Many microscope users dismiss the color microscope camera as mundane and do not consider the technology with as much thought as a low light monochrome camera for fluorescence. Although this is understandable considering the wide range of options and high degree of pricing variability in monochrome cameras, it is no excuse to dismiss the color camera evaluation process.
Many disciplines depend on accurate color such as pathology, material sciences, and forensic science – however because of budget constraints or the influence of mainstream technology, users ultimately make decisions based on interface (FireWire, USB 3.0, USB 2.0, Camera Link, etc.), software functions, or the dreaded maximum megapixel count. Although these are important, color accuracy and image quality should sit at the top of the list of items to consider!
Assuming the user has already addressed Kohler Illumination, lighting conditions, and the objective lens have all been addressed, the camera selected can have major ramifications for image analysis, image quality, and ultimately results.
In a modern microscope with infinity corrected optics, there is a highly corrected tube lens built into the microscope, which projects the final image to the eyepiece and camera. The final lens is either the eyepieces or the camera c-mount – which matches the microscope magnification to the camera chip size.
For some reason, unknown to me, c-mounts generally do not have any correction. So if you select a camera with a ½” sensor, there should be a matching 0.5X c-mount – and that convex lens has little to no correction! In theory the sensor uses the center of the lens, which has the best correction, but if someone wants the best image possible they can either use a 1X c-mount with no lens or a 1.1X APO c-mount from QImaging.
Many people are familiar with evaluating monochrome cameras based on read noise, pixel size, dynamic range, among other specifications. However, most do not consider these technical specifications when evaluating color cameras. They are critically important to a quality image!
Generally speaking, inexpensive cameras cut corners on pixel size and noise, which reduce the dynamic range of a camera. These issues will lead to an image that appears grainy with a restricted field of view. Be wary of 1/3 inch sensors and some ½ inch sensors, depending on the number of megapixels, these could lead you down the wrong path.
Small sensors are contrasted by more expensive cameras, which have larger pixels, are physically larger in area, and are more sensitive. These traits produce a beautiful image with an excellent field of view. Sensors that are 2/3 inch or larger are traits of a quality sensor.
When evaluating the output of a color camera, the simple conclusion is that there is a color picture, however, the camera doesn’t have the ability to produce purple, brown, orange, or any other intermediate color without color interpolation. On a digital camera, each pixel is assigned a color, red, green, or blue and based on the signal in neighboring pixels, the camera will produce a color image.
There are a few ways to address whether the color is correct with lighting, lenses, and alignment, however, the color interpolation algorithms are written by people. Humans. Error-prone people who do their best to faithfully represent color, but are not always perfect. Printers solve this issue with the Pantone color palette, but the same standards do not exist for digital images.
Users are left to adjust settings such as white balance and saturation to get the image on the computer monitor to represent the view through the microscope eyepeices. This is a highly subjective and error-prone process, because without a color standard such as the one used in ChromaCal, the color accuracy is left to the user – and the quality of the computer monitor. But that’s another blog post…
Even with identical hardware components, something as simple as a camera diver can influence color accuracy. Using a QImaging camera in both QCapture Suite and Image Pro Premier will produce different color.
Color differences between the two programs can, in part, be attributed to subtle differences in default image settings. However, some of the difference is built into the driver itself and depends on the author of the software program and subsequent camera driver.
Since the dawn of digital imaging the microscope sales representatives and imaging specialists at W. Nuhsbaum, Inc. have demonstrated and sold color cameras from companies such as Leica, QImaging, Jenoptik, SPOT, and many more, with several different software programs and hundreds of camera drivers.
The experience, and customer feedback, regarding color accuracy has provided each sales representative with the expertise to be able to recommend a camera and software package that will most faithfully represent the color in your image. Contact the team at W. Nuhsbaum, Inc. to learn which camera and software platform are best for your application.