A Primer on Lens Filters :: Digital Photo Secrets

A Primer on Lens Filters

by David Peterson 1 comment

During the old days of film, the lens filter was an important piece of equipment. It was often used to balance colors or to add special effects to an image but today’s digital technology lets us set white balance manually, or make changes after-the-fact in post-processing. Is there still any use for those filters? If so, how can we use them? How can they help improve our photos? Now's your chance to find out.

What is a Lens Filter?

A filter is an element made of glass, resin, polycarbonate, polyester or plastic material that can be placed in front of the lens. It modifies the light that enters the lens and can be used for any of the following purposes:

  • To reduce or eliminate glare on reflective surfaces such as water or glass
  • To enhance the saturation of colors in an image
  • To allow for a slower shutter speed during an exposure
  • To capture images with a high contrast range
  • To correct color balance
  • To produce special effects such as starbursts, motion blur, bokeh, etc.
  • To convert a lens for macro or close-up use
  • To provide extra protection for the lens

Some of these effects cannot be replicated with post-processing software, and in those cases the filter can be an indispensable tool for a budding photographer.

Types of Filters and Their Uses.

There are lots of different filters on the market today, each with its own important uses:

UV/Haze - Cuts down on haze and protects lens from dirt or dust. Can be used anytime, anywhere
Polarizing - Reduces or eliminates glare or reflected light. Used for shooting water, sky, or any highly reflective surface; darkens the sky and improves color saturation of outdoor subjects
Neutral Density (ND) - Reduces the amount of incident light and allows for longer exposures. Can be used to create a misty "angel-hair" effect in running water; allows slow shutter speed in bright light, which can be useful for panning or for removing moving subject/s from a scene
Graduated Neutral Density (GND) - Reduces the contrast of a given scene. Used in high-contrast scenes where the dynamic range between foreground and background is too broad
Cooling/Warming - Corrects color balance, removes color cast Used primarily with film cameras. Application is similar to the white balance setting on a DSLR
Special Effects - Creates optical illusions and effects. Can be used to add enhancements such as a starburst effect, motion blur, bokeh or a soft, dreamy look
Close-Up - Reduces the minimum focusing distance of a lens. Allows normal lenses to be used for macro photography

Choosing a Filter

There are a lot of different filters available, but the most popular and widely used for digital photography are:

1.UV Filter

UV light can cause a reduction in contrast. During the days of film you needed to have a UV filter to counter this effect, but today camera sensors have a built-in UV/IR filters. We still use UV filters but now they primarily serve as a way to protect the lens from scratches or dust. UV filters are not a perfect solution, however, and may introduce a slight color tint or reduce image sharpness. If you have a high quality lens and you want to protect it with a UV filter, it is best to get a filter of equal quality. UV filters can cause or exacerbate other image problems such as lens flare, ghosting or reflections, so as a general rule you should avoid those less-expensive UV filters if that's something your budget will allow.

2.Polarizing filter

If you take a lot of photos outdoors, a polarizing filter is probably the most useful lens filter you can buy. This filter will darken the sky and improve color saturation, and it can also reduce or eliminate glare and improve contrast. You can think of a polarizer as sunglasses for your lens. Use one to reduce glare when shooting through glass, water or other reflective surfaces.

There are two types of polarizing filters on the market: linear and circular. A linear polarizer is not recommended if you are just starting out as it will fool your camera's meter. A circular polarizer, on the other hand, has a second lens element, which means that it doesn't create the same problems. By rotating these two elements, the intensity of the polarizer can be adjusted with maximum polarization being achieved when the aligned elements are perpendicular to the direction of the sun.

Polarizers should be used with some caution--for example, when you pair one with a wide angle lens, it may create an unnatural and unevenly distributed darkened blue hue. And remember that a polarizer will reduce the amount of light that reaches your sensor by two or three stops, so you may need to shoot some scenes with a tripod.

3.Neutral Density (ND) Filter

The ND filter is popular with landscape photographers, but can be used in any situation where you want to reduce the amount of light that reaches your camera's sensor. ND filters are rated according to density, or amount of light reduction:

Density Rating F-Stop Reduction
ND102 ND 0.6 ND 4 2-stops
ND103 ND 0.9 ND 8 3-stops
ND109 ND 2.4 ND 512 9-stops

ND filters will let you slow down your shutter speed even in very brightly lit conditions, which can be particularly helpful if you want to pan with a moving subject or add motion blur to your image. They can even be used to remove people from crowded places—those super long exposures won't register any moving objects, only the static structures in a scene.

4.Graduated Neutral Density (GND) Filter

Graduated Neutral Density (GND) filters are also popular with landscape photographers. They work the same way as a standard ND except that they have a gradient from light to dark. The gradient between light and dark can be gradual, which will create a smooth or soft-edged transition, or it can be abrupt. This filter is helpful when shooting a dark foreground against a very bright sky or background. The GND filter allows foreground light to pass but filters the bright sky, which makes the contrast of the scene narrower.

Types of Filters

Lens filters come in two basic styles:

1.Screw-type or Circular Filters - This type of filter is circular and is screwed-on to the front of the lens. Make sure you purchase a filter with the same diameter as your lens—though if you do happen to have an incompatible filter, you can still use it by purchasing a step-up or step-down adapter ring.

2.Front Filter or Rectangular/Square Filters - This type of filter adapts to lenses of varying diameters, so you only need to buy one filter to fit all of your lenses. The filter is held in front of the lens or is placed on a filter holder. If you like the filter holder solution, you will still need to get one holder for each one of your lenses, assuming they all have different diameters.

If you’re new to lens filters and are thinking of adding one to your inventory, a polarizing filter or an ND is a good place to start. These filters will allow you to shoot in difficult light but can also be used to enhance your creativity and they're a lot of fun too.

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  1. kalyan das says:

    very much helpful to take a decision on filter purchase.

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About David Peterson
David Peterson is the creator of Digital Photo Secrets, and the Photography Dash and loves teaching photography to fellow photographers all around the world. You can follow him on Twitter at @dphotosecrets or on Google+.