A neutral density (ND) filter is a darkened glass affixed to a lens. This filter between the subject and the imaging tool reduces light wavelengths so that colors are not overexposed. ND filters only affect light, not color reproduction, sharpness, or contrast. We’ll explain in more detail how ND filters work, the various types of ND filters, and filter solutions by Evaporated Coatings.

How Do Neutral Density Filters Work?

Filtering the intensity of the colors of light that reach the imaging sensor allows operators better control over shutter speed and aperture selection. Thus, ND filters allow users to capture clear images in intense lighting conditions, yielding results that cannot be created through post-production editing. 

Types of ND Filters

Fixed ND filters, also called solid ND filters, have a coating equally distributed across the filter frame, producing a predetermined filter density. You can choose how dense you want the fixed ND filter to be depending on your imaging conditions. For instance, using a lighter density 3-stop filter allows you to set the shutter speed three times slower. 

Variable ND filters feature two polarized filters working together, where one blocks a set amount of light while the other rotates so that the user can control the total amount of light let in at any given time.

ND filters come in a wide range of polarization levels, from 2x, 4x, 8x, all the way up to 8192x. Each increase in multiplier corresponds to one f-stop, or one EV of light difference registered by the imaging tool. The polarization levels represent optical density (OD) and translate to different percentages of the original lens opening. For example, 2x means a 50% lens opening and 0.3 OD, 4x means a 25% opening and 0.6 OD, and 8x represents a 12.5% opening and 0.9 OD.

Neutral Density Filters from Evaporated Coatings

ND filters allow you to control how much light filters through your imaging tool. They enable better control over shutter speed and aperture settings, so you can create clearer images without affecting contrast, sharpness, or color.

Evaporated Coatings, Inc. has been a leader in optical coatings for more than 60 years. We have maintained this position by innovating vacuum deposition technology and thin film processes. From design to preparation to coating, ECI brings technical knowledge, competitive pricing, and customized service to every client’s optical solution. Our product line covers a variety of optical coatings and substrates. For more information about our products and capabilities, contact us today.