The dawn of the age of digital photography has brought with it many technological advances and techniques that were unavailable to the average film photographer of 20 years ago such as High Dynamic Range (HDR) photography and all the power and intricacies of pixel manipulation that Photoshop provides. Digital photography also mitigates many of the problems that occur with traditional film photography such as the physical limits of the light sensitivity of film, correcting for white balance, etc. (I’m sure anyone who has switched from film to digital can think of at least 100 more examples).
However, with the transition to digital photography many photographers both amateur and professional alike are now relying too heavily on digital methods to produce their desired results instead of using what I like to call rule number one of taking a good photograph: manipulate the light to get as close to the result you want before the photograph is taken. Manipulating the light can mean a few things. Studio photographers have the luxury of creating the scene with the exact lighting they want but most amateur photographers, landscape photographers, photojournalists, and even event photographers shoot most of their work outdoors in conditions that are beyond their control. For these photographers the only way they can manipulate the light is through use of filters and flash guns or strobes. Most professional wedding photographers will tell you that being asked to shoot a wedding without a good flashgun is like being asked to shoot with only one arm. Filters, on the other hand, are a different story. Many digital photographers tend to under use filters except to simply protect the valuable glass of their lenses. Many digital photographers (maybe even you) view filters as an ancient technology that was important for film but is less needed for digital since the camera can do everything a filter can. This is flawed logic. Filters can be the difference between a good photograph and a great photograph.
Film and the digital camera sensors are alike in that they both record the light as they see it. The light passes through the lens, is projected on the light sensitive material and recorded. What is recorded is what I like to call light information. Once recorded, whatever light information is captured is all that the photographer has to work with. Digital cameras may have many fancy built in filters but they are only manipulating the available light information recorded by the sensor, and therefore “digital filters” will always be inferior to a physical filter because a physical filter actually manipulates the original light information before it reaches the camera’s sensor. Many photographers like to shoot in RAW format, which contains all of the information captured by the camera’s sensor. RAW files allow the photographer to have the most light information to work with and edit. This is why filters make a difference as they manipulate the raw light itself, which is about as raw as you can get, preserving all of the available light-information.
The most important filters that a photographer should own are as follows: UV or clear protective filter, a Polarizer, and a Neutral Density or series of Neutral Density filters. A UV or clear filter is simply a no-brainer as this will live on your lens at all times and protect that valuable front glass element of your lens. I have UV filters to thank for saving at least three of my lenses. It should be noted that most digital SLR sensors have a UV coating and thus a UV filter is redundant and thus a clear protective filter is all that is necessary to protect your lens.
Circular polarizing filters are the most important filters a modern-day digital photographer can own. Polarizing filters physically prevent all but a select type of light through. A more detailed article on how polarizing filters actually work will follow this one, but to keep it simple think of polarized light as a wave, much like a wave on a piece of vibrating string. These waves exist either oscillating up and down, left to right or anywhere in between. The angle of this oscillation is called polarization. Polarizing filters, just like polarized lenses on a pair of sunglasses, only allows a specific “angle” (i.e. up-and-down or left-to-right) of polarized light through the lens. Circular polarizing filters have a rotating front element on them which is used to control the angle of polarized light that is allowed to pass through the lens. By turning the front element of the filter a photographer can change how light appears to reflect off of any surface which can remove reflections, increase saturation and reduce or increase contrast. The polarizing filter also has the advantage of manipulating the look of the sky. These are all things that no software can possibly reproduce accurately. It is important to note that polarizing filters will reduce the amount of light available to your camera usually by two f-stops which makes the polarizing filter most commonly used as an outdoor filter.
The neutral density filter simply reduces the amount of light passing through it, darkening the scene. This is more important for a digital photographer than one might think. Digital camera sensors are very sensitive to bright light and tend to record outdoor scenes with far more contrast than traditional film. When a bright scene is blown-out (bright areas are white) there is said to be “clipping.” This means the light information in that part of the scene has been lost because all that has been recorded is white light. A neutral density filter can save this information without forcing the photographer to stop the camera down to an undesired aperture. A neutral density filter can allow a photographer to use a lens at a wider aperture to produce the desired bokeh in bright sun light when otherwise not possible.
There two important things to look for when choosing a filter, coating and thickness. Due to the reflective nature of digital camera sensors a filter with no coating or minimal coating can cause ghosting on your images due to light being bounced back and forth between the sensor and the back-side of the filter. This is usually only a concern when facing a bright source of light, but for many photographers it can be enough of a concern to purchase multicoated filters which reduces ghosting. The thickness of the filter (or thickness of the filter’s bezel) is a concern for wide-angle lenses because these lenses require the light to bend more at the edges than in the middle of the frame which means the light at the edges of the frame is required to pass through more of any attached filter’s glass. Generally speaking the more glass light is made to travel through, the dimmer it becomes, and thus a thick filter on a wide-angle lens will result in some vignetting. For extremely wide-angle lenses the thickness of the bezel can also make a difference as the light coming in at extreme angles at the edge of the frame can be blocked by a thicker bezel on a filter. Some modern filters such as the Hoya Pro 1 Digital series of filters have been specially designed for digital cameras with thin glass elements, a thin bezel and a specially designed coating that prevents ghosting and flare. However, any professional filter that is multicoated such as those made by B+W will also work just as well with a digital system.
If you still don’t believe that a couple of filters will make a difference, go out and try some and see the difference for yourself and as always, happy shooting!