Questions about live view on the Canon 5D Mark 3

Started Apr 26, 2012 | Discussions thread
Severian The Lame
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Re: Questions about live view on the Canon 5D Mark 3
In reply to Sgt_Strider, Apr 28, 2012

Sgt_Strider wrote:

Severian The Lame wrote:

Sgt_Strider wrote:

Is it safe to assume that if focus accuracy is important, then I should use contrast detect?

If focus accuracy is critical (in a static scene), you should use manual focus with 10x magnification in Live View using a tripod and remote shutter release. If the scene is not static, normal PD AF beats CD handily because of the increased AF speed. With a lens that AF's well and that has proper AF MA dialed in, PD is practically as accurate as CD. With my 70-200/4 IS it's rare when there's a dime's worth of difference in focus accuracy between CD and PD AF.

Given what you have said, what's the point of using CD AF then?

  1. Some lenses don't PD AF well or consistently (especially 3rd party lenses), in which case CD AF almost always gives good, consistent results

  2. Using PD AF ("Quick Mode") is disruptive and noisy since the mirror has to flip down and you momentarily lose the Live View image. It also introduces vibration. (I'm assuming a tripod is being used, etc.)

  3. Some lenses aren't designed with MF in mind or don't have FTM. For instance the Canon 50/1.8 II has an absurdly tiny and fiddly MF ring and is a real pain to MF, especially if you have large hands; moreover, PD AF can sometimes be an adventure with this lens.

  4. CD AF is independent of lens/body calibration so it can give good results when lens calibration and/or microadjustments are inaccurate.

  5. Sometimes you get lazy and just don't want to bother messing around with 10X magnification and MF. And with some lenses experience tells you that there won't be much, if any, difference in final image quality between CD AF and the best MF anyway --wide angle lenses, for example. Keep in mind that MF results depend on your vision and LCD viewing conditions, so while MF could potentially give the best results that doesn't mean that it will.

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