This conversion chart allows for a quick approximate conversion of exposure factors when changing from one known speed screen to another.

Example: If the exposure factors for an AP knee with high-speed (400) screen is 4 mAs @ 70 kV, and a 100-speed detail screen is to be used, how much of an increase in mAs is required?

Answer: Find the conversion factor by looking down the 400-speed column to the 100-speed row and locate the conversion factor of 4. 4 mAs × 4 = 16 mAs.

To check your answer, convert back from the 100 to the 400 screen technique by looking down the 100 column to the 400 row, for a conversion factor of. 25. 16 mAs ×.25 = 4 mAs (original mAs).