Haze Meter Measurement Principle: Transmittance, Scattered Light, and Haze
Haze Measurement Principle and Instrument Selection
Haze Measurement Principle | How to Understand Transmittance, Transmission, Scattered Light, and Haze
Haze meters are mainly used to measure haze, light transmittance, and transmission in transparent or translucent materials. Typical quality-control applications include plastic films, glass, transparent sheets, packaging, display materials, optical materials, and liquid samples. Transmittance describes a material's ability to pass light, while haze describes the blurring caused when transmitted light is scattered by the material. These indicators are related but are not the same optical property.
Industrial testing commonly uses integrating-sphere haze meters or photoelectric haze meters. By measuring incident light, total transmitted light, scattered light, and scattering contributed by the instrument, the instrument calculates total transmittance, diffuse transmittance, and haze. The correct method depends on sample type, thickness, transparency, surface condition, test standard, and quality-control workflow.
## How does a haze meter work?
When light strikes a transparent or translucent object, some light is reflected at the surface, some is absorbed, and most passes through as transmitted light. Some transmitted light continues close to its original direction; this is parallel (regular) transmittance. Other light is scattered by the material's internal structure, particles, roughness, or hazy appearance. This scattered light is a key component in determining haze.
Under fixed optical conditions, a haze meter collects total transmitted light and scattered light, then calculates haze. Higher haze generally means a larger proportion of transmitted light has been scattered away from its original direction, so the material looks less clear. Lower haze generally means a clearer, more transparent appearance.
## What do Tt, Tp, Td, and Haze mean?
Tt — total luminous transmittance: the total amount of light transmitted through the sample, used to assess overall light transmission.
Tp — parallel transmittance: light that passes through the sample while remaining close to its original direction. A higher proportion generally corresponds to a clearer material.
Td — diffuse transmittance: transmitted light redirected by the internal or surface characteristics of the material; it is generally related to haze.
Haze — the proportion of diffuse transmitted light in total transmitted light, usually expressed as a percentage.
## How should the haze and transmittance formulas be read?
Total transmittance: Tt = Tp + Td
Haze: Haze = Td / Tt × 100%
In general, higher Tt means better light-transmitting ability. Lower haze usually means a higher proportion of parallel transmission and less scattering, so the material appears clearer. Higher haze means a greater proportion of scattered light and a hazier or blurrier appearance.
However, high haze does not necessarily mean high transmittance, and high transmittance does not necessarily mean low haze. Transmittance and haze are different optical indicators with different definitions, calculations, and quality-control meanings. Evaluate them separately.
## Haze versus light transmittance
Transmittance describes the proportion of light that passes through a material and answers whether enough light can pass through. Haze describes the degree to which transmitted light is scattered and the material appears cloudy. Transmittance is commonly used for transparent sheets, films, glass, packaging, and optical materials. Haze is commonly used for clear films, matte materials, display materials, diffuser sheets, and packaging. Higher transmittance often indicates better light transmission; higher haze usually indicates more scattering and a cloudier appearance. When introducing either test, confirm the illuminant, aperture, sample thickness, method, test standard, scattering angle, sample uniformity, and surface condition.
## Which materials are suitable for haze and transmittance testing?
Transparent films and plastic sheets: PET, PC, PMMA, PVC, protective films, diffuser films, and clear packaging can be checked for haze and transmittance.
Glass and display materials: glass, touch panels, display materials, optical films, and transparent covers can be evaluated for appearance and optical quality.
Packaging and food containers: transparent packaging, bottles, jars, boxes, and other packages with transparency requirements can be tested.
Liquids and translucent samples: confirm the container, thickness, optical path length, and required fixture for liquids, translucent materials, or special transmission samples.
## Is a haze meter the same as a transmission tester?
Haze and transmittance are both optical transmission measurements. Some instruments can measure haze, light transmittance, transmission, and color data using the same light source, sensor, and optical structure. However, the data collected and calculated are different, as are the quality-control questions they answer.
If you only need a quick check of a material's ability to transmit light, evaluate a transmittance test. If you need to determine whether a clear material is hazy, scatters light, or loses clarity, evaluate haze measurement. If the application requires transparency, haze, color, or color-difference data together, consider equipment that measures haze and transmission.
## How to choose a haze meter
Laboratory measurements: For stable laboratory testing, transmittance and haze measurements, color data, and report management, consider a benchtop instrument such as the YH1600 spectrocolorimeter/haze meter/transmission meter or another benchtop haze-meter configuration.
Quick on-site inspection: For incoming inspection, production-line checks, shipment sampling, or measurements at multiple locations, consider a handheld haze meter.
Test-standard differences: If a customer specification cites ASTM D1003, ISO 13468, or a particular compensation method, review the differences between ISO and ASTM haze testing, then confirm the instrument and measurement conditions.
## What to confirm before introducing haze testing
- Sample type: film, sheet, glass, liquid, translucent material, or a special shape.
- Test items: transmittance only, or also haze, transparency, color, yellowness, whiteness, and other data.
- Test standard: whether the customer or internal procedure specifies ASTM D1003, ISO 13468, or another method.
- Sample condition: thickness, size, flatness, texture, scratches, bubbles, and uniformity.
## Frequently asked questions
### What is the unit of haze?
Haze is usually expressed as a percentage, for example 20%. It represents the proportion of diffuse transmitted light in total transmitted light; it is not a physical unit like length or weight.
### Does high transmittance mean low haze?
Not necessarily. Transmittance is the proportion of light that passes through; haze is the proportion of transmitted light that is scattered. A material can transmit a lot of light yet still look hazy due to substantial scattering, so assess the two values separately.
### Can a haze meter measure transparent films?
Transparent or translucent films can be evaluated for haze and transmittance. Choose the fixture and method based on film size, thickness, flatness, flexibility, and the applicable test standard.
### How do I choose between a haze meter and a transmittance meter?
If you only need the proportion of light passing through, evaluate transmittance measurement. If you need to determine cloudiness, loss of clarity, or scattering, evaluate haze measurement. If both are required, consider an instrument that measures both haze and transmittance.
### What information should I provide when requesting a haze-meter recommendation?
Provide the sample material, size, thickness, transparency, surface condition, whether it is liquid, the required haze or transmittance measurement, any ASTM or ISO standard, and whether the workflow involves fixed laboratory testing or quick on-site inspection.
## Need to confirm whether a haze meter suits your transparent or translucent sample?
Share the sample material, size, thickness, transparency, test items, and required standards. WINSHOP can help assess a haze meter, transmission-measurement instrument, or handheld haze meter. Contact WINSHOP for a selection recommendation.