To stimulate a flock of breeders to start production, the increase in light intensity is just as important as the increase in light duration (day length). Preferably we have a 4-6 time increase in light intensity to get the birds in production.
This means that the light intensity in rearing should not be too high, and the light intensity in production should not be too low. To achieve this, it is important to measure or determine light intensity, but as the treshold of light is different in rearing and production, the way we measure it is also influenced.
In rearing, we want to have not more than a certain maximum in light intensity. This means that we do not want to exceed a certain intensity, for instance 10 lux. To achieve this, we measure the light intensity at the brightest point in the house, and this level should not be higher than 10 lux. Normally we do not want to have a light intensity lower than 3-5 lux, to keep the birds active and avoid leg problems. This means that we have to measure on the darkest point in the house, and there we still want to measure 3 to 5 lux. If we have to increase the light intensity to much to achieve this and we exceed the level of 10 lux at the brightest point, we have to adjust our light distribution. If our light distribution is very even, a highest level of 6-7 lux might be achievable to get 3-5 lux at the darkest spot.
In production we want to have the darkest point in the house not less than a certain minimum of light intensity, usually 20-25 lux. Also here we have to measure the lightest and darkest point in the house, but our focus should be to get the lowest intensity not lower than the minimum level that we want.