A key defining principle of the Canon EOS DSLR camera system was to make it simple and instinctive. Full-time manual focus for lenses with USM focus motors fits that remit. It is useful for subjects that don’t move a great deal; the ability to simply turn the lens’ focus ring if shooting macro or landscapes was so instinctive that you might not even have realized that it was a designed feature. It also means that the lens can be manually pre-focused before you even start the AF.
When EF lenses for DSLRs were introduced with fly-by-wire focus rings, new custom settings were added to the cameras to still enable focus to be adjusted slightly once One-Shot AF was complete.
Moving to mirrorless, Canon's RF lenses have a fly-by-wire focus ring that means you can no longer manually pre-focus in Servo AF, or adjust focus after One-Shot AF locks. The custom setting for activating the focus ring after One-Shot AF finishes is still there, and has extra settings like automatic magnification that help macro shots, but pre-focus before the shot when using Servo AF was lost until recently – and even then is only possible with select RF lenses.
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Locate the lens Electronic MF menu item on a DSLR and you’ll see it is active by default, so all EF lenses with fly-by-wire focus rings can be used to adjust focus once One-Shot AF is set. Find the same setting on a Canon EOS R-series camera and it’s disabled by default. R-series cameras add a choice to enable manual focus after One-Shot AF and also magnify; with the latter enabled, the display shows a magnified view where the active AF point is once the focus ring is turned.
Recent cameras have an added electronic full-time MF option, which provides the option to pre-focus a lens when using any AF mode. However, this is limited to a subset of the RF lenses – mostly the longer telephoto zoom and prime lenses. Combining these settings adds back in much of the lost functionality of full-time manual focus – if not yet for all RF lenses.
If this article was of interest you might also like to find out more about the best Canon cameras, along with the best Canon DSLR lenses or best Canon RF lenses for mirrorless bodies.
