...is 37.5mm in case anyone is interested. I wanted a rubber lens hood to help block put extraneous light from falling on the lens so I tried a 37mm (too small)... a 38mm (too large)... finally found a 37.5mm B&W that fits perfectly. Maybe this will help save others from the trouble of looking. BTW, I use a Lens Baby lens cap over the lens shade front threads because the inner squeezers are easier to get to than the type with the outer squeeze tabs.
I searched all over the internet and even the L-778 manual didn't have this info... frustrating. :rolleyes: