A Brief Overview on Neutral Density Filters
Have you ever look at a photo of, for example, a waterfall, and noticed how silky smooth the surface of the water is? It is the result of a technique called long exposure. Long exposure is quite simple to do in theory, all you need to do is decrease the amount of light passing through the lens within a given time and prolong the exposure time. In practice, there are many situations where it is impossible to take long exposure shots due to bright natural light.
This is when Neutral Density Filters, or ND Filters, come in handy. A ND filter is essentially a piece of dark glass that is screwed onto the front of the lens to limit the amount of light passing into the lens. Depending on the optical density and the amount of light that can travel through the glass, different filter is assigned a different rank. For example, a ND64 filter allows in only 1/64 of light that would have pass through when no filter is used. This means that the exposure time can be prolonged 64 times to get the same level of exposure.
ND filters can also be used in non-long exposure shots. If you would like to use wide aperture in broad daylight, you may want to consider getting a ND filter to limit the amount of light coming through so you don’t overexpose your photos. Imagine a scenario where you are taking picture of an object outdoor at noon, it is a sunny day with plenty of sunlight, and you want to capture the subject while blur everything else around it. Because of the amount of lights available, you are probably forced to use smaller aperture so not to over expose the picture, but this does not give you the shallow depth of field you want. By applying a ND filter, you can use a wider aperture to get the depth of field while not overexposing the picture.
A variant of ND filters is the Graduate ND filter. Unlike normal ND filters, a Graduated ND filter has only half of its glass darkened while the other half remains clear. Between the darkened half and clear half is an area where the glass gradually shifts from being darkened into being clear. This type of filter is useful when the scene you want to capture is overexposed in one area and underexposed in another, such as sunrise and sunset.
There are many different brands available on the market, and they offer varying levels of quality and prices. When purchasing a filter, you should always do some research before committing to buy. Aside from the brands, you should always purchase filters that has multiple coating whenever possible to ensure image quality. I would stay away from the cheap filters found online because there are so many counterfeit filters that are either unreliable or do not even work, and I strongly recommend that you buy from reputable sources.
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