What is Canon DSLR 'Quick Mode' autofocus in Live View for?
Asked 1/25/2014
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On some Canon DSLRs, Live View offers 'Quick Mode' autofocus, which briefly drops the mirror to use the camera’s normal phase-detect AF system instead of contrast-detect AF on the sensor. It seems like an awkward compromise: it interrupts Live View, yet if speed matters you could just use the viewfinder, and if precision matters you could use contrast AF or manual focus. In practice, when is Quick Mode useful, and why would a photographer choose it over the other focusing options while in Live View?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
12y ago
2 Answers
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There are several reasons for this:
It is quicker as the name implies and as you figured out. "Why not use the viewfinder instead if focusing speed is important?" Because you cannot. :) At least for me, this happens mostly when I shot with my dSLR above the head (it happens in photo journalism) and hence in order to frame I use the Live View. Also, when you shot video you must be in Live View. Ok, you will cut in post the small piece where the AF is hunting/working but you have changed the focus very quickly and have a new piece of movie focused successfully elsewhere.
Low-light. Well, this is big one. There's really no comparison between the performance of PDAF (especially cross and double-cross AF points) and CDAF in low-light / low-contrast situations. And when we say 'low-light' we mean almost any indoors environment.
Flexibility. This is true especially if you have high-end AF sub-systems like in 5D3 / 1DX where you can quickly change the way in which /and the place where the dSLR focuses. That box of CDAF is quite lazy and doesn't offer area expansion / small area focusing and other such things.
But of course, if you and your subject have the time and the patience then it is better to use Manual Focus in Live View.
Originally by user952. Source · Licensed CC BY-SA 4.0
user952
12y ago
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Quick Mode exists for times when you need Live View framing but want the speed and low-light performance of the camera’s regular phase-detect AF system.
Typical uses:
- Awkward camera positions: shooting above your head, low to the ground, or otherwise where you can’t use the viewfinder.
- Low light / low contrast: phase-detect AF is often much more reliable and faster than contrast-detect AF in difficult conditions.
- Video refocusing: on cameras that allow it, you can quickly refocus using Quick Mode, accepting the brief interruption and then trimming that moment later if needed.
Why not just use the viewfinder? Because sometimes you physically can’t while still composing the shot the way you want.
Why not use contrast AF? Contrast AF can be more precise in some situations, but it is usually slower and may hunt more, especially in dim light.
So Quick Mode is basically a practical compromise: keep Live View for composition, but temporarily use the DSLR’s faster AF system when Live View AF is too slow or unreliable.
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AI12y ago
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