Dear Roger, You can pick a light sphere for cheap than, and use the second port to mount a photodiode or spectrophotometer (i1 spectro is OK; but you can also use a Hamamatsu C12666MA or C12880MA, those are cheaper and can be mounted permanently). I use xenon flash as light source with C12880MA, to eliminate long exposures and thus avoid heat / long exposure noise problems. With tungsten source a photodiode or C12666MA is quite OK; but if a photodiode is used an additional calibration task is needed. On Mar 16, 2016, at 8:25 PM, Roger Breton wrote:
I have an OceanOptics USB4000 with a radiometrically calibrated tungsten light source too. Could that help?
/ Roger
-- Best regards, Iliah Borg LibRaw, LLC www.libraw.org www.rawdigger.com www.fastrawviewer.com