Lecture Notes: Exposure Maintenance Formula

Introduction

• Exposure Maintenance Formula is also known as the Density Maintenance Formula.
• Example numbers are taken from the exposure lecture handout.
• Steps will be fully worked through; no need for the handout.

Identifying Variables

1. Identify Variables

   • Given: (Variables) SID1, mAs1, SID2
   • Example: SID1: 40 inches, mAs1: 40, SID2: 72 inches
   • Unknown: mAs2

2. Setup Variables in Formula

   • Formula: (mAs1 / mAs2) = (SID1² / SID2²)
   • Substitute example values: (40 mAs / mAs2) = (40² / 72²)

3. Cross Multiply

   • Equation after cross-multiplying:
     • (mAs1 × SID2²) = (mAs2 × SID1²)
   • Substitute values: (40 × 72²) = (mAs2 × 40²)

4. Isolate the Unknown Variable (mAs2)

   • Equation after simplifying:
     • mAs2 = (40 × 72²) / 40²
   • Simplified further: mAs2 = 129.6

Calculation Steps

• Cross-multiplying spreadsheets:
  • Top: 40 × 72² = 107,360
  • Bottom: 40² = 1,600
• Division result: mAs2 = 129.6

Final Answer

• mAs2 = 129.6
  • Recommend rounding to the nearest tenth place.
  • Check with your instructor for rounding preferences.

Summary

• Successfully solved the Density Maintenance Formula.
• Process involves identifying variables, setting up the formula, cross-multiplying, isolating the unknown variable, and solving.