Lens filters are one of those items that salesmen like to push when a customer purchases a new camera. This is not new technology for they have been used by camera enthusiasts and pros for decades. But today we live in the age of digital cameras and are they even needed and they are merely another useless thing that salesmen up-sell to pad their commission?
First off, let’s discuss what filters are . They are merely glass or plastic elements that usually screw on to the end of a lens. And while a filter is not lens specific, generally, you will have to buy a different set of filters for since they are sized to a standard diameters and lenses can vary in size. Telephotos often take larger sized filters than wide-angle lenses do. I was fortunate in that my 50mm prime lens uses the same size as my 18-55mm lens.
There are several types of lenses and one of the most common is the Ultra Violet filter. Ultraviolet light, such as found in sunlight, can create a haze to the photos and protecting images from degradation is very important. In the old days, a physical UV filter was the only way to protect the image but today such protection today is superfluous because modern lenses come with a coating that provides the same protection as a physical UV filter. While one might think that doubling up would provide twice the benefit but a physical filter yields no additional benefit in matters of UV protection..
So, in this day and age, why would photographers affix them to their lenses? Protection. These filters act as a buffer taking the scratches and bumps instead of your more expensive lens. The more you pay for the lens, the more inclined you feel about protecting it, especially when you start shelling out four figures for some of the sweet glass. It seems like a no-brainer, everybody should be using UV filters on all their lenses. After all, a UV filter is relatively inexpensive and may save your lenses from expensive, if not fatal, injury. Well, there are a couple reasons not to use them for this purpose. First, any additional piece of glass you put in front of your lens will affect the quality of any images you take. While the effect may be minimal, a number of people believe that the degradation of the image isn’t worth the potential cost to image quality. Secondly, if you stack too many filters it creates a vignette effect that is usually unwanted. (Yes, Virginia, a vignette, done properly, is desirable thing). Personally I do not use a UV filter. As mentioned in a previous post, I utilize lower-cost kit equipment which makes me less sensitive to damaging my equipment. Also, If I did significantly damage a lens, the provides an excuse to upgrade to better lenses.
Another type of filter is a colored filter. If you grab one of these and hold it to the light you will notice that this filter changes the color of light passing through. There are a variety of reasons for this modifying light color, but usually it is to either correct the color of the scene you shoot, or it is to shift the colors to something more pleasing. For instance, incandescent lights produce an orangish color cast ,and in standard mode (or normal film), the whole scene takes on that orangy cast. By applying blue filter, the photographer magically changes that orange light into normal colored light thus “normalizing” the scene. But there are times when a photographer will actually seek to change the cast away from accurate to create a pleasing effect.. This, especially when shooting portraits, that a photographer will want the skin to appear “warmer” than it does in that particular scene, and through the use of a filter, this can happen.
So, why wouldn’t digital photographers want to use this filter for correcting and modifying the scenes they shoot? First and foremost, unlike shooting with film, today’s photographers, can easily color correct the scene in-camera and, more importantly, when processing the files with the computer.So, like the UV filter, adding more glass on the end of the lens offers no benefit to the image and may, in fact, slightly degrade image quality.
Next we come to the polarizer, and more correctly, a circular polarizer. Like other polarized items (sunglasses, monitor screens, etc) this filters out all light rays except those hitting the lens at a perpendicular angle. This is very, very powerful because one piece of glass removes the glare off foliage, reduces reflections off surfaces (like water, glass and metal), saturates colors and darkens blue skies. This filter does block some light and thus requires some considerations. Generally ,this is not a problem since the filter gets its heavy usage on bright days so losing a stop or two of light isn’t a problem and may even be a benefit. The filter belongs in the camera bag of any person who photographs landscapes. The benefits this lens provides CANNOT be duplicated in Photoshop.
Neutral Density Filter
The last filters to discuss is the neutral gradient filter, which acts like grey-colored sunglasses for your camera. They block some of the light but they do not affect the color of the image. Why would anybody want sunglasses for their camera? Because when a photographer wants to use a larger aperture or wants to decrease the shutter speed and the scene is too bright to keep highlights from blowing out, these filters save the day.
There is also a spit neutral density filter in which only a portion of the filter has the gradient. In scenes, where the sky is very bright but the ground and subject isn’t, that sort of flexibility is needed. Instead of choosing to blow out either the highlights or the darks the photographer can get a proper exposure for both.
The only filter I use is the circular polarizer, the others were a waste of my money. There are a variety of opinions regarding lens filters and it serves you well to read what others say. The type of photography you do will determine the usefulness of the various types of filters. For example, if you one expensive lenses and you do rock climbing, then you may want to use a UV filter for protection. Before purchasing, do you research and take the money you save and spending it on products that will improve or aid your photography.