ND's and CPol's

Can I use two Circular Polarizers to emulate a range of Neutral Density filters?

Yes. In the sense that you could attach a hose-pipe to your nose in order to emulate an elephant.

Simpler to buy a ND filter. Or three.

G

They would be very dark! Polarising filters alter colour too, ND's are designed to have minimal impact on colour. You might get some strange effects from the polarisers as they rotate and go into "extinction" (total opacity)

George - it must be the air in the Isle Of Man

Mike

We don't have air. We have hundred mile an hour pure ozone.

G

Since I own a CP already and am getting a bigger one for my 16-45mm, I will already own two of them.

So in my case it's not simpler...

And no, I haven't forgotten about the stepping rings...

And my understanding was that when a CP is oriented a certain way, it has no effect whatsoever other than to darken the image the same way an ND2 would. So one would conceivably be able to orient the two CP's wrt one another to achieve the correct/desired "darkness", and then orient the assembly wrt the sun in order to achieve the desired effect (or lack thereof) on the scene. :

Yes?
No?
Three bags full?

George,

I could do with a few bottles of that right now.

Mike

I'm afraid in the vast majority of cases this can't happen.

some physics -For the purposes of a polarising filter, light travels as a transverse wave. When these waves (from the sun) hit a surface the angle of particle oscillations that make up the wave changes, and changes differently for each surface/angle of surface. A polarising filter works by only letting through light waves in one plane of oscillation. i.e it'll make the scene darker, but have a different (sometimes undesirable) effect on each part of the scene.

No.

An ND filter reduces all light passing through it. A polariser, on the other hand, only cuts light in a particular plane, and has a very different effect. It is most well-known for cutting reflections from water, and darkening skies whilst leaving the brightness of clouds unaffected.

In both these cases, an ND filter would simply darken the scene.

They are totally different things.

G

RTFL@ George

The 2x polariser trick only works if at least one is a linear polariser. Two circular polarisers will do almost nowt

ND filters & ND grads are easy enough to come by... somewhere like Speedgraphic or SRB Film are good places to start. Or search out a second hand camera place. Cokin A filters are generally very easy to find and cheap.

Matt

I shall experiment and advise findings... eventually...

Thanks all

HAHAHA

VERY funny George. (sorry for the delayed comment but I'm almost half a world away from you)

At first I thought you were joking but obviously IT WORKS!! Do you think this combination of Linear and Circular would do the trick?