Basic Photography Filters for DSLR Camera

The facility of clicking the image in digital format provides us lot of flexibility. Multiple accessories, which are used in film regime, can be managed using any good photo editing software. But there are still some controls, which can be applied only at the optical level instead of digital level. This means, some accessories are still indispensible and most prominent among those are filters.

Filters are fine glass with different properties, position between optical path of light and the lens. Each lens has its outer diameter in "mm", we need to use the same size of filter. This is standardized up to some level, i.e., we have some specific diameters of the lenses such us 50mm, 52mm,67mm, 58mm, 77mm, 95mm, etc. Apart from providing extra control of incoming light, filters also provide:

• Protection to the glass surface of the lens from accidental damage, and frequent cleaning.
• The cost of filter is generally small fraction of the cost of the lens, so a plain or UV filter is must on every lens.
• Weather sealing for the lens

The two main drawbacks of the filter are that, it being an extra glass element in front of lens can introduce defects at optical level and slow down the AF speed of the lens. However, this effect is negligible and un-noticeable. One can always choose a better quality of filter to keep this affect to minimum. Highly professional photographers may only need to worry about it.

Here are basics of most important filter.

• Plain Filter: This is just a plain glass for the protection of lens. This does not change any property of the light.
• Ultra Violet (UV) filter: It absorbs the ultraviolet rays which often makes outdoor photographs hazy and indistinct. It is primarily helpful in landscape shots where we have blue sky. It also serves as a permanent lens protector, so a must for every lens.
• Circular Polarizing (CP) filter: This filter works on the special property of reflected light. Whenever light reflects from shining surface (such as glass, water, etc), they turn their orientation by certain degrees. This is called polarization. Circular Polarizing Filter helps in managing this reflection. It allows you to remove unwanted reflections from non-metallic surfaces such as water, glass etc. They also enable colors to become more saturated and appear clearer with better contrast. This effect is often used to increase the contrast and saturation in blue skies and white clouds. You can just rotate the filter to get the desired effect. This filter must be part of every nature and landscape photographer's kit.
• Neutral Density (ND) Filter: The ND filters reduce the amount of light entering the lens so wider apertures can be selected without reducing the shutter speed on a bright day light. This is perfect for portraiture to reduce depth of field. The subject appears crisp and clear while the background becomes a soft blur. It is also widely used for photographs of waterfalls and other nature scenes to emphasize movement, because we can use slower shutter speeds on bright day light. Without this filter, you will need to wait for the sun set to get the similar effect.
  These are generally available with ratings ND2, ND4, ND8, ND16 and so on. Each "n" multiple of 2 here represent the decrease in light by "n" f-stops. For e.g., ND8 means the light will be decreased by 3 f-stops (2^3 = 8).
• Graduated Neutral Density (GND) Filter: These filters have the same principle as the regular ND filters but with one important distinction, they do not have the ND effect on the whole glass. The ND effect is gradual and is perfect if you want to have the sky darkened but not the foreground (which is helpful when we have bright sky and dull foreground). The top half decreases the amount of light being let in (usually by 1, 2 or 3 'stops') while the bottom half lets the darker part of your scene to be exposed normally. These filters have their limits, such as the gradual transition is a straight line, which might not always be the case with nature. They are also rather expensive. Most of these filters are rectangular and uses a special holder to place them in.
• Soft focus filter: It creates a picture with a clear focus and a soft gradation. This effect is especially evident on an object with a point light source. This filter has randomly arranging minute lens shaped like drops of water on the surface of an acrylic board scattering the light and resulting in a soft focus. This is very helpful in giving special effects to portrait shots. However, this affect can be achieved at post-editing level as well.
• Macro Filter: These filters are actually a type of lens, which reduces the minimum focusing distance of the lens. This helps in taking shots from close range giving Macro effect.
• Color Filters: Color filters are available in different colors such as red, green, blue and with different intensities. These help in color correction at optical level. However, we can manage without this filter also as the color correction can be done at post-editing level as well.

To know, learn and practice more about filter, choose from different programs of Indian Institute of Photography.