CPL before or after other filters ?

didjiton

Hi all

First post, although have been lurking for a while, great forum & loads of helpful info.

I'm looking to buy a screw in CPL, I've been looking at B+W ones as they seem to be highly recommended. But notice they do not have a thread on the front. Meaning I could not attached a Cokin P holder. Is this a problem ?

So before I decided which CPL, does it matter if it sits before or behind ND grads? :scratch

Hopefully this is not a daft question but hey I need to learn.

Thanks

Robinivich

You're probably looking at a "slim" circular polarizer, basically with CPs the mechanism to rotate the filter takes up more space than usual, so to avoid vignetting on wide angle lenses, they make slim versions that sacrifice the front filter threads to avoid blocking light in the corners of the image.

If you mount a cokin filter system on the front of a CP (regular thickness, with front threads), you won't be able to easily adjust the polarizer without spinning your cokin filters around, this might not be an issue, as I don't know the cokins myself, but you might find that the two of them don't work together that well, I'd go for just the CP or just the cokins, as they can both selectively darken the sky, the cokins will be more easily controlled, but can't affect light like the CP can

:Edit: I forgot, Welcome to the forum!!!!

claudermilk

Yep, that's the slim version. Depending on what you're shooting with it is likely that going with the more expensive & less-convenient slim is not necessary. Hint: if you are using a 1.6 crop camera you won't need it.

There's a couple of solutions to the CPL + GND combo. One, you can get the Cokin/Lee/Hi-Tech style CPL that fits in the adapter and skip the B+W. Or, two, you can just hold the GND in front of the lens without using the holder.

didjiton

Thanks for the info both, your right, I am looking at the slim ones, mainly as I'm about to hook myself up with the Sigma 10-20mm (designed for APS-C so the 1.6 crop factor would not save me here, if think) and figured vignetting would be an issue at it's widest, especially if used std size screw-in and with the cokin WA (wide angle holder) on the front. I already have a cokin system (but not the CPL). The main reason for wanting a screw in. Is that I would like to able to use the cir pol, without having to attach the cokin holder.

I don't think adjustment of the CPL & Cokin is an issue as I could hold the cokin with one hand while turning the polariser with the other. As this set-up would only be used on a tripod. And you thought I had 3 arms

I've also answered my own question following a little more research. It does not matter if you polarise the light before other filters as the LEE system or after like the Cokin.

P.S - Thanks for the welcome.

Robinivich

As far as avoiding vignetting on the sigma 10-22, I don't know what thread size your current system is for, but one idea might be a step up ring, that would let you mount a larger diameter filter, if I'm not mistaken 77-82 or bigger. Upside, more room to work with all that junk hanging of the front of the lens before vignetting occurs. Downside, bigger CP=bigger hole in pocket when you're done.

didjiton

Thanks, I'd considered the step-up ring option as my lens are 72mm one the Sigma 18-200 & 77mm on the 10-20mm. So I've decided to ditch the screw in option and went for a cokin cir pol which I can use on both lenses. It arrived today. Hope to get some shots this weekend, weather permitting.

Thanks for the advice.