The apertures marked on lenses are correct ONLY when you focus at infinity. For macro & close-up photography, the ACTUAL APERTURE is smaller than what's marked on the lens. To correct this, you need to adjust the exposure settings suggested by your light meter (unless you have thru-the-lens metering).

This 3.5" x 5.5" laminated cheat sheet gives the exposure adjustments (increased exposure times or larger aperture openings) that you need to use for image magnifications from 1/8 to 3 times life size. Focal lengths covered range from 50mm - 450mm lenses. Lens-to-subject focus distances for each lens at each magnification are provided. You simply measure this distance and match it to the card to get the required exposure adjustment.

Although used primarily with view cameras, this card is applicable to ANY camera format (35mm, medium format, or view cameras) where you don't have thru-the-lens metering.