Figure 1.

Comparison of photon-counting analog and video-based digital densitometry. A 0–2.0 OD linear beam splitter (Edmund Scientific 41960, Edmund Scientific, Barrington, NJ) was scanned with an Ortec 4310 densitometer (Ortec, Oak Ridge, TN), giving a direct OD read-out, and also with a COHU CCD camera and JAVA system, producing a digital image. The pixel intensity along the wedge axis was converted to OD by the transform OD = log(255/pixel intensity). The two methods deviated only at high OD values, below a pixel intensity of 10, where the error due to precision of measurement (±1 pixel value) becomes progressively more significant.