国产一卡2卡三卡4卡麻豆_了解最新日韩草逼视频_h片在线播放一区_国产激情影视在线_好了av四色综合无码久久_欧美黑白双插OOR720P_日本精品中文字幕在线_秋霞午夜手机影院_亚洲国产一区二区3da毛片_欧美杂交深喉video中文字幕

Understanding Neutral Density Filters

Neutral Density (ND) filters are designed to reduce transmission evenly across a portion of a specific spectrum. ND filters are typically defined by their Optical Density (OD) which describes the amount of energy blocked by the filter. A high optical density value indicates very low transmission, and low optical density indicates high transmission (Equations 1 – 2). ND filters can be stacked to achieve a custom optical density. To calculate the final system OD, simply add the OD of each filter together.

Example 1: What is the transmission if OD 0.3 and OD 1.5 filters are stacked?

Example 2: How can I build a filter with 0.5% Transmission?

ODtotal of 2.3 could be created by stacking OD 0.3 + OD 2.0 or OD 1.0 + OD 1.3.

Types of Neutral Density Filters

There are two types of ND filters: reflective and absorptive. Reflective ND filters consist of thin film optical coatings, typically metallic, that have been applied to a glass substrate. The coating can be optimized for specific wavelength ranges such as UV-VIS or NIR. The thin film coating primarily reflects light back toward the source. Special care should be taken to ensure the reflected light does not interfere with the system setup. Absorptive ND filters utilize a glass substrate to absorb light by a specific percentage.