/// EDIT
I made a better scene. Left side is native C4D bitmap. Right side is Corona bitmap. Again, please keep in mind that there is jpg compression, and my texture is not perfectly sharp.
Focal length is 15, 36, and 80mm.