(This article is a supporting part of our ongoing testing of low-light camera metering reliability)
The Canon 1D Mk. IV has the best low-light metering ability of any DSLR we have tested, though it is still a couple stops worse than the best mirrorless cameras. It first fails to compensate at least 2/3 stop for a 1 stop decrease in light at EV-4.3, which is approximately equivalent to the light level provided by an 67% moon. At scenes darker than EV-5.7, its images are over one stop darker than those auto-metered at EV0. Compared to other cameras, the metering of the 1D Mk. IV has a smooth roll off starting around EV-2. Canon reports that its metering limit is “EV0 at 23°C/73°F with 50mm f/1.4 lens at ISO 100.” Our test shows that the camera performs well darker than that.
Like all DSLRs, the Canon 1D Mk. IV stops down the lens to take the photo, but leaves it wide open the rest of the time. In our test, its metering performance improved when used with a lens faster than f/2.8. Some DSLRs do not improve when using lenses faster than 2.8.
The Canon 1D Mk. IV has no flexibility for when to increase the ISO vs shutter speed in Auto ISO mode. The maximum allowable ISO can be set, though.
The plot shown above was created using the usual EF-mount Rokinon 50mm f/1.4 at f/2.8. The aperture-dependent metering phenomenon was tested by setting that lens to f/2 and f/1.4.
Integrating Sphere & Camera Metering Test Project