Ocean Optics Dragon - Manual (Page 18)

Chapter 3: Quantum Software Icons
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Absorbance is the inverse of transmission, but on a log scale. When you select Absorbance mode the y-
axis changes to a log scale of Absorbance number. So an absorbance number of 1 is 10 times less light
getting through than reference. An absorbance number of two is 100 times less.
Absorbance is normally measured at the wavelength of maximum absorption, called “Lambda Max”,
written
λ
max.
The Absorbance scale goes up to 3. Above 3 the solution is so dark that Absorbance is no
longer possible to measure reliably.
Smoothing
Average scans
This averages over a number of complete scans. For low level light sources this can improve the signal to
noise ratio. For bright sources it is normally not required.
Pixel smoothing
This technique averages a group of adjacent detector elements. A value of 6, for example, averages each
data point with 3 points to its left and 3 points to its right. This average rolls along the array.
The greater this value, the smoother the data. For chemical absorbance experiments a default setting of 5
is set, but this can be changed. For looking at emission peaks the pixel averaging width should be zero to
maximise resolution.
For absorbance measurements, high resolution is not required, so smoothing makes the spectrum easier to
see and can reduce errors. Setting the pixels to average above 5 is not normally necessary.