I'm getting more and more frustrated that Zeiss nor Voigtländer (Cosina) make a nice MF 28mm for Sony E-mount (full-frame), so I'm thinking of getting a Zeiss Loxia 2.4/25 when a good deal comes along. To find out if that focal length works for me, I took the only 24mm I have, an old Vivitar 2/24 in Nikon F mount, out for a spin. Its serial number starts with 22 so Kiron supposedly is the manufacturer. As so often with Kiron lenses, the diaphragm leaves are oily, allowing the aperture to close down to around f/8. Even at f/8 image quality isn't all that great, but it works surprisingly well in B&W.