July 8, 2014

              Is Color Always Necessary?

              Basler racer
              Our customers often ask whether they need a monochrome or color camera. The bottom line: Color cameras are not always the best choice. Color images are often just easier on the eyes for many observers. Even beyond tasks where color itself is a key inspection criterion, color cameras are not absolutely necessary.  For applications where specific characteristics can be detected via color (such as red spots on an object), color is usually - but not always - required.

              In fact, these characteristics are often also visible in the black and white images produced by a monochrome camera. In cases where color isn't a crucial part of the inspection task, monochrome cameras are often a better choice, since the color filters used by color cameras make them inherently less sensitive than a black and white camera. On many line scan applications, for example, monochrome cameras may in fact be a better choice.

              The benefits of monochrome cameras over color cameras at a glance:

              • Improved sensitivity: Each pixel is struck by either red, green or blue light. No other wavelengths are received. A monochrome pixel can thus receive up to 3 times the volume of light compared with a color pixel. This results in roughly 1.5 times improved sensitivity in a monochrome camera over a color camera.
              • Low noise levels: Another benefit is that monochrome cameras tend to deliver reduced noise in artificial light situations, since artificial light is not normally composed in the same way as daylight and the camera sensors tend to perceive more noise from colored light in those conditions.
              • Higher resolution: For color cameras working with Bayer patterns (dual line scan cameras), any missing color information is interpolated from the neighboring pixels, while monochrome cameras draw their information directly from the original pixels. This allows for a slightly higher resolution in monochrome cameras.
              • No color fringes: The interpolation of colors using neighboring pixels mentioned above can also lead to unattractive color fringes, especially on high-contrast edges, such as where blacks meets whites.
              • Less complicated installation: Color cameras are more difficult to install than monochrome cameras, as the camera must be calibrated to the color temperature of the illumination source. The process involves a comparison of the individual colors against one another.
              • Better dynamic performance: Monochrome cameras are more capable of evaluating or suppressing oversaturated pixels. Color cameras encounter problems when more than one color channel is oversaturated at any given time, and struggle to detect and compensate for this issue. An image of a traffic light provides a good example: If the red pixel is oversaturated and the green is also oversaturated in part or full, then the light will look orange, with potentially grievous consequences for viewer and machine vision system.
              • Higher sensitivity in the Near Infrared (NIR) range: In general, it is fair to say that monochrome cameras are more sensitive in the near infrared range, allowing them to detect pressure points and spoilage in fruits that are not visible with the naked eye.
              • Higher bit depth: In general, monochrome cameras also support higher bit depths, which translates into a higher volume of data to be transmitted. This is especially relevant for applications in the area of web inspection, sorting and packaging and transportation. The hard numbers: Raw Bayer data is often transmitted at 8 bits, while monochrome data is transferred at up to 12 bit.
              • And last but not least, monochrome cameras are more affordable than color cameras.
              When is color the right choice?

              For situations where color is required, monochrome cameras can also be retrofitted using a color filter mounted in front of the lens. For black and white photography, for example, a red filter is often used on landscape shots to compensate for the green of the vegetation and the blue of the sky. Color filters can be used to target specific colors, such as during foodstuff inspection or when sorting mining products.

              Want to read more on this topic?

              Monochrome cameras such as the Basler racer are used for a variety of applications, such as in the fields of web inspection, sorting & packaging and transportation. An overview of the range of applications can be found here or in our Marketing Note "Basler racer – The Clever All-Purpose Line Scan Camera".

              A typical camera application with a monochrome camera, our Basler racer raL6144-16gm, is described in the Success Story "Easy Printed Circuit Board Traceability with Basler racer GigE Cameras”.

              If you have any further questions, please don't hesitate to contact our Basler Sales team.

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