User's Manual - Cornell Lab of Ornithology - Cornell University

Chapter 3: Spectrum Analysisamplitudes appear as white. The upper cursor determines the spectrogram’s“ceiling” amplitude, above which all values are represented by black. When aspectrogram is first drawn, the amplitude floor is set to the spectrogram’sclipping level, and the amplitude ceiling is set to the highest amplitude valueon the spectrogram. 1Increasing the contrast moves the floor and ceiling closer to each other,reducing the number of shades of gray in the spectrogram. If the contrast is setto its maximum (100%) value, the floor and ceiling are equal, and thespectrogram becomes black and white (no grays). Adjusting the brightnessshifts the floor and ceiling up (decreasing brightness) or down, whilepreserving the distance between them. The initial contrast and brightnesssettings that are determined when the spectrogram is calculated are arbitrarilyassigned values of 50%.You can adjust the floor and ceiling of the spectrogram independently bymoving the amplitude cursor in the spectrum up or down.The number of shades of gray in a spectrogram may be limited by the “pixeldepth” of your monitor. You can specify the number of colors or shades ofgray that your monitor can display using the Macintosh “Monitors” controlpanel (accessible through the apple menu). The choices that are availablethrough the control panel depend ultimately on the display hardwareinstalled in your machine.1 The spectrogram’s amplitude ceiling is equal to the highest point in the spectrumonly if the spectrum happens to have been made from the time interval that includesthe highest value in the spectrogram.60 Canary 1.2 User’s Manual