Sir,

In response to the comment by Mahroo et al.1 on determining the accuracy of higher cut-off values of light meter readings to determine time spent outdoors vs indoors, we have evaluated the accuracy of cut-offs higher than 1000 Lux of 1200 and 1500 Lux.

The Intra Class correlation for the cut-off values of 1200 and 1500 Lux showed higher correlations between the light meter and diary recordings during the week in a school term and school holidays, compared with cut-offs of 800 and 1000 Lux (Table 1).

Table 1 Intra Class Correlation co-efficients (ICC) for cut-off values of 800, 1000, 1200, and 1500 Lux during the school term and school holidays
Full size table

Thus, we agree with the proposal that the best cut-off value for evaluating outdoor vs indoor activities is 1500 Lux instead of 1000 Lux.