In any statistical study of characteristics of meteors with data obtained from photographs, corrections must be made for two inherent biasing effects due to the brighter trails left by meteors of greater mass and/or by meteors of greater velocity relative to Earth's atmosphere. In the past, attempts have been made to correct for both biasing effects with a weighting factor inversely proportional to the square of the meteor velocity relative to atmosphere. A new analysis has been made to investigate the magnitude of the weighting factor, specifically for application to photographic meteor data published by Smithsonian Institution Astrophysical Observatory. As a result of this analysis, a revised factor was obtained to operate upon actual counts of photographic meteors within various classes of velocity to provide a correct ratio of counts for all velocities reduced to any given lower mass limit. In the analysis, an expression was derived theoretically for maximum effective exposure on the photographic plate produced by a meteor in terms of the original mass of the particle, its velocity relative to Earth's atmosphere, and the angle of its path to the zenith. The expression for maximum effective exposure was tested and revised by application to 100 test meteors that were believed to have provided approximately uniform effective exposure density. The revised expression for maximum effective exposure was combined with a widely accepted equation for the influx rate of meteors of mass greater than a stated value to obtain approximately the desired weighting factor. The manner of the combination eliminated mass of the meteor particle from the factor. The analysis indicated a large change in value of the exponent of velocity relative to Earth's atmosphere in the weighting factor, namely, from -2 downward at least to -3.85 and possibly as low as -4.22. Application of the new factor should cause a significant reduction of estimates of average meteor velocities relative to the atmosphere. Extensive changes would also be required in estimates of other parameters that might bear a systematic relation to meteor velocities.