Filter Naming Conventions

Reading Typical Part Numbers

Understanding Chroma filter part numbers allows you to quickly identify key specifications such as center wavelength, bandwidth, filter type, and coating family.

Excitation filter (e.g., ET480/40x) – For this example, the center wavelength is at 480 nm; full bandwidth is 40 nm (±20 nm). In some cases where the bandwidth is not specified, the letter “x” is used to define the filter as an excitation filter. This is generally used for narrow band UV excitation filters (e.g., ET340x).
Dichroic beamsplitter (e.g., T495LPXR) – The cut-on wavelength where transmission is approximately 50% is 495 nm for this dichroic longpass mirror.
Emission filter (e.g., ET535/50m) – The center wavelength is at 535 nm; full bandwidth is 50 nm (±25 nm).

Prefixes and Coating Families

Code	Description
AT	Magnetron-sputtered exciter, emitter, or dichroic, typically 45° AOI; recommended for only basic, visual applications (such as cell culture) (basic performance)
D	Obsolete parts; early-generation bandpass filter (thermal/“soft” coating)
ET	Magnetron-sputtered exciter or emitter, typically normal incidence (0° AOI) for maximum performance
HQ	Obsolete parts; improved soft-coated bandpass filter
T	Magnetron-sputtered dichroic/polychroic, typically 45° AOI
ZET	Magnetron sputtered exciter or emitter specifically designed for laser use
ZT	Magnetron-sputtered dichroic/polychroic designed for laser use, typically 11–45° AOI

Suffixes and Spectral Function Codes

Code	Description
BS	Beamsplitter or dichroic mirror
DC	Shorthand for “dichroic”, typically 45° AOI
LP	Indicates a longpass filter or dichroic mirror which transmits wavelengths longer than the cut-on and blocks or reflects shorter wavelengths respectively
M	Emission filter
PC	Polychroic beamsplitter. Reflects and transmits more than two bands of light, typically 45° AOI
SP	Indicates a shortpass filter or dichroic mirror which transmits wavelengths shorter than the cut-on and blocks or reflects longer wavelengths respectively
X	Excitation filter
XR	Extended reflection, typically 45° AOI
XRU	Extended reflection including the UV, typically 45° AOI

Glass Type Abbreviations

Code	Description
GG	Green Glass. Longpass absorption glass from Schott Glassworks with cut-on wavelengths in the violet and blue-green regions
LCD	Corning Eagle XG
OG	Orange Glass. Longpass absorption glass from Schott Glassworks with cut-on wavelengths in the green, yellow, and orange regions
RG	Red Glass. Longpass absorption glass from Schott Glassworks with cut-on wavelengths in the red and far red regions
UVFS	Ultraviolet grade fused silica

Filter Naming Conventions

Reading Typical Part Numbers

Prefixes and Coating Families

Suffixes and Spectral Function Codes

Glass Type Abbreviations

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