Quote Originally Posted by revdocjim View Post
According to my Pentax 645 SMC lens manual, the correct hood for the 45/2.8 is the RH-B70mm, which is described as a "slide over" type of hood rather than a screw-in. That explains the 70mm diameter. .
I checked with the Pentax Forums site to see if I had made a mistake but it clearly says that the hood type is RH-RA 70mm screw-in and in fact there is no place on the A lens(manual) for a slide-over hood The FA(autofocus) has a slide over hood type PH-RBC 67 bayonet but while I understand your reasoning why a slide-over might be 2mm more it is still called a 67 which is the lens diameter.

It is a puzzle why if the screw-in fits a 67mm lens it should be referred to as 70mm when the screw-ins for other sizes such as the 75mm lens with a filter size of 58mm are referred to as 58

It might simply be that the Pentax forum has wrongly used the word 70 when it should have said RH-RA 67mm screw-in.

So the correct hood for the A lens is clearly a screw-in but the 70mm remains a puzzle.

Thanks to the other poster for referring me to the 67mm hood on Amazon of which there is a collection. The key here is getting the right type for the 45mm lens which in 35mm terms is a wide angle of about 28mm and might need the petal type of hood.

The question is which kind of petal hood would prevent vignetting with a filter?

I know there are quite a few P645 users here and hopefully they might chip in with comments

Thanks all so far