Graeme Gill wrote:
Do you really need to go below 740 nm ?
Measurements in this region are a way to indirectly learn something about the IR sensitivity and -filtering of scanners or cameras.
The example <http://digitalproof.info/argyll/eye-one_IR_calibration/sensor_example.pdf> (unfiltered scanner sensor) might point out that an ill-suited IR filter can have disastrous consequences.
I could cope with 380...730 nm data so far, but there were situation when wavelengths > 730nm played a (unpleasant) role -- see <http://digitalproof.info/argyll/eye-one_IR_calibration/IR_example.pdf> (calculated response for the perfect diffuse reflector, black: cone fundamentals and D50, RGB: Scanner sensor with 3 different IR filters and broadband fluorescent illumination).
You might be right: /if/ there are influences from beyond 730nm, there is no need to measure them very precisely to detect that there's something wrong.
But as I have to measure a vast number of samples in the near future, I want to make sure to get the best possible results. I'm thinking about buying a Barbieri LFP for that purpose. It would save plenty of work and has a broader spectral range (380 ... 780nm) -- but unfortunately it's not exactly cheap.