Pentax A*300/2.8 and CPL drop-in-filters

*Syb* · 02-01-2009, 08:46 AM

Hi,

This thread may look a little bit like the one about the FA*300/2.8, but this question is about the manual focus A*300/2.8.

The SMC A*300/2.8 lens has a rear filter slide with size 49mm. "Cool!" That is the same size as ther front of my FA50/1.4, I thought, so all my filters for that lens can be used in there, too.

True. But the CPL is too thick. Just cannot slide it in. That really is a pity, I'ld like to see how this lens performs with a polarizer.

Is this inconvenience dependent on the filter brand? Or will all polarizer filters be too thick? (Will a Linear polarizer do the trick? Or be too thick, too?)

Can anybody help me out?

Ben_Edict · 02-01-2009, 01:55 PM

A linear polarizer won't do anything for your problem. You must search for a slim filter, used for wide angle lenses. There are some polarizers available with around 3mm thickness (Hoya/Kenko and, if I remember rightly, also B+W) - these might fit. I had the same problem, when I needed a drop-in filter for my old Tamron 300/2.8 and searched quite a while...

Ben

*Ron Boggs* · 02-01-2009, 04:19 PM

If cost is no object, there are 112mm circular polarizers available, including the famous Kasemann Circular Polarizer. As I recall, they are about $400 from B&H. I used one with the A*300/2.8 and it worked very well. Already sold it to another forum member. I've never seen reference to a drop-in circ. polarizer for the A*49mm drop-ins--with the external wheel for rotating the polarizer. They exist for FA*43mm drop-ins--in silver color, and for M*67mm lenses for 6x7 format in cream color, but I've never seen the cream colored 49mm polarizing drop--ins.

Using slim circ. pol. in the drop-in will probably work fine, but it is a pain to have no simple way to rotate it from the outside. If trying to use it while following wildlife it will be difficult as the angle to the sun will change frequently requiring you to pull it out and reregister it (you may want to spring for a polarizer with the degree numbers around the ring--if they still exist and exist in slim configuration).