Looking for a calibration light or two for a sphere from someone who already has a calibrated sphere/tube. Ideally reasonably cheap and 18650 or 21700. Ideally a low power (500-1000lm?) one and a higher powered one (5k lm?) but I’m not sure exactly what are sensible values, if I was e.g. looking to test maybe a 250-30,000lm range. Fine to pay including the cost of the light itself for you to order, or to order to you.
Also, a question for someone who knows more about sphere design than me: If I calibrated using a less powerful light, then tested a more powerful regulated light (M44, X75, etc.) then would that reading then be valid to use as calibration for a larger sphere, or is there too much generation loss?