ISO 12232 revision: determination of chrominance noise weights for noise-based ISO calculation

Sean C. Kelly V.D.M.; Brian W. Keelan

doi:10.1117/12.582447

17 January 2005 ISO 12232 revision: determination of chrominance noise weights for noise-based ISO calculation

Sean C. Kelly V.D.M., Brian W. Keelan

Proceedings Volume 5668, Image Quality and System Performance II; (2005) https://doi.org/10.1117/12.582447
Event: Electronic Imaging 2005, 2005, San Jose, California, United States

Abstract

Three ISO speeds for digital cameras, yielding the minimum, typical, and maximum exposures recommended for use, are defined in International Standard 12232, which is under revision. The typical and minimum acceptable exposures are based upon signal-to-noise criteria, described in ISO 12232, in which visual (perceptually relevant) noise is computed as a weighted sum of variances from a luminance (Y) and two chrominance (R-Y, B-Y) channels. The weights of the two chrominance variances, C1 (R-Y) and C2 (B-Y), are in need of reevaluation because of: (1) changes in linearization procedures being introduced in the revision of ISO 12232; (2) the limited nature of the original experiment to determine C1 and C2 and (3) suspicion that the initial C1 and C2 values were too high, overemphasizing the contributions of chrominance noise to perception. This paper describes the image simulations, psychophysical experiment, and analyses conducted to determine new values for the chrominance weights to be used in the revised standard. The values obtained, C1 = 0.279 (standard error = SE = 0.025) and C2 = 0.088 (SE = 0.017), are approximately one-half as large as those in the original version of ISO 12232. Systematic variation of the weights with the color of noise-sensitive uniform areas in the scenes is observed, but the effect is small and does not have a practical impact on the standard.

Citation Download Citation

Sean C. Kelly V.D.M. and Brian W. Keelan "ISO 12232 revision: determination of chrominance noise weights for noise-based ISO calculation", Proc. SPIE 5668, Image Quality and System Performance II, (17 January 2005); https://doi.org/10.1117/12.582447

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available