To achieve the same field of view as a 28mm lens on full-frame, what focal length would you use on an APS-C camera with a 1.5x crop factor?

• A. 18mm
• B. 28mm
• C. 42mm
• D. 85mm

Answer: (C)

To match the field of view of a 28mm lens on a full-frame sensor, you need a shorter focal length on a smaller APS-C sensor because the crop factor effectively narrows the view. The equivalent focal length on APS-C is found by dividing the full-frame focal length by the crop factor: 28 mm ÷ 1.5 ≈ 18.7 mm. So the closest practical choice is about 18 mm. An 18 mm on APS-C will give a very similar angle of view to 28 mm on full-frame.

Using a 28 mm on APS-C would still yield a wider view than the full-frame 28 mm, since the smaller sensor crops less of the scene relative to that focal length. A 42 mm or 85 mm would produce a much tighter, telephoto field of view and would not match the 28 mm’s perspective.