{"id":981,"date":"2026-08-25T10:18:58","date_gmt":"2026-08-25T01:18:58","guid":{"rendered":"https:\/\/iupizeta.mgc.co.jp\/?post_type=column&p=981"},"modified":"2026-08-26T09:30:10","modified_gmt":"2026-08-26T00:30:10","slug":"light-transmittance-haze","status":"publish","type":"column","link":"https:\/\/iupizeta.mgc.co.jp\/en\/column\/light-transmittance-haze\/","title":{"rendered":"Difference between total luminous transmittance and haze \u2014 how to read optical resin transparency"},"content":{"rendered":"\n

Catalogs for transparent materials list two figures side by side: \u201ctotal luminous transmittance\u201d and \u201chaze.\u201d Both are indicators of transparency, but they describe different things. Even at the same transmittance, a different haze value produces a completely different appearance. This article organizes the distinction between the two \u2014 covering standards, measurement, values, and how to interpret them in design.<\/p>\n\n\n\n

\ud83d\udccc Summary in three points<\/p>\n\n\n\n

Total luminous transmittance is the amount of light that passes through. Haze is the proportion of that light which is scattered.<\/p>\n\n\n\n

The two are governed by separate standards: total luminous transmittance by JIS K 7361-1:1997, haze by JIS K 7136:2000.<\/p>\n\n\n\n

Whatever falls short of 100% is due to surface reflection, absorption, and scattering. Values reported without a thickness are not meaningful for comparison.<\/p>\n\n\n\n

What Is Light Transmittance? The Difference Between Total Luminous Transmittance and Haze<\/h2>\n\n\n\n

Light transmittance: a general term for how much light gets through<\/h3>\n\n\n\n

Light transmittance is a general term for the proportion of incident light that passes through. Eyewear and automotive window film use \u201cvisible light transmittance,\u201d while resin property tables use \u201ctotal luminous transmittance.\u201d<\/p>\n\n\n\n

Total luminous transmittance is the total amount of light that passes through<\/h3>\n\n\n\n

Total luminous transmittance is the proportion of incident light, applied perpendicular to a sample, that emerges as transmitted light. It is defined as the sum of parallel transmitted light and diffuse transmitted light (JIS K 7361-1:1997).<\/p>\n\n\n\n

Haze is the degree of cloudiness<\/h3>\n\n\n\n

Haze quantifies the degree to which an image transmitted through a transparent medium appears clouded; it is also called the degree of cloudiness.<\/p>\n\n\n\n

By definition, it is expressed as the percentage obtained by dividing diffuse transmittance by total luminous transmittance. Diffuse transmitted light refers to light that has been scattered forward, deviating 0.044 rad (2.5 degrees) or more from the direction of the incident light (JIS K 7136:2000).<\/p>\n\n\n\n

How the four metrics relate<\/h3>\n\n\n\n

Total luminous transmittance \u2014 the sum of parallel transmitted light and diffuse transmitted light<\/p>\n\n\n\n

Parallel transmittance \u2014 parallel transmitted light only<\/p>\n\n\n\n

Diffuse transmittance \u2014 diffuse transmitted light only<\/p>\n\n\n\n

Haze \u2014 the proportion of diffuse transmittance within total luminous transmittance (%)<\/p>\n\n\n\n

So even at the same total luminous transmittance of 90%, a haze of 0.3% and a haze of 3% look very different. The former produces a clear transmitted image, while the latter produces a clouded one.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Measurement Methods and Standards for Total Luminous Transmittance and Haze<\/h2>\n\n\n\n

The two are measured under separate standards<\/h3>\n\n\n\n

Even when measured on the same instrument, the two metrics rest on different standards.<\/p>\n\n\n\n

Metric<\/th>JIS<\/th>Corresponding ISO<\/th>Scope<\/th><\/tr><\/thead>
Total luminous transmittance<\/td>JIS K 7361-1:1997<\/td>Based on ISO 13468-1:1996<\/td>Transparent and nearly colorless. Thickness of 10 mm or less. Materials containing fluorescent substances are excluded.<\/td><\/tr>
Haze<\/td>JIS K 7136:2000<\/td>Based on ISO 14782:1999<\/td>Transparent and nearly colorless. Haze value of 40% or less.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Source: JIS K 7361-1:1997 \/ JIS K 7136:2000<\/p>\n\n\n\n

JIS K 7105 once covered both metrics comprehensively, but that standard has been abolished, and each metric is now governed independently (Nippon Denshoku Industries). The ISO standards have also been revised; the current versions are ISO 13468-1:2019 and ISO 14782:2021. When identifying a standard, the year must be included as part of the reference.<\/p>\n\n\n\n

Measured with an integrating sphere and a haze meter<\/h3>\n\n\n\n

Capturing scattered light requires placing the sample against a sphere with a white interior (an integrating sphere). Multiple reflections inside the sphere integrate the light before it reaches the detector, so no scattered light is missed (Shimadzu Corporation).<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The instrument used is called a haze meter, and it measures all four metrics at once. Samples should be circular, 50\u201360 mm in diameter, with at least three samples measured (JIS K 7361-1:1997).<\/p>\n\n\n\n

Three cautions when comparing measured values<\/h3>\n\n\n\n

Match the thickness \u2014 absorption and scattering increase with thickness, so values without a stated thickness cannot be compared.<\/p>\n\n\n\n

Match the standard \u2014 values under the abolished JIS K 7105 diverge from those under the current standards.<\/p>\n\n\n\n

Account for differences between instruments \u2014 the current standards correct for changes in integrating-sphere efficiency using a \u201ccompensation aperture\u201d (Nippon Denshoku Industries).<\/p>\n\n\n\n

Total Luminous Transmittance and Haze of Key Materials<\/h2>\n\n\n\n

Key materials at a glance<\/h3>\n\n\n\n

Only official values for which both thickness and the test standard could be confirmed are listed.<\/p>\n\n\n\n

Material (product example)<\/th>Total luminous transmittance<\/th>Haze<\/th>Refractive index (nd)<\/th>Thickness<\/th>Test standard<\/th><\/tr><\/thead>
PMMA<\/td>93%<\/td>0.3%<\/td>1.49<\/td>3 mm<\/td>JIS K7361-1 \/ JIS K7136<\/td><\/tr>
PC film<\/td>90.3%<\/td>\u2212<\/td>1.585<\/td>0.25 mm<\/td>ISO 13468-1<\/td><\/tr>
PC sheet<\/td>90% or higher<\/td>Under 1.0%<\/td>\u2212<\/td>2.0 mm<\/td>ISO 13468-1 \/ ISO 14782<\/td><\/tr>
COP<\/td>92%<\/td>\u2212<\/td>1.535\u20131.536<\/td>Not stated<\/td>Not stated<\/td><\/tr>
PS<\/td>\u2212<\/td>\u2212<\/td>1.590\u20131.600<\/td>\u2212<\/td>\u2212<\/td><\/tr>
Glass (float glass)<\/td>\u2212<\/td>\u2212<\/td>Approx. 1.52<\/td>\u2212<\/td>\u2212<\/td><\/tr>
Special PC (Iupizeta\u00ae EP)<\/td>\u2212<\/td>\u2212<\/td>1.616\u20131.671<\/td>\u2212<\/td>\u2212<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Sources: Mitsubishi Chemical Acrypet; Teijin Panlite optical grades; Zeon Corporation ZEONEX, ZEONOR; Mitsubishi Engineering-Plastics Iupilon, Novarex property data; general properties of sheet glass; Iupizeta\u00ae EP product information<\/a><\/p>\n\n\n\n

Reading the table with care<\/h3>\n\n\n\n

Thickness and test standard are not aligned across materials, so a strict side-by-side comparison does not hold.<\/p>\n\n\n\n

A \u201c\u2212\u201d indicates that a published value could not be confirmed. The test standard for refractive index is JIS K 7142 \/ ISO 489.<\/p>\n\n\n\n

For a comparison by material type, see our article on this subject.<\/a><\/p>\n\n\n\n

Three Reasons Transmittance Never Reaches 100%<\/h2>\n\n\n\n

Surface reflection: some light always bounces back at entry and exit<\/h3>\n\n\n\n

Light partially reflects at any boundary between materials of different refractive index; this is called Fresnel reflection. Even a material free of cloudiness or absorption will not reach 100% transmittance. Glass with a refractive index of about 1.5 reflects roughly 4% at one surface and about 8% across both surfaces (Shimadzu Corporation; general properties of sheet glass).<\/p>\n\n\n\n

In general, the higher a material\u2019s refractive index, the greater its surface reflection. The theoretical upper limit on transmittance without a coating is therefore lower for higher-index materials \u2014 a limit unrelated to any cloudiness in the material.<\/p>\n\n\n\n

This reflection loss can be substantially reduced with an antireflection (AR) coating (Shimadzu Corporation). Optical design should therefore evaluate the transmittance of the coated optical system, not the bare material alone.<\/p>\n\n\n\n

Absorption: specific colors are absorbed by the molecular structure<\/h3>\n\n\n\n

Absorption is the phenomenon in which light of specific wavelengths is absorbed, depending on molecular structure. When the shorter wavelengths (the blue region) are selectively absorbed, the transmitted light takes on a slight yellow tint.<\/p>\n\n\n\n

Scattering: light scatters when it strikes optical inhomogeneities<\/h3>\n\n\n\n

Scattering occurs when light strikes optical inhomogeneities of a different refractive index and changes direction. Causes include foreign matter, bubbles, or crystal grains inside the material, as well as surface irregularities. Cloudiness can appear even without absorption, and haze is the metric that measures this scattered component.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Note also that ISO 14782 includes a caveat: on worn or matte surfaces, haze can be calculated lower than its true value.<\/p>\n\n\n\n

How Transmittance Is Treated in Practical Optical Design<\/h2>\n\n\n\n

Internal transmittance and total luminous transmittance are different quantities<\/h3>\n\n\n\n

Catalog values for optical glass are given as \u201cinternal transmittance,\u201d which excludes surface reflection (HOYA). Total luminous transmittance for resins, by contrast, includes surface reflection. Comparing the two directly and concluding that \u201cglass is more transparent\u201d amounts to comparing figures defined in different ways. Use internal transmittance when comparing a material\u2019s intrinsic properties, and total luminous transmittance when evaluating the light throughput of a part.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Transmittance matters at the level of the optical system, not a single lens<\/h3>\n\n\n\n

A lens assembly is built from multiple elements. Each element has two surfaces, so reflection losses accumulate with the number of surfaces in the system. Reflected light becomes stray light, which can also cause ghosting and flare.<\/p>\n\n\n\n

Haze can degrade with molding and in service conditions<\/h3>\n\n\n\n

Even when the material itself has low haze, it can degrade once molded into a part. Causes include silver streaks from resin decomposition during molding, the condition of the mold and release process, and deformation from insufficient heat resistance.<\/p>\n\n\n\n

For related metrics, see the following articles.<\/p>\n\n\n\n

What thermal decomposition is<\/a> \/ What glass transition temperature (Tg) is<\/a><\/p>\n\n\n\n

Transmittance and haze alone do not determine image quality<\/h3>\n\n\n\n

Transmittance affects brightness, and haze affects loss of contrast. Birefringence is another factor that affects image quality. Birefringence is the phenomenon in which light passing through an anisotropic material splits into two refracted rays depending on polarization direction. Beyond bleeding in the image, it can appear as double images or interference fringes, and it shows up in neither transmittance nor haze. The Abbe number also plays a role in how color bleeds.<\/p>\n\n\n\n

Birefringence and the Abbe number are also covered in the following articles.<\/p>\n\n\n\n

What birefringence is<\/a> \/ What the Abbe number is<\/a><\/p>\n\n\n\n

Iupizeta\u00ae EP: A Specialty Polycarbonate for Optical Applications<\/h2>\n\n\n\n

A special PC engineered for transparency in optical applications<\/h3>\n\n\n\n

Mitsubishi Gas Chemical\u2019s Iupizeta\u00ae EP is an optical material developed for optical applications, composed primarily of special polycarbonate resin. Its features are a high refractive index, low birefringence, and high heat resistance; the corporate website also cites high transparency and high processability. Customization to meet specific requirements is possible from combinations of more than 200 monomers.<\/p>\n\n\n\n

For details on Iupizeta\u00ae EP, see the following.<\/p>\n\n\n\n

Iupizeta\u00ae EP<\/a> \/ MGC product information<\/a><\/p>\n\n\n\n

Features and target applications<\/h3>\n\n\n\n

Against a refractive index of 1.58 for general-purpose PC, Iupizeta\u00ae EP falls in the range of 1.616\u20131.671. The Abbe number is 19.2\u201325.8, and Tg is 140\u2013145\u2103. Target applications include smartphone cameras, AR\/VR devices, in-vehicle cameras, and HUDs.<\/p>\n\n\n\n

Note that measured values for total luminous transmittance and haze are not disclosed.<\/p>\n\n\n\n

For related metrics, see the following pages.<\/p>\n\n\n\n

Latest developments: high refractive index<\/a> \/ Iupizeta\u00ae EP product information<\/a><\/p>\n\n\n\n

Summary<\/h2>\n\n\n\n

Key points for reading the numbers<\/h3>\n\n\n\n

Total luminous transmittance indicates the amount of light; haze indicates the degree of light scattering. Whatever falls short of 100% is divided among surface reflection, absorption, and scattering. Comparing values requires matching thickness and standard. For optical applications, judge by the transmittance of the coated optical system, not the bare material.<\/p>\n\n\n\n

About Iupizeta\u00ae EP<\/h3>\n\n\n\n

Iupizeta\u00ae EP is Mitsubishi Gas Chemical\u2019s special polycarbonate resin for optical applications. Grades are available with refractive index 1.616\u20131.671, Abbe number 19.2\u201325.8, and Tg 140\u2013145\u2103.<\/p>\n\n\n\n

For detailed data, sample provision, or help selecting a grade, please reach out via the inquiry form on the official website.<\/p>\n\n\n\n

Iupizeta EP official website<\/a><\/p>\n\n\n\n

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Some images and text in this article were created with the help of generative AI.<\/p>\n","protected":false},"featured_media":914,"template":"","meta":{"_acf_changed":false,"_locale":"en_US","_original_post":"https:\/\/iupizeta.mgc.co.jp\/?post_type=column&p=907"},"column_tax":[52],"class_list":["post-981","column","type-column","status-publish","has-post-thumbnail","hentry","column_tax-basics","en-US"],"acf":[],"_links":{"self":[{"href":"https:\/\/iupizeta.mgc.co.jp\/wp-json\/wp\/v2\/column\/981","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/iupizeta.mgc.co.jp\/wp-json\/wp\/v2\/column"}],"about":[{"href":"https:\/\/iupizeta.mgc.co.jp\/wp-json\/wp\/v2\/types\/column"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/iupizeta.mgc.co.jp\/wp-json\/wp\/v2\/media\/914"}],"wp:attachment":[{"href":"https:\/\/iupizeta.mgc.co.jp\/wp-json\/wp\/v2\/media?parent=981"}],"wp:term":[{"taxonomy":"column_tax","embeddable":true,"href":"https:\/\/iupizeta.mgc.co.jp\/wp-json\/wp\/v2\/column_tax?post=981"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}