Film is dead. Long live post-processing! All the filters we’ve collected over the years can be trashed. Anything we used to do by screwing a piece of glass to the end of our lens can now be reproduced in Photoshop. Right? Not quite.
What’s So Special About a Polarizing Filter?
One filter that can’t be replicated in software is the polarizer. I’ll explain more in a bit, but first, what is a polarizer? Without getting too technical (I’m a photographer, Jim, not a scientist!) light produces glare as it reflects off glass, water, damp foliage, vapor in the air, and other reflective surfaces. This glare creates hot spots and washes out (desaturates) color. By using a polarizing filter you can remove most of the glare. So, if you’re photographing a lake, you will be able to see into the water rather than being stuck looking at the sun bouncing off its surface. Fall foliage will be richer in color. Blue skies get bluer and clouds pop out of the sky with increased contrast. Just about any sunlit outdoor scene will look better with a polarizer.
Choosing A Polarizer
There are a lot of options when buying a filter, so here’s what you need to consider:
- What’s the best brand? There are a ton of filter manufacturers out there. I use Tiffen filters because they give the most bang for the buck. Popular high-end brands include Hoya, B+W and Heliopan.
- Circular or linear? These terms have nothing to do with the shape of the filter (they’re all round), but indicate the way they do their job. For any automatic camera, you’ll need a circular polarizer. A linear polarizer will prevent the autofocus from working properly
- Filter Size. This is an easy one. Get the size you need for your lens. Most lenses have the filter size etched on them with a symbol that looks like a circle with a line through it, such as ø72 to indicate a 72mm filter size.
- Glass or plastic? As far as I know, all polarizers are made with glass. Forget plastic. You don’t want to put a cheap filter on your expensive lens.
- Filter Thickness. For wide-angle lenses, you’ll want to pay more and get a thin polarizer. The thicker ones are fine for longer lenses, but will cause vignetting (darkening of the edges) when used at wide angles. Or, save some money by fixing vignetting in Photoshop or Lightroom.
- Other options. There are combination filters such as warming polarizers. I recommend staying away from these expensive specialty filters. You can warm up the colors via your white balance settings or afterward in the computer. There are drop-in filters designed for really big lenses – like a 600mm. Most travel photographers will only need the screw-on filters since we aren’t the type to lug around this kind of huge glass.
How To Use A Polarizing Filter
The polarizer consists of two pieces of glass, so that once it’s mounted on your lens, you can turn it to dial in the amount of polarization you want. Aim the camera at your subject and turn the polarizer until you get the effect you’re looking for. The effect of the polarizer will be easy to see on a bright sunny day. On an overcast day the polarizer will have a reduced effect or no effect at all. Indoors or at night, you’d only want to try a polarizer to reduce reflections when shooting through glass. Everytime you point your camera in a different direction or turn it from vertical to horizontal, you’ll need to readjust the polarizer. Fortunately, this is easy to do – and well worth the effort. Since the polarizer reduces the amount of light reaching your sensor by about one-and-a-half stops, your exposures will be longer. So, when you don’t need it, remove it.
Why Software Polarizing Filters Don’t Work
Nik Color Efex Pro 3 provides a well-respected collection of software filters and effects for photographers. One of those filters is called “Polarization.” Nik Software describes their filter this way, “Simulates the color contrasts of a conventional polarization filter. Use this filter to enhance blue skies and other similar colors, while increasing the contrast throughout the rest of the image.” Notice that they don’t mention glare or reflections. That’s because this filter, as sophisticated as it is, cannot detect glare in an image. It only affects the contrast and color saturation. If your image contains an unwanted reflection, it will still be there after processing with Nik’s Polarization filter. Don’t get me wrong. The Polarization filter in Nik Color Efex Pro 3 makes a nice addition to your photographic toolbox as do most of the other filters in Color Efex Pro. Want to try them yourself? Download Nik’s free trial version at NikSoftware.com. When you’re ready to buy, get the best prices on Nik software at Adorama or Amazon. With the purchased version, you have the option to install Color Efex Pro 3 as a plugin for Photoshop or Lightroom.
- Don’t wear polarized sunglasses when looking through the viewfinder. You won’t be able to see the true affect of the polarizer.
- Be careful about using a polarizer to photograph through windows. Some windows, such as those in airplanes, cars and buses include a layer of plastic. A polarizer will cause strange psychedelic rainbows in your photos as it interacts with the light coming through that plastic.
- When using an ultra-wide angle lens – wider than about 24mm – the sky might change color across the frame from light blue to dark blue. This can be evened out in Photoshop. (Select the sky, add a “color” adjustment layer using a dark blue color selected from your existing sky. Change the blending mode to “darken” and adjust the opacity of the adjustment layer to make the sky look more natural.)
- Its hard to use a lens hood because you can’t reach the polarizer to turn it without removing the hood. I like to use my hood as much as possible to reduce stray light and improve contrast, so I find myself repeatedly removing the hood, turning the polarizer and, then, reattaching the hood. On one of my lenses, I’ve replaced the stock hood with a folding rubber screw-in hood. With that lens, I can turn the hood and the polarizer turns with it. This is very handy as long as I remember not to turn the hood so far in one direction that it comes off.
- The polarizer absorbs light – the more polarization, the less light reaches your sensor. So keep an eye on your exposures to make sure you don’t introduce camera shake.
- You can’t use a polarizing filter when creating a stitched panorama that includes sky. As you move the camera across the sky from one frame to the next, the sky color will change making your panorama less than seamless.
- You won’t want to use a polarizer when photographing fast moving action or wildlife. You won’t be able to adjust the polarizer fast enough as you pan across the scene.
- Because the polarizer absorbs a lot of light, it can be used as a neutral-density filter to get longer exposures in bright daylight when photographing waterfalls and such. If you do this a lot, a real neutral-density filter should be in your camera bag too.