Maybe it's just me, but trying to hold a grey card in one hand, press the WB capture button with the other without the whole rig shifting sideways is at best awkward. Considered white fins but remembered the Flex Seal I used on my DIY Kracken video light floats last year, so wondered about using it to paint my fins. Turns out the grey color white balances quite well compared to "real" white and grey cards. It's held up extremely well on my floats, but I'll have to make sure it doesn't start flaking off on the flexible fins.
Quick test shots: Manual WB from the card shown in each shot. First two are proper white and grey cards, the third, Flex Seal on a scrap of paper.
Quick test shots: Manual WB from the card shown in each shot. First two are proper white and grey cards, the third, Flex Seal on a scrap of paper.