Newbie here.
Can anyone simply explain to me the difference between 'A' Series
Holders & 'P' Series Holders.
I have a mixture of lense for numerous cameras but with only two lens
thread diameters; namely 52mm & 55mm. I have adaptor rings for both &
a holder. but I have no idea whether it is an 'A' or a 'P'. There's
no indication on the holder. How do you tell the difference? And why
does the intro on this site recommend using a 'P' Series?

Regards,
Jack