Pour 40D:
  • Evaluative Metering Mode: Our testing showed evaluative mode to be within factory tolerance for all lenses having a maximum aperture of f4.5 or larger (lower f number). AF lenses with a maximum aperture of f5.6 or slower (higher f number) will overexpose slightly. With an f5.6 AF lens, we recommend an exposure compensation of -2/3EV. Manual (non-CPU) lenses with a maximum aperture of f5.6 or slower (higher f number) will underexpose slightly. With an f5.6 non-CPU lens, we recommend an exposure compensation of +2/3EV.
  • Center Weighted Average (CWA) Metering Mode: Our testing showed CWA metering mode to be within factory tolerance for all lenses having a maximum aperture of f4.5 or larger (lower f number). Lenses with a maximum aperture of f5.6 or slower (higher f number) will underexpose very slightly. With an f5.6 lens, we recommend an exposure compensation of +1/3EV.
  • Partial Metering Mode: Our testing showed partial metering mode to be within factory tolerance for all lenses having a maximum aperture of f2.0 or larger (lower f number). Lenses having a maximum aperture smaller than f2.0 (lager f number) will show a shift toward increased exposure. The shift will be greater for lenses with smaller maximum apertures. When using partial metering mode, it is advisable to first take a test shot, check the histogram, and adjust exposure compensation as required. Starting points for exposure compensation are as follows: f2.8 lens: -1/3EV, f4.0 lens: -2/3EV, f5.6 lens: -1EV.
  • Spot Metering Mode: Our testing showed spot metering mode to be within factory tolerance for all lenses having a maximum aperture of f2.0 or larger (lower f number). Lenses having a maximum aperture smaller than f2.0 (lager f number) will show a significant shift toward increased exposure, with the shift increasing for lenses with smaller maximum apertures. Spot metering mode is not recommended when using a split prism focusing screen except with very fast prime lenses. However, if spot mode must be used, it is strongly advised to first take a test shot, check the histogram, and adjust exposure compensation as required.