There are a few tools in my camera bag that are indispensable. Among them are a charger, spare batteries, flashlight, and a circular neutral density filter. All very important. But up there at the top of the list is the circular polarizer.

Back in the film days I carried quite a few filters. While most of those are now unnecessary, the polarizer is anything but. I won't head out into the field without it.

Ironically, the one function many people associate with polarizers (enhancing blue skies) is something that can be addressed quite easily - and arguably more effectively - in Lightroom.

Glare, though, is entirely different. You can do a lot of things in post-processing; erasing glare after the fact is not one of them.

Glare is almost everywhere. Your eye makes allowances for it; the camera doesn't. Use the polarizer to remove unwanted reflected light.

Eliminating glare enhances both color and detail. The polarizer knocks back reflections on wet rocks, wet vegetation and water. (Doing so can enable you to see things that otherwise might not be visible - like rocks laying on a shallow lake bed beneath the waterline.)

The accompanying photo was made in the Hoh Rainforest at Olympic National Park on a day when it was raining heavily. There was glare on everything: the bark, the ferns, and even the moss - but the polarizer removed all of it.

That said, this filter isn't just for drizzly conditions or when you're working at a water source. Reflections don't happen only where water is involved. Reach for the polarizer on dry days and when it's sunny, too. Shoot the foliage in autumn with it and the end result is a little bit like what you would have gotten back in the day with an enhancing filter. (If you never used an enhancing filter, it intensifies the saturation of reds, oranges and earth tones.)

In a pinch, the polarizer can also serve as a mini-neutral density filter. It'll remove up to two stops of light.

Indispensable!

It doesn't always belong on the lens, however. Sometimes a little reflection is desirable. In some instances there may be no photograph without it. For example:

Let's say you're shooting water lilies. Turn the ring all the way and the water renders as completely black - which can look very cool - but you'll also lose the reflections of the flowers. Dial back a bit to get the best of both effects. You can also make two photos: one which removes glare from the plant and the other with no polarization for a beautiful reflection. Combine them in post.

If the subject is a rainbow, the polarizer isn't your friend. Rainbows, as you'll recall from long-ago science classes, are created by reflected and refracted light. No reflection, no rainbow.

Finally, if reflected light augments the scene, obviously you don't want to eliminate it. Warm light hitting wet rocks along the ocean at the beginning of the day might tint them in a dramatic way. The ocean might also have taken on a lovely cast. Your polarizer will remove some of that wonderful color.

There's a time and a place for everything.

A final note: when shopping for a polarizing filter, go for the gusto. It'll be spendy, but this thing will be a workhorse. You invested in good glass; get a quality filter. If your lenses don't all have the same filter thread size, save some money by using a step-up filter ring.

Stow it in your bag and never leave home without it!