• 01What is visible spectrophotometer?

    Visible spectrophotometer is an instrument that measures color at distinct visible wavelengths and analyzes further in terms of numerical values, spectrograph and other user desired operations.

  • One will have different perception of color red when said red Ferrari and red apple. This tells all about need of accuracy in distinguishing the colors. Each color with all possible shades has to be uniquely represented in digital or say numerical value. Colorimeters and spectrophotometers are the two types of color measurement instruments that are used to measure the color. Color measurement is an essential part of a production process in every industry where color accuracy and consistency is important to maintain the product’s quality and brand reputation.

    Understanding the factors that distinguish spectrophotometer from colorimeter can help you determine the instrument that suits best to you to optimize your color management workflow.

    Sample is illuminated using colorimeter’s internal light source. Reflected light from sample surface is passed through three filters: Red, Green and Blue (RGB). Hence colorimeter can see only three wavelengths and cannot measure remaining wavelengths and so the color accurately. Figure below is the representative image of color spectra that colorimeter sees. Everywhere other than three color peaks, color measurement remains uncertain.

    Spectrophotometer illuminates sample almost in the same way as the colorimeter does. However the main difference is – the color filters. Instead of three filters to determine RGB values like a colorimeter, spectrophotometers typically have large array of filters to measure wide spectrum of color with far better resolution. Figure below is the illustrative image of color spectra of natural sunlight. A visible spectrophotometer can measure and distinguish true color in number of visible wavelengths from 400nm to 700nm.

  • It is common understanding that higher the resolution of the color instrument, better the color measuring accuracy. As spectrophotometers measure entire spectrum instead of just red, green and blue, they provide far more accurate color data; making them useful for broad range of applications in quality control, research and color formulations.

    Normally colorimeters available in market are typically priced at around 200 USD to 1000 USD; while spectrophotometers are priced at about 10,000 USD or even more.

    We feel that the spectrophotometer is the necessity of every production industry and not just the luxury. Price has to be affordable for all while keeping the technology and quality at top notch. After a long dedicated research, we could engineer so far world’s one of the most economic non-contact color instrument – Sensegood Spectrophotometer, priced at below 250 USD. We chose to work with small profit and controlled supply chain to achieve low prices.

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  • Full-spectrum source produces light throughout the entire visible spectrum. It is a neutral white light that has power distribution in all visible color wavelengths from 400 to 700nm. To achieve true color reflected from the object, balanced white light source must be applied. However the artificial light sources have uneven spectral power distribution which is often compensated by mixing various light sources. Further spectral balancing is achieved by firmware algorithms.

  • Photo: Living room objects in warm and cool white LED lights.

    Photo: Spectral distribution of different indoor light sources.

    Source: Kim, Soyeon & Jahandar, Muhammad & Jeong, Jaehoon & Lim, Dong. (2019). Recent progress in solar cell technology for low-light indoor applications. Current Alternative Energy. 03. https://doi.org/10.2174/1570180816666190112141857

    Not all white light sources are perfectly white. They have different color power distribution in uneven white spectrum, often correlated by color temperature: cool or warm. Object absorbs or reflects colors depending on its own color properties and the color distribution of the applied light source. Objects appear redder under the illumination of warm white LEDs or in light during sunrise. Same way, objects seem bluer under cool white LEDs or in midday sunlight. Hence it becomes very important to carry out color measurement by using standard independent light source.

  • Photo: Graphical representation of color temperature in visible spectrum. Source: Dariusz Kowalczyk, License: Creative commons attribution

    The correlated color temperature (CCT) of a light source is the temperature of an ideal black-body radiator that radiates light of a color comparable to that of the light source. Color temperatures over 5000 K are called "cool colors" (bluish), while lower color temperatures (2700–3000 K) are called "warm colors" (reddish). This color temperature of electromagnetic radiation emitted from an ideal black body is represented in Kelvin.

  • Majority of the LCD screens of phones and computers have a very limited capacity to represent the sRGB space. To get a decent on-screen color an expensive monitor is required with full or extended sRGB coverage. From a practical point of view on-screen colors are pretty good to see color "differences" (2 colors side-by-side) as opposite to "absolute" colors. Even high quality color screens cannot replicate "real life" color. A screen is in any case a light source while "real life" colors come from light reflection of physical objects. Displays in different make devices have light sources with different light distribution and reproduces slightly different colors.

  • Non-contact type instrument has benefit of measuring sample’s color from a distance. Because of this, sensor remains scratch proof enabling long life in retaining calibration. While contact measurement instruments are prone to scratches on its optical assembly and often require factory calibration, maintenance and replacement of parts. Contact measurement instruments are messy and difficult in some applications like liquids, slurries, powders and food materials. Further, non-contact instruments are non-messy, ergonomic and also enable online/in-process measurements. In food processing industries, hygiene is maintained, as non-contact measurement avoids any food contact and bacterial accumulation on sensor measuring surface. Sensegood Spectrophotometer is a non-contact type measurement instrument which provides further flexibility of even selecting desired measurement distance depending on your application.

  • Visual color matching is an art. However, when an individual views a potential color match, because of the process of color vision, the nerve light receptors in the eye begin to fatigue. The result is that the color matches begin to appear closer over time, usually after 15-20 seconds of viewing. Also viewing bright colors just before viewing deep colors can affect color judgment without enough time allowed for visual rest and recovery. There are also other factors like aging of the eye, stress and light source that affect the color match decision. Also scientifically it is proven that every individual has different expressive perception towards color.

    There are advantages of instrumental color measurement. It provides numerical color data, a common color language amongst manufacturers and researchers. It eliminates subjectivity in color assessments, eliminates the variability among different analysts and maximizes accuracy and precision.

  • The CIELAB color space (also known as CIE L*a*b* or sometimes abbreviated as simply "Lab" color space) is a color space defined by the International Commission on Illumination (CIE). It expresses color as three values: L* for the lightness from black (0) to white (100), a* from green (−) to red (+), and b* from blue (−) to yellow (+). CIELAB was designed so that the same amount of numerical change in these values corresponds to roughly the same amount of visually perceived change. Apart from Lab, Light-Chroma-Hue (LCh) can be similarly represented as shown in the figure below.

    Photo: CIELAB and CIELCh color spaces

  • Following is the complete set of equations that are implemented in Sensegood Spectrophotometer.

  • • Women distinguish colors better than men.
    • The color wheel was invented by Sir Isaac Newton.
    • People are more likely to forget something when it’s in black and white. A black and white movie, or photograph is often not as easy to recall as a color image. Scientists believe this may be because color has a stronger appeal to the sense and it makes a more lasting impression on the memory.
    • 1 out of 255 women and 1 out of 12 men have some form of color vision deficiency.
    • Blue was once seen as a low-class color. However, new studies conducted by various global marketing firms show that blue is the most common favourite color worldwide
    • Pink soothes the nerves and is used for anger management. It is often used in mental health care institutions and prisons as well.
    • Red is the first color that a baby sees.
    • Some people have a phobia of color: Chromophobia is a persistent, irrational fear of, or aversion to, colors and is usually a conditioned response.
    • Food color influences perceived taste and flavour.
    • Yellow and red together make you hungry. Fast food chains figured this out years ago and use this color combination over and over in branding, advertising and restaurant decor.
    • Colors can trigger deep childhood memories.

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Case study

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