What is the proper light to read API tests under?

[Dnic]

When I read my test results under compact fluorescents, the pH readings are 8.2. When they are read under incandescent bulbs, the reading is 8.4. What bulb do I believe??

First pic fluoros, second pic incandescent.

 

The manuals don't mention anything, just 'bright light.'

[gabe_j]

If you can use as close to noon time sunlight. Not direct but that color temp aprox 6500k I just use light coming in from a window.

[Ekisu]

I read mine under incandescents. They produce a fuller color spectrum then most flourescents. You can't go wrong with sunlight though

[moonlitsomernite]

When doing pH readings for pools, it is always recommended to read the results facing in a bright north sky. I'm sure it's the same for aquariums. As suggested above, reading from a window would work just as well.

 

I read mine under incandescents. They produce a fuller color spectrum then most flourescents. You can't go wrong with sunlight though