DIY Color Densitometer


Posted on Feb 6, 2014

A densitometer is one of the most valuable tools a darkroom enthusiast can employ. Up until recently, however, densitometers were expensive and bulky. Furthermore, densitometers which would talk to your computer and calculate effective film speed, contrast index or gamma were beyond the reach of almost all amateurs. Easily programmed microprocesso


DIY Color Densitometer
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rs and the availability of highly accurate, inexpensive photodiodes make it possible for the photographer to build a densitometer which is reliable, accurate and inexpensive. The unit described here uses a new RGB photo-sensor, actually a 64 photodiode matrix with an incorporated light to frequency converter, the Texas Advanced Optical TCS-230 to greatly simplify the task. We chose to use the Basic Stamp II from Parallax Inc. as the microcontroller for this project since the device is relatively easy to program (it can be programmed right on the densitometer circuit board without having to be removed). If you ever get bored with the densitometer application for the Basic Stamp II you can always press it into service in another device. An outline of the Computing Densitometer is shown below: The outline above shows the several control lines from the Basic Stamp II to the TCS230 photo-receptor. The TCS230 integrated circuit has five input lines: two for color measurement, two to control the TCS230 electronic iris, and an Output Enable line (/OE). There is one data line and, of course, power and ground lines. The design presented in this article uses the Basic Stamp II to talk  to your computer via its serial port, placing the data directly into a Microsoft Excel spreadsheet. Parallax makes available free to users of the Basic Stamp an Excel Macro which accepts the data into your PC from. The macro, StampDAQ can be downloaded...




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