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The effect of lens choice on the 5D3's AF
#1
See the [url="http://www.canonrumors.com/files/eos5dmkiii-im-c-en.pdf"]user manual[/url] p.79 to p.84.



While I must confess I'm disappointed to see such a big effect of the lens used on the AF system I'm amused to see the 50/1.8 in group A while the 800/5.6 is in group F and the 1200/5.6 in group G.
#2
[quote name='Yakim' timestamp='1333144965' post='17195']

See the [url="http://www.canonrumors.com/files/eos5dmkiii-im-c-en.pdf"]user manual[/url] p.79 to p.84.



While I must confess I'm disappointed to see such a big effect of the lens used on the AF system I'm amused to see the 50/1.8 in group A while the 800/5.6 is in group F and the 1200/5.6 in group G.

[/quote]



Well, this isn't really news. The usable AF points have always been dependent on the speed of the lens. As such I don't really spot any big surprises. The macro lenses may not fit in upon first view the effective aperture gets smaller and close focus distances.

Group F and H has probably more to do with optimization rather than original capabilities.
#3
The 1200/5.6 is a FD era lens design so I wonder if that might have some impact. While I haven't checked exactly, isn't the 5D3 AF supposed to cover a wider area than before? Thus it may show up edge limitations that were not possible to be seen before.



The only small surprise I have is the existence of group H, although it only applies to two ancient low end lenses and as such not likely to be used on this camera anyway.



Now, is it too much for me to hope they shoehorn this AF system (or similar) into the 7D2?...
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
#4
Rather than the AF issues, I find it (still) disappointing that the spot metering is only valid for the center spot...
#5
[quote name='Klaus' timestamp='1333186675' post='17208']

Well, this isn't really news. The usable AF points have always been dependent on the speed of the lens. As such I don't really spot any big surprises. The macro lenses may not fit in upon first view the effective aperture gets smaller and close focus distances.

Group F and H has probably more to do with optimization rather than original capabilities.

[/quote]



Looking closer it is evident that the max aperture of the lens has little effect on the rating of the lens WRT these grouping. Even the motor is not a clear indication. Here are f/2.8 examples:





The 135/2.8 (AFD) is in group A.

The 20/2.8 (ring USM) is in group B.

The 100/2.8 L (ring USM) is in group C.

The 28/2.8 (AFD) is in group D.

The 100/2.8 (ring USM) is in group E.
#6
I had a thought, what is the maximum magnification of those lenses? A f/2.8 macro lens is effectively f/5.6 at 1:1. So as you get closer to maximum magnification, the more you lose.



Am I bored enough to work out this table?... maybe after a quick drink of tea!



Edit: just did it, didn't give anything either. Excluding the macro lenses, the others were all 0.12x-0.14x for effective max apertures at close focus of near enough f/3.2.
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
#7
[quote name='PuxaVida' timestamp='1333193723' post='17211']

Rather than the AF issues, I find it (still) disappointing that the spot metering is only valid for the center spot...

[/quote]

I do not get why one would want the spot metering to take place at the focus point. Spot metering meters for mid tones.
#8
[quote name='Brightcolours' timestamp='1333196890' post='17215']

I do not get why one would want the spot metering to take place at the focus point. Spot metering meters for mid tones.

[/quote]



And if so, is that an issue?
#9
You can always set exposure compensation as appropriate if your subject is far from a middling level.
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
#10
[quote name='popo' timestamp='1333205065' post='17220']

You can always set exposure compensation as appropriate if your subject is far from a middling level.

[/quote]

And that is handy why? Easier and faster to meter on a mid tone and focus on a subject. If you don't have time for that, you do not have time to judge and set exposure compensation...



Most people do not seem to get metering. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/unsure.gif' class='bbc_emoticon' alt=':unsure:' />
  


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