The computer screen photo-assisted technique (CSPT), a recently reported method for characterization of colorimetric assays, has been modeled and the ability of the technique to retain key spectral features has been determined. The robustness of CSPT to operate with different kind of screens is demonstrated and a physical explanation of the result is provided. Simulated CSPT transmittances corroborate experimental results, and enable comparison with standard methods for qualitative and quantitative evaluation. © 2004 Elsevier B.V. All rights reserved.