Transmittance is the light which passes through the sample. The originating light comes from the instrument's light source, some of which is absorbed and reflected. The transmittance value, often represented by a precent, is read by the instrument's detector.
Transmittance follows the Beer-Lambert law, like absorbance.
For liquids, Absorbance = - log10 (Transmittance).
Light in - Reflected Light - Transmitted Light = Absorbance
Expensive neutral density filter were historically the only way to validate an instrument’s transmittance readings. The In-Spec® product line can provide inexpensive, ready-to-use pourable bottles to help your validation needs.
Our kit #8446 is recommended by BMG Labtech for use with the Nephelostar instrument. This kit includes 20%, 40%, 60%, 80%, and 100%T standards at 635nm. These standards are also available individually. Custom transmittance standards can be made up upon request at any wavelength.
The In-Spec® transmittance standards are NIST traceable and completely non-toxic.