Best Spectrophotometer for Measuring Transmittance Color

Every material absorbs, reflects, or transmits light, which determines the color we see when looking at an object. Transmission refers to the light waves that pass through a translucent or transparent sample, and spectrophotometers provide quantitative measurements of that data. These devices make it possible to evaluate a sample's color scientifically and objectively, which is vital for ensuring color consistency in various applications. Spectrophotometer transmittance measurements enable better quality control and enhanced consumer perception of your products.

What Is Transmittance in a Spectrophotometer?

The definition of transmittance is the measured light that passes through a sample, meaning the light that is not absorbed or reflected. Three primary transmittance measurements include:

• Diffuse transmittance (Td, n): This measurement is the ratio of the flux transmitted by a specimen to the incident flux, with the transmitted flux being measured at all forward angles except the regular transmission angle. When light is diffusely transmitted, its direction changes as it passes through the material, causing scattering.
• Regular transmittance (tr, n): This measurement is the ratio of undiffused transmitted flux to incident flux. In other words, it is straight-through light.
• Total transmittance (tt, n): This measurement is the ratio of the flux transmitted at all forward angles to the incident flux. Total transmittance is the sum of regular transmittance and diffuse transmission.

These values are essential to maintaining quality in products like beverages and edible oils. It's best to measure color with a spectrophotometer to capture more accurate information, as these devices provide exact quantitative data regarding the amount of light that passes through a sample. 

The transmittance formula is:

T = PT/P0

The values in this formula represent:

• T: Transmittance
• PT: The source's radiation power as it exits the sample
• P0: The source's radiation power as it enters the sample

The resulting calculation is a ratio, comparing the light before it enters the sample to the light after it passes through it. A value closer to 1 means most light passes through, while lower values mean that less light passes through. 

What Is Percent Transmittance in a Spectrophotometer?

Percent transmittance displays the light that passes through the sample as a percentage rather than the ratio created by the above formula. You can get the value by multiplying the ratio by 100. 

A sample with 100% transmittance is transparent, allowing all light to pass through. Lower numbers indicate more translucence than transparency. At least 30% of the light must pass through the material for effective transmittance measurements.

The transmission percentage is also helpful for absorbance calculations. A commonly used absorbance formula is:

A = 2-log10(%T)

This formula determines the amount of light absorbed using the percentage of light that passes through the sample. 

How Does a Spectrophotometer Measure Transmittance?

A spectrophotometer measures the transmittance value by shining a light through a material into a detector. The detector measures the light that passes through and compares it to the original incident light. This comparison provides a ratio you multiply by 100 to get the percentage transmittance.

Here's the process used to set up a spectrophotometer to measure transmittance.

1. Select Mode

In the spectrophotometer controls, you will select the correct measurement mode. Choose TTRAN if your sample is slightly hazy due to light scattering. Conversely, use RTRAN for clear samples without turbidity.

2. Standardize the Spectrophotometer

Before analyzing your sample, standardize the spectrophotometer using tiles supplied by the manufacturer.

If you are measuring a liquid, you will place a blank solution in a transmittance cell during the standardization process. When analyzing water-based products, you can use distilled water as the blank solution.

Equipment like HunterLab UltraScan® Pro and UltraScan VIS can be easily standardized using the light trap and NIST-traceable white tile we provide, while our Vista spectrophotometer offers one-touch standardization.

3. Read Samples

Once you set the top and bottom of the scale using standardized tiles, you can measure the transmittance value for your sample.

Measuring is straightforward with our Vista model. Prepare the transmittance cell with your solution and place it into the compartment. Close the cover and press the green measurment icon to start the process. The resulting L*a*b* values will display onscreen in seconds.

The Importance of Transmittance in Spectrophotometers

Transmittance values provide quantitative data that helps determine the purity and quality of particular materials, from edible oils to pharmaceutical products. This data offers benefits like the following.

Verifying Clarity

When producing goods like edible oils, turbidity in the sample can impact color as particulates scatter light. Particulates can also influence grading and refinement. Pairing transmittance measurements with turbidity quantification enables manufacturers to verify clarity with certainty.

Characterizing Transparency

While a visual assessment gives a general idea of transparency, a transmittance value gives you a particular number for a more accurate comparison to a standard. 

Maintaining Quality Control

Consistency matters to uphold quality and reduce waste, saving your business time and money. Differences in transmittance values can signal a need to adapt production processes to reach these goals. Spectrophotometers quickly identify where shifts arise, enabling manufacturers to make faster adjustments.

Enhancing Consumer Perception

Consumers have visual expectations for the products they buy. If your offerings don't meet those perceptions, customers may turn to a competing product instead.

Analyzing Concentrations

The transmission value gives you a general idea of the concentration of dyes or pigments within a material. This information helps when formulating products, equipping you to achieve more color consistency across batches, facilities, and production lines.

Improving Safety

Transmittance values indicate changes in products, which may help identify spoilage in products such as edible oils and fruit juices. The data allows producers to determine shelf life and the factors that shorten or lengthen it.

Measure Transmittance and Turbidity With HunterLab

Determine the purity of raw materials with the Vista spectrophotometer from HunterLab. This device captures visible range transmission and turbidity data for liquids in a single measurement, enabling you to maintain consistent color and spectral data and enhance quality processes. It can also help you detect contamination in raw components early so you can make any necessary changes. 

Vista is a valuable tool for measuring transmittance in various materials, including edible oils like:

• Vegetable oil
• Safflower oil
• Olive oil
• Palm oil
• Coconut oil

It’s also capable of quantifying color and spectral data in transparent to translucent solids, such as plastic preforms and films.

Vista can measure TTRAN or RTRAN in just 2.5 seconds, keeping your production processes moving. A small footprint enables you to save benchtop space, and a spill-resistant sample compartment protects electronic components from damage when measuring liquids. This spectrophotometer is easy to use, with a 7-inch touchscreen display and a menu-driven interface for operation with minimal training.

Additionally, Vista simultaneously measures color and turbidity in 5 seconds, bringing further value to production.

For added versatility, consider the UltraScan Pro or UltraScan VIS, which measure both transmittance and reflectance.

UltraScan Pro offers TTRAN and RTRAN measurements and captures data across 350 nanometers to 1050 nanometers — the full CIE visible range, plus near infrared and some UV wavelengths. Additionally, this spectrophotometer contains large, medium, and small viewing areas for compatibility with different sample sizes. These features make this spectrophotometer model ideal for ophthalmic lenses and coated glass.

UltraScan VIS also measures TTRAN and RTRAN and quantifies color wavelengths between 360 and 780 nanometers, including some readings within the UV spectral region. Plus, it offers both small and large viewing areas for sample flexibility. Its versatility is ideal in industries like biopharma, plastics manufacturing, and food and beverage production.

Get the Color Measurement Solution You Need

HunterLab is a reliable source of color measurement solutions with over 70 years of experience in the industry. We offer high-quality, easy-to-use products like the Vista, UltraScan Pro, and UltraScan VIS spectrophotometers, perfect for capturing transmittance and turbidity measurements. Get a quote for this solution online today.