photoman022 Loc: Manchester CT USA

i wouldn't do it myself but i can't argue with the logic involved in the very first reply!

whitewolfowner

So put the ND filter in the front! WOW, that was really hard.

alandg46 Loc: Boerne, Texas

It can be difficult to remove the stack if the polarizer is on the the bottom

Meganephron Loc: Fort Worth, TX

As several posters have said, put the polarizer on last in a stack. FIRAT IT WILL BE EASIER TO STAK THE ND and polarizer. It will be easier to remove the stack and in stack the filters. And finally, it is easier to set thee polarizer as you know it's the last element instead of fumbling around for it. Twist a whole stack to set a polarized mounted first could damage the filter or camera's mounting ring.

fetzler Loc: North West PA

No problem. Two filters should not be a problem. You can have some issues with vignetting on super wide angle lenses and a very slight reduction in image quality as there is more glass.

jcboy3

It always depends on what you are trying to achieve. Slower exposure times; use an ND. Reduce or kill reflections, use a CPL. Do both, use both.

That said, you will want to put the CPL on first, adjust it for effect, then add the ND filter and adjust exposure. Of course, you want to ensure the CPL filter is in the original position after adding the ND filter. I use a silver Sharpie to place some marks on the outer ring of the CPL. It's easy to see where those marks are after adjustment, and return the filter to that position after adding the ND filter.

Note, I'm not saying to do the marking for this exposure; just having some marks for reference makes it easy to return to approximately the same position.

As an alternative, you could use tape to lock the CPL in place; piece of gaffers tape would do the trick. That's just another thing to fiddle with, which is why I just marked up the filter.

The marks can be easily removed with alcohol or goo-gone, if you decide to sell your filter in the future.

lamiaceae Loc: San Luis Obispo County, CA

Wow, you really got some vignetting there (I assume you posted it to illustrate a point). I have the same lens* but use it on a K-5 and K-20D. I really hate CPL and ND filters. I often use my vintage "film" K, M, A, FA smc-Pentax, and M-42 smc-Takumar lenses and find they have more contrast and saturation than newer DA and DA* lenses so I don't need CPL filters for deep saturated blue skies. And w/o the filter the skies are much more even in tone. But, yes, "oversized" filters would eliminate the vignetting problem. Also for this shot, stepping back a little (@ 16mm) and cropping you could get the same shot w/o the black vignette. Or as stated, shot at @ 21mm. I'd probably only find use for graduated N.D. filters in my photography.

* I have an early bought new copy of the smc-PENTAX-DA* 1:2.8 16-50mm ED AL [IF] SDM lens and it came with a defect in the SDM motor. Pentax never admitted the known defect in many of the early production lenses. So I "fixed" the problem myself by hacking the lens' firmware and making it now always use the in-camera body focusing worm-gear. I don't have any smc-Pentax D FA (FF) lenses (yet).

Peace,

jcboy3

Or using a step-up ring and larger filters. Many ultra wide angle lenses are marginal at the widest angle; a second filter will likely vignette.

alandg46 Loc: Boerne, Texas

No kidding

jcboy3

Nope, not kidding.

rcdovala

A ND filter will not reduce reflections from water like a polarizer will.

wesm Loc: Los Altos CA

B&H has these: Formatt Hitech 100mm Firecrest Filter Holder Kit
The cpl comes integrated into the holder, and you put the ND filters in the brackets in front of that.
You can of course remove the CPL.

amfoto1 Loc: San Jose, Calif. USA

If they are both very high quality, multi-coated filters, should work fine. In fact, it's a common technique to do so, when the ND filter alone isn't quite strong enough... Or when wanting both to reduce light (ND) and cut some reflections or glare (C-Pol) in a scene. ND filter alone can't do that. OTOH, there are times when you don't want to reduce reflections because they are an important part of the image', so will want to avoid a C-Pol.

Test on your lens to see if you have problems with vignetting when the filters are stacked.

I also wouldn't use a "Variable" ND in combination with a C-Pol. Variable ND are essentially double stacked C-Pol and are already prone to uneven effects... adding a C-Pol to that would probably make for even worse unevenness issues.

Contrary to an earlier response, there's no problem adjusting a C-Pol when it's stacked with another filter.

Photogirl17 Loc: Glenwood, Ark.

I've shot smooth water without a filter also..lol It was dead calm out that day, and the light was just right.

Photogirl17 Loc: Glenwood, Ark.

Thanks for the suggestion, I'll check it out.