Although optical filters are often viewed as an afterthought in machine vision applications, their ability to optimize lighting and the entire vision system makes them so valuable that they should be considered from the initial planning stages of most applications. The value of optical filters arises from their ability to block all unwanted ambient lighting and pass only the output of light needed for inspection while increasing contrast and resolution. To select the right filter for a specific application, first define the imaging objective such as improving contrast, reducing glare, color sorting, and removing barcode interference. Determine the optimal light emitting diode wavelength by testing white light with various bandwidth bandpass filters. Once the appropriate light wavelength has been chosen, the corresponding bandpass filter can be used to control the variables. This article will provide more information on optical filter advantages and selection and provide real-world examples of how optical filters have been used to help solve difficult machine vision challenges.