Filters 101

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Filters are basically tools to modify the quality of light hitting your sensor. They used to play a more integral role in photography before digital cameras came along. Nowadays, a lot of people discount the importance of photographic filters thinking that they can replicate any effect they want during post-processing. This is not entirely true. There are some filters that can never be replicated on the computer no matter how good you are with Photoshop.

There are literally dozens of filter types available in the market today that can cause a first time buyer some confusion.This article will discuss some of the most basic and important types to help get you started.

FILTER MOUNTING

Filter mounting refers to how the filter attaches to your lens. The two most common filter mountings are threaded and the square filter system. Threaded filters are circular in shape and just screw on directly to the lens. Square filters require a filter holder to attach the filter to the lens.

Some types of filters, such as the protect filter, are available only as threaded filters while some like gradient filters are better used in their square form. These will be discussed further in the article.

FILTER SIZE

To find the filter size that’s needed for your particular lens, you need to look at the front of the lens with all the marking on it and look for the symbol in the photo below.


CC Photo by William Hook

Different lenses have different filter sizes. This means that one size will definitely not fit all. To avoid having to buy the same filter for each type of lens you own, we suggest buying converters or step-up rings. Step-up rings allow you to attach a threaded filter that has a bigger size than that of your lens. The photo below is an example of a B+W step-up ring that attaches to a lens with a filter thread size of 72mm to a filter that is 77mm.

FILTER TYPES

• UV / PROTECT FILTERS

Protect filters do just that, protect your lens. It is basically just a clear piece of glass that screws on the front of your lens to protect it from dirt and scratches.

UV filters block ultra-violet light in a scene which can cause your image to lose some sharpness. Does it work? I have no idea. We’ve been taking photos for a very long time before we attach a UV filter to our lens’ and I have yet to notice a difference in image quality. We mainly use UV filters to protect the frontal element of our lens much like what a protect filter will do.

• COLORED FILTERS

Colored filters are classified by Wratten numbers with each number corresponding to a specific hue or color. The system was named after the Frederick Wratten who established a company in the early 1900′s specializing in filters. You can see a listing of Wratten numbers with their specific colors here. These types of filters add color to the scene. The most commonly used colored filters for photography are warming and cooling filters. You can try the Cokin 81 series filters to warm up a scene or the 82 series filters to cool it down.

The practically of colored filters have gone down with digital cameras. You can get the same effect by playing around with your white balance setting. Check your camera’s manual on how you can enter a specific color temperature for white balance so you won’t be limited by the usual presets of daylight, shade, etc.

• CLOSE-UP FILTERS

Close-up filters are the way to go if you don’t want to spend on a dedicated macro lens. These filters enhance your lens’ magnification power by lowering the minimum focusing distance so you can move much closer to your subject. The filter’s strength is measured in dioptres with the weakest being +1 and the strongest at +10. Your lens’ focal length will also determine the magnification factor. For example, an object will appear larger if you use a 100mm lens with a +3 dioptre as opposed to using a 50mm lens with the same filter. The photo below is a close-up filter set from Hoya.


Of course the image quality will never be equal to that of a macro lens but close-up filters are still a lot better than cropping during post processing.

For more on filters, proceed to Filters 101, Part 2.

RELATED READING: How to Protect Your Lens

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