Camera filters act like tinted glasses for a camera. By restricting or altering the light which reaches the camera lens, they can improve the quality of an image. Some filters are used to resolve technical difficulties, such as unwanted glare and reflections. Others may simply be used to create fun effects. Here is a rundown of the key filter types along with information about how they are used and what to look for when buying them.
Polarising Filters are used to filter out white light. This makes them one of the most crucial accessories for photographers, since it is extremely difficult to produce quality images of any sort of reflective surface without them. An extra benefit of polarising filters is that they make for much richer colours.
There are some important points to note when using polarising filters. Firstly, the fact that they reduce the light available to the camera's sensor means that either a slower shutter speed or a larger aperture (F stop) must be used to compensate. Since the aperture controls the depth of field, which is important from the point of view of composition, most photographers choose to use a slower shutter speed. Unfortunately slower shutter speeds increase the impact of camera-shake, which means that shooting handheld is challenging at the very least. The best way to deal with this issue is to use a tripod. For those who prefer to travel light, there are smaller, portable tripods available, such as Gorillapods. It is also often possible to improvise with some sort of flat surface, although this is far from ideal.
Another issue with polarising filters is that their effect can be uneven, particularly when using wide-angle lenses. This is most common when taking photographs of subjects lit by overhead lighting (such as the sun at its highest point). It may be possible to work around this difficulty by rotating the filter so that its strongest impact is in a corner or upper edge. Provided the main interest is elsewhere, the viewer will probably accept this as a natural change in the sky. Polarising filters must be kept absolutely, scrupulously clean in order to function effective. Dirty filters are worse than useless.
When buying polarising filters, look for circular filters rather than linear ones. The difference is that circular filters are designed so that autofocus and metering systems will still work through them. They are more expensive but significantly more convenient.
Neutral Density Filters
Neutral Density (ND) filters are essentially sunglasses for camera lenses. When shooting in places where the human eye needs protection from the sun, the chances are that the camera lens will appreciate it too. They are also useful for smoothing out differences between strongly-lit areas and darkly-shaded ones. This can help when setting the exposure.
Unlike polarising filters (which only block one type of light), ND filters darken the whole image. They have no impact on how the camera lens perceives colour, however they can trick the photographer's eye through the viewfinder. For this reason, many photographers compose the image before putting on the ND filter.
There are two types of ND filter: single-level and graduated. Single-level ND filters are far cheaper than graduated filters. It should be remembered that because single-level only offer one level of filtering, photographers generally carry around a selection of them to ensure that the right level of filtering can be achieved. Graduated ND filters can be fine-tuned on the camera, meaning that photographers only have to carry one of them.
Although the camera lens functions in much the same way as the human eye, there can be very significant differences between how humans perceive images and how the camera lens does. The reason for this is that the human brain is far more sophisticated than any camera software and it edits images so that they always look the way they ought to look. One of the ways it does this is to compensate for the effect of different types of light so that familiar objects always look their usual colour. The camera lens, on the other hand, captures what is actually there, meaning that if the ambient light affects the colour of a subject, it will show in the final image.
The three most useful colour filters are blue, orange, and clear. Blue filters cool down an image. They are particularly useful for shooting in cities at night as the many artificial lights found in most cities tend to give off an orange colour cast, which is counterbalanced by blue. Orange filters are used to warm up an image. In addition to stopping images taken in blue/grey lighting from looking too cold, they are also very useful for adding impact to images which are already technically correct. For example, classic shots of autumn foliage can be made even more dramatic by using an orange filter. Clear filters are used to protect the lens (and other filters), particularly around water. Essentially, it's far cheaper to damage a clear filter than to damage a good camera lens.
A collection of the aforementioned filters is an excellent starting point for any amateur photographer. There are many other filters available for specific purposes, such as UV filters, which act like sun-protection cream for camera lenses; fluorescent filters, which counterbalance the effects of fluorescent light; and infra-red filters, which are mainly for scientific photography. These can be bought as when and if necessary.
Understanding Filter Mounts
Most filters are screw-on, which means that they screw directly on to the camera lens. Because of this, they need to be bought in the right size to fit the lens with which they will be used. Common filter sizes include 52 mm, 58 mm, 62 mm, 67 mm, 72 mm, and 77 mm. Some very wide telephoto lenses (300 mm or bigger) may have drop-in compartments for filters. Filter kits allow photographers to use one filter for lenses of different sizes. Essentially they involve fitting a special filter holder to the front of the lens. Some of these kits are designed to fit one specific make (or even model) of camera, others can be used across different types of camera. This should be marked clearly in the listing and in case of doubt; the seller should be able to provide the information.
Filter ring adaptors allow filters to be used on lenses for which they are not officially compatible. Step-up rings allow photographers to use filters for larger lenses and step-down filters adapt filters designed for smaller lenses.
Finding Camera Filters on eBay
To find camera filters on eBay, start with the category Electronics and choose Cameras & Photography. Click on Lenses & Filters. The Categories listed under this heading include Filters, Filter Rings & Holders and Other Lenses & Filters. Clicking on Filters leads to a choice of options, including Type, Brand, Condition, Price, Special Effect Type, Shape, Mount Fitting, Colour, To Fit Lens Front (mm) and Seller. The category Filter Rings & Holders is a useful place to look for adaptors to enable lenses to be used on different types of lenses. The category Other Lenses & Filters can be a fun category to browse for more unusual accessories.
Camera filters are affordable and useful accessories for the keen amateur photographer. They can make the difference between an acceptable image and an excellent one. eBay is a great place to look for a wide range of camera filters at competitive prices. All buyers can rest assured that they are protected by eBay rules which require sellers to disclose all relevant information about the camera filters they are selling. This includes postage costs, which should be very low for camera filters unless urgent delivery is required. Where problems do arise, many can be resolved by communication between buyer and seller; however if this is not the case, eBay is there to assist.