What is the magnification factor when SID is 42 inches and OID is 10 inches?

What is the magnification factor when SID is 42 inches and OID is 10 inches?

• A. 1.3
• B. 1.0
• C. 0.9
• D. 2.0

Answer: (A)

Magnification in radiography comes from the geometry of the setup, specifically the ratio of source-to-image distance to source-to-object distance (SID/SOD). The distance from source to object is SOD = SID − OID. With SID = 42 in and OID = 10 in, SOD = 32 in. So the magnification factor M = SID / SOD = 42 / 32 ≈ 1.3125, about 1.3. This means the image is roughly 1.3 times larger than the actual object. If there were no OID, magnification would be 1.0; a magnification of 2.0 would require a much smaller SOD (or a larger OID), which isn’t the case here.

Magnification in radiography comes from the geometry of the setup, specifically the ratio of source-to-image distance to source-to-object distance (SID/SOD). The distance from source to object is SOD = SID − OID. With SID = 42 in and OID = 10 in, SOD = 32 in. So the magnification factor M = SID / SOD = 42 / 32 ≈ 1.3125, about 1.3. This means the image is roughly 1.3 times larger than the actual object. If there were no OID, magnification would be 1.0; a magnification of 2.0 would require a much smaller SOD (or a larger OID), which isn’t the case here.