You’re welcome - the Opple could just be on any stable surface. I actually was reading the numbers while I took this picture - rock stable CCT and only fourth digit change. Keeping Opple fixed is easy, it’s the light that’s difficult to keep fixed in one spot since you will be doing something with it.
Having said that, this consists of 1 run of a test, the next run it will still be stable but it may read a different number. So personally I will look for a RANGE for anything I measure. And once I’ve done it enough I know this range and don’t lose sleep for variation. (I have a nerdy notebook with pages of data. :person_facepalming: ). For example the 219b 4500K is around –0.010 +/_ 0.002 or so depending on the light, the GT-FC40 is around –0.006, and so on. It’s a range, but it’s stable and repeatable.
One example: comparing Duv between Convoy Green AR lens and UCL Purple AR lens.
- First run Green Duv –0.0120, Purple Duv –0.0100. X,Y coordinates rock stable.
- Second run (light and sensor at slightly different positions, on a different day) Green Duv –0.0100, Purple Duv –0.0080. X,Y coordinates different from 1, but rock stable.
In both cases Purple lens drops Duv by 0.0020. And as I do more comparison, with a different light, 519a 4500k for example, and I notice the drop remains ~0.002. At this amateur level of my hobby, personally that’s all I need to know.