Having a good set of filters is not essential for taking good photographs, but very important. Filters give you much more flexibility in achieving the effect you want. Although some filters can be replicated in photoshop, the important ones can't be replicated. Let's take a look at some essential types of filters.
Neutral Density (ND) Filters: These filters reduce the amount of light reaching the camera's sensor. It’s like putting sunglasses over your lens. Everything looks dimmer. Unlike colored filters, neutral density filters equally reduce the intensity of all wavelengths.
But you ask, why do people pay thousands of dollars for fast (large aperture) lenses so that the maximum amount of light reaches the camera. Why would anyone want to reduce the amount of light?
While no one would use a ND filter for high speed work, motion blur is sometimes desirable. If you want to use a slow shutter speed to create motion blur, and at the same time want to minimize depth of field by using a wide aperture, then you MUST use a ND filter to achieve this effect. You can only lower the ISO sensitivity so far.
Sometimes the light is so bright outside that even at the camera’s fastest shutter speed, you can’t open up the aperture all the way. This might happen if you were taking a portrait in bright light, and wanted to open up the aperture to create a pleasingly blurred background.
Also, most lenses are sharpest at an intermediate aperture setting, so with a ND filter, you can get the sharpest shots by not using a super-small aperture.
Graduated ND filters are ESSENTIAL for landscape photography. A graduated ND filter is dark in only half of the filter. Landscape photographs are usually made in early morning or dusk. Thus, when photographing a sunrise or sunset, the sky is generally much brighter than the land. So when you take the shot, you have to either make the sky way overexposed, washing out all the detail, or you can expose the sky properly and make the land below horribly underexposed. A graduated ND filter can fix this by making the light from the sky dimmer, allowing you to properly expose the entire frame.
Graduated ND filters come in two different flavors. Either the transition can be sudden or gradual. A sharp transition is good for a sharp, well-defined horizon, while a softer transition is good for less-defined situations.
Sky Filters: This filter reduces blue colors that occur frequently with outdoor photography. This filter gives a good color balance under most outdoor conditions. Many people use this filter as a lens protection filter. Overall, this filter has minimal effects, and can largely be forgotten in deference to other, more important filters.
Ultraviolet Filters: These filters block ultraviolet light from reaching the lens. Some people think that this can reduce the amount of “haze” in a shot. But in modern digital cameras, this just isn’t true. All glass naturally blocks UV light. This is why in scientific instruments, one must use super-expensive Quartz to get UV light to pass through. So why do most people have a UV filter on their lens? The answer is simple – It’s just to protect the lens from scratches or impact (as in the picture). A UV filter is super-cheap compared to a new lens. Some people even call them "lens protection" filters. I have one on all my lenses, just in case the unthinkable were to happen.
Polarizing filters: These filters block light which reflects off an object in one particular orientation. Light from the sun comes in all polarizations, but once this light reflects off something, the light that is reflected is primarily in one polarization or another. With the polarizing filter, you can selectively block certain reflections. This is especially useful for reflections from water, glass, or the sky. These filters are ESSENTIAL for outdoor photography. They deepen the intensity of blue skies. They reduce or eliminate glare. It’s just like polarizing sunglasses for your camera. Circular polarizing filters are used on autofocus cameras, while linear filters are used on manual focus cameras (the circular ones do not interfere with the autofocus mechanism).
Reflections from the sky? The atmosphere is full of water droplets which reflect the sun’s rays. A polarizing filter can reduce these reflections, making the sky appear darker.
But reflections aren’t limited to the sky and water. Even in shots of trees in a forest, reflections of tiny water droplets on leaves can be minimized with a polarizing filter, making the picture look better.
For shots involving the sky, the effect of the polarizer will be most effective at 90 degrees from the sun. So, if the sun is on the horizon and you are facing it, the effect will be most effective straight up, over your left shoulder, and over your right shoulder. The effect is non-existent straight into the sun or directly away from the sun. This difference in effect can be apparent in wide-angle shots where the polarizer makes one area of the sky appear darker then another. Some people find this effect quite annoying, but others think it looks nice.
The polarizing filter has a ring that rotates in the front. You can point the polarizer at the sky and look through the viewfinder while rotating the ring to see the polarizing effect at work. Most polarizers have a mark on the rotating portion (as in the picture). When this mark is pointed towards the sun, the polarizing effect is maximized.
The cost of a polarizing filter (in addition to the price) is that it costs you about a stop of light. So for dimly lit conditions with fast moving action, a polarizing filter probably isn’t a good choice.
Special effects filters: There are lots of these. Some make bright light look like stars. Others add a diffuse glow, which is especially useful for portrait photography. Still others give a foggy look, or add different colors to the scene. Fortunately, Photoshop can easily mimic most of these, so they are useful mainly for film photography. Photoshop even has it's own camera filter menu where you can choose the effect you want. Personally, I think most of the special effects filters look gimicky, and are best avoided.
The Cokin Filter System: A system that holds square glass filters in front of the lens using a special filter holder. The advantages are:
- You can position the filter any way you want (useful for graduated neutral density filters)
- Cokin filters are significantly cheaper than screw-on filters.
- There are well over 100 different Cokin style filters availible.
- You can use them on all your different lenses, unlike screw-on filters, which can't be used on larger lenses, and can only be used on smaller lenses with a step-down attachment.
Cokin filters come in two varieties, "A " and "P". "A" filters are 67 mm wide, while "P" filters are 83 mm wide. Buying everything in system "P" is highly recommended, as this will reduce vignetting (dark edges) on wider lenses, giving you more flexibility with future lens purchases. There exists a very large X-Pro size, but this is only for use with medium and large- format cameras (not you!).
To use a Cokin filter, fist screw on the appropriate adapter ring onto the lens.
Then slide the filter holder onto the adapter ring until it snaps in place.
Make sure that the filter is absoltely clean. No fingerprints!
Then slide the filter into the filter holder. The closest slot is intended for circular filters like polarizers and star filters, while the two central slots are for square filters.
It's that simple!
Sepia Filter: This filter gives a nostalgic effect to an otherwise normal balck and white photograph. This filter is obsolete because this effect can be easily duplicated in photoshop.
If you have a filter that is too big for your lens, you can purchase an adapter ring to make it work. For example, a 25.5mm to 46mm step up ring is used for a camera (or lens) with 25.5mm threads. The adapter will allow a 46mm filter (or other adapter ring) to fit. Adapter rings can be stacked. To use a 49mm filter on a 25.5mm camera lens, first use a 25.5mm to 46mm step up ring and then a 46mm to 49mm step up ring.
Hope you enjoyed this little tutorial.
