Reversed 28mm Lens Macro Magnification Scale

Lens: Tokina RMC 28mm F/2.8 reverse mounted.
Camera: Canon 400D (1.6 crop DSLR)
Image: Steel ruler 1mm divisions.

Canon 400D CMOS sensor is 22.2 x 14.8mm, subject width is a little over 11mm. "Film plane" magnification (macro) ratio about 2:1. (2X)

For macro-photography of subjects less than 7mm diameter, the reversed 28mm lens works well, set at infinity focus and around F/16 for best results.