Magnification and Effective F-number

The aperture displayed by the camera is for when the focus is set to infinity. (The MP-E65 f/2.8 1-5x lens cannot be set to infinity). The actual aperture (effective f-number) results in a darker image (f-number increases) as the subject's distance becomes shorter (magnification increases). This does not cause exposure problems for normal picture taking (the exposure problems for normal picture-taking (the MP-E 65mm f/2.8 1-5x lens cannot take normal pictures). However, for macro photograph, you cannot ignore the effect f-number.

When you use a handheld exposure meter to set the exposure, you must factor in the effective f-number.

Use the following formula to calculate the effective f-number.

Effect f-number = f-number x (magnification /1)

For example, if the aperture displayed by the camera is f/2.8 and the magnification is 1x, the effective f-number will be f/5.6 (see chart below)

Setting the Exposure

The correct exposure for a close-up shot largely depends on the subject. Thererfore, try to bracket the exposure for the same subject.

With the EOS-1 and EOS-1N

TTL autoexposure metering is possible from 1x to 5x. Select the desired picture-taking mode and check the shutter speed and aperture.

With Other EOS Cameras

Since other will be a slight exposure error using AE metering is not recommended. Take test shots first or use a handheld meter to determin the proper exposure based on the effective f-number. If youi use the f-number displayed by the camera, use the exposure factor in the table below to convert it.