lens hoods

I know it's a newbie question, but I am a newbie.

On both lens hoods of hte pentax kit lens for k10d, there are removable section.

The only thing i can think of, is that it is for ring flash cable.

Can someone enlighten me please?

It's so that you can rotate a polarising filter.

G

It's removaeable so that you can rotate a polarising filter with the lens hood still in place.

You even got replies in Stereo!

Now there's clever!

Thanks peeps, now I need to buy a polarizing filter!

Be sure you are buying a linear polarizing filter because you don't need to rotate a circular one.

Absolutely not correct. (But maybe you were joking... but just in case someone gets the wrong idea...)

Both circular and linear need rotating. The linear polariser will stop the autofocus from working. You need a circular polariser.

Matt

Can I buy a square one and stick it in my cokin square filter holder thingy and twiddle that a bit?

Of course - just rotate the whole holder
But... it doesn't work if you want a polariser AND an ND-grad. Then you need either a round polariser, or stack two holders together (Lee filters can do this, not sure about Cokin).

Matt

Yep. That wasn't a good joke.

(It's just there are all kinds of people who read here - I don't think they'd appreciate buying a linear and finding they can't focus )
Matt

I can stack a few filters together with the cokin system, but not separately, so if I rotated the polariser, the ND filter would be in the wrong place.

But I could try using the camera upsidedown.

AJ,
The Lee one is this:
http://www.leefilters.com/CPTS3.asp?PageID=134

You then have two filter holders with the front one connected to the rear - the front can then rotate independently.

Upside down sounds good though...
Matt

I looked at that one, and can't afford it and can't justify it's use yet anyway.

I've got a cokin filter holder and one ND filter. I looked at circular filters but for graduated ND stuff I wanted to be able to adjust the filter vertically.

The only thing I'm wary of, is increased vignetting by adding so much in front of the lens. I've seen a tip to cut off the outer sections of the cokin holder so only one filter is in place.

For landscape shots I'm thinking I only need an ND grad and possibly a polarizer (depending on how wide the lens is). is this reasonable?

AJ,
That's reasonable. Cokin and Kood do a round circular polariser for the Cokin P holder. It fits between the lens and the first filter (you'll notice the P-holder has the first notch slightly wider).

With the 12-24mm you can just about get away with using the P-holder with a tiny amount of vignetting on the corners. It becomes more obvious if the holder isn't at 90 degrees to the camera. (It's also the aperture of the filter holder that gets in the way - a friend of mine filed his out to make it slightly larger)

Even with the Lee and Cokin X-Pro you can get some vignetting at 12mm if the holder isn't at 90 degrees!

But yes, for landscapes, a polariser and one ND grad should be ok. If you add more than one Cokin/Kood/Hitech filter you'll get magenta tinges appearing

Matt