Auto Focus Sensitity Questions
From the Canon user manual is states that that lenses whose maxium aperture is larger than f/5.6 the center point has cross-type sensitivity. The remaining points are horizontal-line or vertical-line sensitive. For lenses whose maximum aperture is larger than f/2.8 the center point has high-precision cross-type sensitivity about twice as sensitive as the remaining points. The remaining points are horizontal-line or vertical-line sensitive.
The manual also states that in AI Servo mode with auto AF point selection there are also 6 hidden AF points. The manual states that center top and center bottom hidden AF points are vertical-line sensitive for f/2.8 and f.5.6 lenses as with the center AF point. The remaining 4 hidden AF points are horizontal-line sensitive with f/5.6 lenses.
Q1: Of the remaining visible 8 points, which are horizontal and which are vertical?
Q2: I assume the first statement should read "..whose maximum aperture is greater than or equal to f/5.6 but smaller than f/2.8 ..."?
Q3: I assume the second statement should read "..whose maximum aperture is greater than or equal to f/2.8 ..."?
Q4: Does the camera always use the largest aperture for auto-focus-purposes?
Q5: Is that correct? The first statement above shows that the center AF point has cross-type sensitivity. Does the center AF change from cross-sensitivity to vertical-sensitivity when selecting AI Servo?
Q6: I assume that the remaining 4 hidden AF points remain horizontal-line sensitive when using a lens whose largest aperture is greater than or equal to f/2.8. Is this a correct assumption?
The manual also states that in AI Servo mode with auto AF point selection there are also 6 hidden AF points. The manual states that center top and center bottom hidden AF points are vertical-line sensitive for f/2.8 and f.5.6 lenses as with the center AF point. The remaining 4 hidden AF points are horizontal-line sensitive with f/5.6 lenses.
Q1: Of the remaining visible 8 points, which are horizontal and which are vertical?
Q2: I assume the first statement should read "..whose maximum aperture is greater than or equal to f/5.6 but smaller than f/2.8 ..."?
Q3: I assume the second statement should read "..whose maximum aperture is greater than or equal to f/2.8 ..."?
Q4: Does the camera always use the largest aperture for auto-focus-purposes?
Q5: Is that correct? The first statement above shows that the center AF point has cross-type sensitivity. Does the center AF change from cross-sensitivity to vertical-sensitivity when selecting AI Servo?
Q6: I assume that the remaining 4 hidden AF points remain horizontal-line sensitive when using a lens whose largest aperture is greater than or equal to f/2.8. Is this a correct assumption?
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Comments
f16 is a smaller opening than f2.8
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5DSR 16-35 2.8L III 24-70 2.8L II 70-200 2.8L IS II
According to Canon the visible AF points are horizontal except the center point which is also sensitive to vertical at f2.8.
http://web.canon.jp/imaging/eosd/eos5dm2/02.html
Yes, I believe that your statement is correct.
Yes, I believe that high-sensitivity kicks in at f2.8 so your statement is accurate.
For modern lenses with full EOS connection and auto-aperture that would be accurate. For adapted lenses "you" would be responsible for the task of opening the aperture for best AF results.
If Canon is saying it I believe they are the best source of information about their cameras. Otherwise I am not clear what happens with the AF sensors during AI-Servo mode.
I believe that only the center point is Cross-Type capable.
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