Optical Density (OD) is a convenient way to describe the blocking ability of an optical filter. Higher OD values indicate a higher level of blocking. For more information, please refer to our technical note Working with Optical Density.
OD = – log10(T)
Optical Density Noise Floor:
Through careful optimization of our measurement equipment and methods, Semrock is able to provide some of the best wide bandwidth Optical Density (OD) measurements possible. Below are typical OD noise floor limitations for most of the measurement data shown on this website.
* For wavelengths between 320 and 1120 nm, transmission values near or below 3e-7 (Optical Density 6.5) are measurement noise limited.
* For wavelengths < 320 nm and between 1120 - 1500 nm, transmission values near or below 3e-6 (Optical Density 5.5) are measurement noise limited.
* For wavelengths > 1500 nm, transmission values near or below 1e-5 (Optical Density 5.0) are measurement noise limited.
Also, for some filters and/or some blocking wavelength ranges, measurements with a noise floor of only about OD 4 are shown.