Selection within a documented range
Neutral density filter selection is simpler than fluorescence selection, because the documented evidence is a range rather than a list of examples. The documented wavelength range is 200 to 1000 nm, and the documented ND value range is ND 0.1 to 4. Sizes are customized according to customer needs. Selection therefore has three steps: choose an ND value within the documented range, check that your working wavelength range falls within 200 to 1000 nm, and state the size you need. If any step falls outside the documented range, state that requirement in the inquiry and ask for confirmation rather than assuming coverage.
Choosing an ND value
An ND value describes how strongly light is attenuated. A higher ND value means stronger attenuation. The documented range runs from ND 0.1 to 4, which covers light reduction from modest to strong. The right value depends on how much light your system must lose: a measuring instrument bringing a strong signal into its working range, a laser path needing controlled attenuation, a camera or imaging system managing bright light, a security monitoring system handling bright scenes, and an optical communication path balancing signal levels all start from different light levels and therefore need different ND values. State the light level problem you are solving, not just the ND value you first guess, so that the value can be checked against the application.
Checking the wavelength range
Check your working wavelength range against 200 to 1000 nm. That range covers ultraviolet through visible into near-infrared work, which matches the documented application fields: ultraviolet measuring instruments, lasers, optical digital cameras, video cameras, security monitoring, optical instrument equipment, optical communication attenuation, optical imaging systems, smoke meters, optical measuring instruments, near-infrared spectrometers, and biochemical analysis. If your application works outside that range, say so in the inquiry. If it works inside that range, say which part of the range matters most, because attenuation behaviour across a range is more informative than a single wavelength point.
Size and ordering
Size is the third selection step, and it is a custom step: sizes are customized according to customer needs, so there is no fixed size table to choose from. State the size you need, together with the shape and mounting approach if they matter. Then state the quantity basis and the delivery basis you need confirmed. For the product evidence, see neutral density filters. For the application fields in more detail, see the neutral density filter applications note. For buying, see the ND filter manufacturer page.