A few years ago, before smartphones became a serious competitor to traditional cameras and instant filters came into existence, photographers used an array of optical filters to transform their images. Filters were in existence before smartphones and for that matter even before digital cameras came into existence.
Back then photographers had very little opportunity to retouch their images during post-processing. That had to rely on their skills and the tools that they could use during the process of image making to make the image as close to what they wanted right in the camera. This is what necessitated the use of optical filters.
These days, unfortunately, not many photographers use filters, at least not for the optical reasons. They rely more on post-processing tools such as Lightroom and Photoshop to transform their images. But purists, photographers who still believe in the age-old tradition of relying on optical tools, prefer to use filters and get the image as close to as they want to, right in the camera. This also gives them the critical advantage of time saving.
There are many different types of photographic filters out there. Some are meant only for a very specific result. Others, like the Neutral Density filters, are more generalist in their applicability. Before you go about looking for a filter you need to know what exactly it can do to your photography, apart from a host of other compatibility parameters.
Probably one of the most quintessential of all photography tools, the circular polarizer is an optical lens filter that 'polarizes' light. What does it do in layman terms? When light passes through various levels of reflecting elements in the atmosphere the image gets unsaturated. Plus, when you shoot water bodies like seas, lakes or streams, they are highly reflective surfaces making life difficult for the photographer to get a proper exposure.
Polarizers take this reflection off the equation. They do this by preventing light coming in at a certain orientation and only allowing light coming from a particular orientation to pass through. Therefore, any image that has been shot with a polarizer will appear saturated. Colors will pop and reflections reduced. A polarized image of a water body can allow you to see through water and glass Windows.
The effect of a circular polarizer works the best when there is bright sunshine. The effect can be controlled by dialing the front element of the polarizer.
So, does the Cir-Polarizer work in every situation?
No. The first thing that you should know is that this will only work on bright conditions, especially on sunny days. Don’t bother bringing out your Cir-Polarizer on days when it is overcast. The simple reason being if there are no reflections what will the polarizer cut? For example, when shooting a waterfall or brook deep inside a wooded area, you might be tempted to use a polarizer to saturate the colors. But if it is a wooden area with very dim lighting, it is likely not to do any change, in fact you might prefer not to use the polarizer because it is going to cut down light.
Downside to Using Cir-Polarizer
There is one downside to using polarizers. Polarizers will drop about 2-3 stops of light when they are used. So, your images will be under-exposed if you apply the polarizer after you have metered for the scene. You will need to re-meter after the polarizer is mounted in front of the lens and after the effect is dialed in.
Buying a Cir-Polarizer
When buying a polarizer check out whether it is compatible with your camera and lens. Cir-polarizers are the ones that you need to buy if you are using an auto-focusing camera. There is yet another type known as Linear Polarizer. For auto-focusing lenses on your digital cameras, you should opt for the circular polarizer only. If you have manual focusing legacy lenses, then linear polarizers will be ok for you. Having said that, Cir-Polarizers can be used on both contemporary and manual focusing older lenses without any problems.
The UV filters are more widely used than any of the other filters that we have discussed on this list. There are two reasons for that. UV filters are great for cutting through atmospheric haze as well as for protection of the front element of the lens. As a matter of fact more photographers prefer UV filters for the second reason than the first one.
Light from our sun passes through the atmosphere and then touches everything on God's earth. But our atmosphere is filled with all sorts of stuff that disperses and reflects that light. When we photograph something, light gets reflected off the dust particles suspended in the atmosphere, water vapor and everything else. This dispersion creates a 'haze' like effect in our images. You may have seen this haze in your landscape photos.
A good quality UV filter would cut down on this haze and strong UV light. Back in the days of film, UV filters were extremely important because film was (is) very sensitive to UV light. With digital sensors, that problem has been overcome. But the second reason still remains valid and it is something that still drives photographers into buying a UV filter. The simple logic is that you can afford to break a 50 dollar filter but can in no way afford to break a 1000 dollar sharp lens. You would rather let the UV filter take the brunt of all the abuse.
When shopping for an UV filter, ensure that you do not compromise on the quality. Even if you are going to use this filter for the purpose of protection only, you cannot disregard the fact that it will sit in front of the lens and will affect your image quality. There is nothing more depressing than to see a cheap filter sitting in front of an expensive lens.
Neutral Density Filters
If I were you, I’d never ever leave home without a 3-stop ND filter. An ND filter is the functional equivalent of a sunglass for your camera. It cuts light. That's what it does. But beyond this simple three word definition, the utility of a ND filter transgresses to areas you may not even imagined.
The primary use of a ND filter seems to be to slow down the shutter. As the ND filter cuts light, you have the option to use a slower than usual shutter speed. Every ND filter will come with an accompanying marking that will state its light stopping power. 0.3, 0.6, 0.9, 1.2 and so on are the more popular. But there are also markings like ND2, ND4, ND8 and ND16. They both mean the same thing though.
0.3 means one stop, 0.6 means two stops and so on. Here stop refers to halving of the amount of light that enters the camera. So a 0.3 ND filter will reduce the amount of light entering the camera by half. A 0.6 ND filter will reduce the amount of light by half of what the 0.3 ND filter allows (therefore allowing in only a quarter of the light without any ND filter). The same way, ND2 means one stop, ND4 means two stops and so on.
You might be wondering why you need to stop light from entering the camera, as the whole purpose of photography is to capture a bright, well exposed image. The thing is, stopping the amount of light that enters the camera forces you to use a slow shutter speed. That is in effect to compensate for the smaller quantity of light. This in effect opens up a completely new avenue for shooting images.
Things like waterfalls, streams, the clouds rolling in, even landscapes and architecture can be creatively shot with a slow shutter speed assisted by a ND filter (See also: '5 Long Exposure Tips for Landscape Photography'). Architecture specially is a great genre to try this out. You could use a 10 stop ND filer and use a really long shutter speed, to virtually wipe out every moving element in the frame.
ND filters are the most versatile of all filters. They also come in various types, shapes and light stopping power. Finding the right filter requires you to do some thinking as to what exactly you need to shoot and then opt for the right filter that will help you achieve that. It can quickly get confusing if you are not properly guided.
You already know what the markings on the filter say. The next thing that you need to do is make up your mind whether you need square shaped filters or round shaped. Round filters need to be matched to the filter thread specification of your lens. The same as UV filters as well as the Cir-Polarizers that you just finished reading above.
If you use multiple lenses for your outdoor photography, buying round filters mean you will have to buy one for each of the lenses. With ND filters and their varying light stopping powers, you may end up having to buy several filters per lens. That is extremely expensive. The solution is to buy square filters.
Square filters will allow you to use the same filter across all your lenses. All you need is a filter holder adapter ring that will hold the filter holder in place (you need one adapter ring for each lens size), one filter holder and of course the filter itself.
Graduated ND filters
ND filters come in various types too. You have solid ND filters which have the same light stopping property across the filter. Then there are graduated ND filters, these are perfect for working in scenes where there is a lot of difference in light across the scene. These filters are solid at one edge of the filter and then gradually turns clear as you move to the opposite edge.
These filters are perfect for landscape images especially when there is a difference in lighting between the foreground which is dark and the background which is super bright (the sky).
Apart from these graduated ones, there are other filters such as reverse graduated, hard edged, soft edged and so on. Hard edged filters are the ones that have an abrupt clear to dark area. In other words there is no 'transition' between the darker edge and the clear edge. These filters are perfect for scenes where the dark area and the bright area are clearly defined.
Soft edged ones are the graduated ones that are the most popular. These filters have a transition area between the clear and the dark side. These filters are perfect when the light across the scene changes gradually.
Reverse graduated has the densest light stopping coating towards the middle of the filter. It then clears out as you move towards the edges. These filters are ideal when the frame is the brightest towards the center.
Color filters / Warming Filters / Cooling Filters
Color filters are basically ones that are used to adjust the color balance of a scene. Let's say that you are shooting on an overcast day but you need a warm golden hour effect for your images. That may sound like a few adjustments in Adobe RAW. But it is possible to get the same effect by using a filter. More specifically a CTO filter. A CTO filter or Color Temperature Orange filter is used to 'warm-up' the image. This is useful specifically for overcast days. The same way if you want to 'cool down' an image you need to use a Color Temperature Blue or CTB filter.
Using these filters require a slightly more technical approach. First you need to get your camera white balance to the precise color temperature of the light that you are shooting in. Setting Auto White Balance would force the camera to try to 'correct' the color cast being imparted by the filter. That would defeat the whole process of using the filter. Using a custom white balance ensures that the camera does not try to arbitrarily use a white balance setting.
Please note that some polarizers and ND filters do come with the color toned varieties as well. These filters do offer some amount of color to the scene, apart from doing their main job, that is polarize or stop light. These filters thus serve dual purposes.