Hunterlab color spectrophotometer data collection and spacing

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Question:

We have many types of HunterLab instruments throughout our organization. When looking through the literature we see that all use a 10nm bandwidth except for the UltraScanPro which uses a 5nm bandwidth. A colleague asked me to provide the spectral resolution for each instrument, I'm not sure what he is asking for me to provide.

Answer:

In simple terms resolution refers to the number of detector elements/wavelength range of light being measured. The wavelength range is the number of nanometers between the lowest measured wavelength from the highest measured wavelength. For example if the sensor measures from 400nm to 700nm then the wavelength range is 300nm. From the literature you can find the pixel count of the array. The nominal resolution for our instruments is shown below.

ColorQuest XE 300nm/128pixels = 2.34 nm/pixel

UltraScan Vis 420nm/256pixels = 1.64nm/pixel

UltraScan Pro 750nm/512pixels= 1.62nm/pixel

UltraScanXE = 390nm/40 elements= 10nm/detector *

*The obsolete UltraScanXE uses an technology comprising a group of 40 discrete detectors as opposed to a linear array of pixels.

Note that these are approximations as the projected image is slightly wider than shown such that the several of the first and last pixels are not used in the calculation. For example in the ColorQuest XE the first pixel used usually number 4 and the last one used is usually 124 so technically that would equate to a 2.54 nm/pixel resolution, but then the next sensor might map out an begin at pixel 5 and end at 126 giving a 2.48nm/pixel. Manufacturing variation in the polytube assembly and in detector mapping cause these slight differences in resolution which is why we only specify a general resolution value such as less than 2 for the UltraScan Vis and Pro and less than 3 for the ColorQuest XE is typically reported in our literature.

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