Proper Way To Read Api Test Tubes

[Marnee]

When you ready your results from the test tube, do you just hold the tube up at eye level and place the chart next to the test tube, or do you invert the tube and look down through the bottom?  
I was checking my Nitrate and when I look down through the tube it is darker then holding the tube at eye level, so was wondering which method is used by other members.  

 

[fluttermoth]

Next to the chart, unless you're having problems with the ammonia test, in which case it can be useful to look down from the top, with the lid off (not upside down!) to see if there's a tinge of green in it.