Be Excellent To Each Other

"Polarization, a new game from Sid Meier..."

Right, obligatory childhood joke out of the way. I've just bought a Hoya circular polarizing filter for my Nikon D40x, due to me reckoning it'd be handy for those Nevada shoots of arid, blue skys and sandy scrub. I have never used a filter in all my life. All my sorry life. Anyone proficient in them? Any advice and does and don'ts?

(Also bought an Emmy the Great album, which is great. Planning on getting a Gorillapod in the US as well.)

They're fantastically useful at cutting reflections from non-metallic surfaces, boosting contrast and saturation and acting as a weak neutral density filter.

Remember with circular polarizers, you have to rotate the filter to vary its effect (it's like a grid, essentially, blocking certain frequencies of light, or some science shit*). You'll be able to see its effects through the viewfinder, so it's easy to see what it's doing.

Be careful if you're using a particularly wide lens, else you're at risk of getting an unevenly toned sky (the filter will polarize one part of the sky, but not the rest). It's an interesting effect, but not entirely desirable to have a strongly gradiated sky tone.

The effect is most prominent 90° from the sun. Remember to shield the lens or use a lens hood if the sun is in the front 180° to the camera, else you'll run the risk of lens flare and reduced contrast etc.

In short, though: have a play around. Look for reflections in glass and see how your filter affects them. Note your findings and show your workings.


*All light has a polarisation. Pretend for a moment that each beam of light is an individual sine wave travelling through space. The polarisation plane is the direction in which the light goes up and down, and it's at right angles to the direction of propagation.

Polarising filters are like combs, they only let light through where the plane of polarisation matches the gap in the comb.

Normal light has all sorts of polarisations, at random. Putting a filter in the way of this blocks some of the light (where the polarisation is different). This is why it works as a weak neutral density filter. Putting a second filter behind the first and rotating it so the direction is 90 degrees away from the first will block all light and turn black, although that's not useful for photography.

Light reflected from a metallic or watery surface all has the same polarisation, and hence putting a polarising filter in the way of that light and rotating it correctly can block the reflection. Suddenly, a pool of water which looks like a mirror without the filter will become transparent, and you can see into the water instead.

OK, I can only speak about this from a video point of view, but here's the beef in simple terms.

Polarising filters can help cut reflections, reduce glare and also make certain colours deeper.

A circular polarizer will rotate so you get the best effect relative to the light source. For the deepest blue skies you need to be facing away from the sun. Facing towards the sun the effect is minimized.

You can also use polarizing filters to see through glass that is reflecting alot of light. For example, speed cameras have polarizers on them so they can also photograph the driver (Chinnytrufax! - Ed).

They are also great around water and even snow.

Basically think of them as sunglasses for your camera.

But as you have a circular filter, you do need to adjust it for the best effect.

You rang, I came, with all the TRAPPINGS OF A MAN OF SCIENCE.

All light has a polarisation. Pretend for a moment that each beam of light is an individual sine wave travelling through space. The polarisation plane is the direction in which the light goes up and down, and it's at right angles to the direction of propagation.

Polarising filters are like combs, they only let light through where the plane of polarisation matches the gap in the comb.

Normal light has all sorts of polarisations, at random. Putting a filter in the way of this blocks some of the light (where the polarisation is different). This is why it works as a weak neutral density filter. Putting a second filter behind the first and rotating it so the direction is 90 degrees away from the first will block all light and turn black, although that's not useful for photography.

Light reflected from a metallic or watery surface all has the same polarisation, and hence putting a polarising filter in the way of that light and rotating it correctly can block the reflection. Suddenly, a pool of water which looks like a mirror without the filter will become transparent, and you can see into the water instead.

Now to hit Submit and discover someone has linked to Wikipedia. (pause) wow, got away with it.

You lifted that middle bit word-for-word from my original post, you cunt. You can't come in here, proclaim you're a MAN OF SCIENCE, and blatantly plagiarise the work of others!

I, for one, welcome our new history rewriting overlords.

And I think that conclusively proves that invented the polarizing filter.

Ta for that advice and the SCIENCE chaps. That 'at right angles to propagating source' thing made my ears bleed for a moment, be-ums being used to the notion of things not propagating at right angles, but with extra thunking all was well. Kudos to all.

Would you say that 28mm is too wide an angle for polarizing filters with that gradation danger? Reckon I'll get a lens hood anyway, and a UV filter just for default-main-lens-protecting duties.

And a gorillapod, natch. They look awesome. Cheers again!

Nope, 28mm is fine. On a cropped sensor, I was talking more 16mm or so (effective focal length).

Desirability of their use can split opinions as well. /gets coat.

I can't speak for photographers, but from my point of view it's nice to have eye popping colours if you are doing certain types of outdoor stuff. I did a shot of Hersmoncuex Castle last Summer that looked wonderful with the reds of the bricks contrasting with the greens and blues. Granted you can do so much in the grading afterwards but if you get it right when you shoot you can only make it even better afterwards.

I was joking about "polarising".

I have a couple of DV editor friends who spit nails every time they get given shot footage that's had filters applied while shooting.

With photography it depends greatly on how clear you are on what you want to achieve, but my rule of thumb for shooting digital is to keep it clean and optimum and do stuff in post. Mostly.

The thing about polarisers though is that you can't really achieve the same effect in post, and that's the beauty of it; it puts the thought process back in the taking-pictures stage, and slows you down, rather than relying on saving things on the computer afterwards. Of course, with most other filters, you're absolutely right!

Circular Polariser and Graduated Neutral Density filters are the only ones I carry.

edit: of course, everything varies for the different types of photography. I love the outdoors, so like to slow myself down and take as much time getting it right in-camera before tweaking it in post. Mind, my photos are still quite shit; I have so much to learn.

My Bi-polarising filter really has its ups and downs.

Depends. On the rare occasion I shoot for someone else I'll do one shot with a polariser and one shot without and give them the choice.

If I'm doing it for myself I'll either do two shots, or make a call on which I'll want. The editors are quite correct that it can be done in post, but if you get it right on location it will look far better in the case of a polariser.

I don't use other filters other than the ND filters that are built into the camera or my UV filter (which I always have attached). Pretty much everything else can be achieved in post.

That said, if you have filters, if you want to do a really good job and you know what you are doing then you should use them. The cameramen on Top Gear use filters combined with post. But everyone will be following the Directors line on that show so they get the overall look right.

Filters are a tool which should be properly used.

In case of hunger, don't try to eat it.
In case of emergency, don't break glass.