Over the past year, I decided to include filters in my camera kit. I took them on several trips and even on local outings, determined to take the time to use them properly. I started out with the standard collection of screw-on filters – a polarizer, a variable neutral density filter and a graduated neutral density filter. I quickly discovered the pros and cons of these types of filters and expanded my kit to include a square-format drop-in filter system. This consisted of a lens adapter, filter holder and a variety of 100mm square filters.
It’s been an interesting experience that I thought was worth sharing. Here’s what I’ve learned.
First, why would a photographer use filters? Photography, as we all know, is about capturing light. We also seek to control that light – its quality, colour or intensity. There are really only two ways to do that. We can control the light source itself, which of course works for studio or artificial sources, but not natural light. We can also alter the path of light or block some of the light from reaching the camera sensor. We can alter the path of light by placing reflectors, flags or other modifiers around our scene. We can block some light from reaching the sensor by using filters on the camera lens itself.
Filters are most useful when dealing with natural light. By definition, a filter deflects or absorbs certain characteristics of light while allowing others to pass through, thereby “filtering” it. Light is composed of different wavelengths of energy that combine together to provide whatever ambient light is available in a scene. A filter can darken a scene by simply absorbing some proportion of all ambient light, or it can be selective in excluding certain wavelengths of ambient light and thereby certain colours. You can even get filters for wavelengths of light not visible to the human eye but visible to the camera sensor.
Photographers have used filters since the beginning of photography. In the beginning, there was no real way to “colour” a photograph except through the use of filters (I’ll ignore the fact that the chemicals and coatings themselves did impart a colour cast onto prints). In the early days, colour filters in front of the lens were used to selectively highlight or subdue “colours” in the scene and thereby to creatively enhance the tonal variation of a monochrome print.
Most photographers today do in fact use a filter, even if only to protect the front element of the lens they are using. These protective filters can be clear glass or will filter out ultraviolet light, which in earlier days of film and digital sensors, could be damaging to those media. Today, the need for a UV filter or any protective filter is regularly debated. Cameras are no longer prone to damage from UV wavelengths. In terms of the physical protection offered by having another piece of glass on the lens, some argue that the optical interference of potentially imperfect glass isn’t worth the minor protection against abrasion or damage of the front lens element. Lenses are much more physically robust these days. I’ve also heard that a breaking UV filter can itself do more damage to the lens than leaving the lens exposed. And some of these filters can increase the likelihood of lens flare, that wonderful multi-coloured artefact that often occurs in exactly the wrong place in your capture.
Each time a piece of glass is added to the front of a lens, there is a potential for changing the optical quality of the finished image. The better filter manufacturers understand this and create their filters from optically “perfect” glass. That is the stated reason for why better systems are more expensive. So, as with many other things in photography, filter users should purchase the most expensive system that they can afford.
There are two standard configurations for filters – round and square/rectangular. The first may be attached to the threads of the front element of the lens either directly or via an adapter; the second requires an adapter and housing to hold the filter element(s).
One obvious decision is what size filter(s) to get. My preferred approach is to buy only one set of filters to fit the largest width lenses I own, then buy “step-up rings” to attach those filters to any other lens I use. A step-up ring is a simple metal flange with two sets of threads – one to connect the flange to the lens and one to connect the flange to the filter. Filters can run several hundred dollars – flanges are typically 1/10 that cost.
The adapter for square or rectangular filters can also be attached to a flange, so the same premise works for these systems. But the choice of which size square filter system to invest in will depend on the width of the widest lens to be covered. Most filters are either 100mm or 150mm. If you use a wide range of lenses, you may find it silly to connect a 150mm filter to a 52mm front lens element, so consider which lenses you really need filters for and factor this into your decision on what size filters to buy.
I should point out my negative experience with screw-on filters that were the exact size of the lens opening, particularly for wide-angle lenses. I often found colour artefacts and distortions and odd banding present in my images if I was using a wide-angle lens with a fit-to-size screw-on filter and the aperture wide open. I could minimize or eliminate these artefacts if I stopped down to f/8 or higher, which may or may not be possible in all situations.
Those are the mechanics; what about the usage of these filters? Neutral density filters darken down the scene to permit a wider range of shutter values, especially in bright ambient light. Graduated neutral density filters darken down 1/2 of the scene, permitting a better balance between landscape and sky, water and sky or foreground and background. And circular polarizers manage reflected light to eliminate annoying glare in portions of your scene. By the way, the circular in polarizer doesn’t mean it is necessarily physically round – instead it means that you can adjust the angle of correction for glare by a full 360 degrees (which is a circle).
Some photographers argue that all of these benefits can be achieved in other ways: software can recover under or overexposed images, a simple change in shooting angle can eliminate glare, and bracketing exposure then blending the images can deal with exposure balance across the scene. While true, two of these options occur after the fact, meaning that you have left the scene and can’t shoot it again if needed. Having an on-site way of compensating for some of these issues is worth it to me. And some photogs prefer handling something physical, rather than moving a slider on a computer screen.
That’s been my experience. With more outdoor shooting over the past year, the filters have become a valuable part of my kit. I use them almost everywhere, especially the polarizer. Contrary to just dealing with glare, the polarizer can also act as something of a neutral density filter, darkening down the scene slightly but noticeably when needed.
But the effort to put them on and take them off is frankly troublesome. If you are working at a leisurely pace in a fairly static setting, they work very well. If you are hiking, with a tour group or making random stops in a vehicle, adding and removing them is a pain in the butt. Some manufacturers have taken that to heart and have made magnetic versions, popped on and popped off in a jiffy. Not mine. And keeping them clean and finger-print free is a challenge. Nevertheless, the upside had outweighed the downside – I’m often smiling to myself as I see the scene change in front of my eyes to something much better than reality.
There will always be equipment that claims to make your life easier as a photographer. Some of it does, and some of it, frankly, sits in storage unused (despite best intentions). But I would recommend having two filters in your kit – a polarizer and a 3 stop neutral density filter. It’s a modest investment for what could be a really meaningful payoff.