STOUFFER T2115 21 STEP GUIDE
The best exposure test for basic exposure hardness is a Stouffer 21 Step Transmission Gray Scale, a 5.5" camera film positive opaque at one end, and clear at the other, with 21 steps in between. The 21 steps simulate 21 different exposures and you get visual feedback to make clear judgements without guessing. Put a 21 Step on every stencil you expose for the rest of your life.
To learn more, please visit the video link below: