A Procedure A instrument can only report %Haze or %Total Transmittance and CANNOT report color such as XYZ or CIELAB. The instrument has a single detector (photopic Y - C/2 or A/2) mounted on the sphere. The light source is opposite the sample sphere opening. This design is the opposite of a HunterLab transmittance capable spectrophotometer which has the light source mounted on the sphere and a full range detector and grating opposite the sample sphere opening.
A Procedure B instrument is a transmittance capable spectrophotometer, such as the HunterLab VISTA that also must meet a few extra design criteria, such as number and size of openings in the sphere and size of detection beam relative to size of entrance and exit ports of the sphere. The VISTA is fully compliant with ASTM Procedure B.
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