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Archive 2012 · Looking for 5D3 AF primer

  
 
StarNut
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p.1 #1 · p.1 #1 · Looking for 5D3 AF primer


Hi,

Like the title says, I'm looking for some reasonably well-done web page that discussed the various AF options on the 5D3. I find the owner's manual a but useless in real-world applications of the various options.

Thanks.

Mark



Oct 20, 2012 at 01:57 PM
arbitrage
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p.1 #2 · p.1 #2 · Looking for 5D3 AF primer


This PDF guide from Canon is fairly good. It says 1DX in the title but if you read the footnotes it is recommended for the 5D3 as all the functions are identical.

http://www.learn.usa.canon.com/resources/articles/2012/1dx_guidebook.shtml

The download link for the PDF is at the bottom left of the page.



Oct 20, 2012 at 02:03 PM
StarNut
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p.1 #3 · p.1 #3 · Looking for 5D3 AF primer


Thanks; that looks very useful (if also very long).

I think that one thing that would really help me understand all this is that I don't understand the purpose of multiple AF points, since a lens can only focus at one distance from the lens.

Mark



Oct 20, 2012 at 02:34 PM
Ariel Bravy
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p.1 #4 · p.1 #4 · Looking for 5D3 AF primer


Sure, but is the object you want to focus on always in the same location in the viewfinder?

Will you ever be shooting a subject that's moving?



Oct 20, 2012 at 03:52 PM
arbitrage
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p.1 #5 · p.1 #5 · Looking for 5D3 AF primer


StarNut wrote:
Thanks; that looks very useful (if also very long).

I think that one thing that would really help me understand all this is that I don't understand the purpose of multiple AF points, since a lens can only focus at one distance from the lens.

Mark


I'm not sure if you mean that you don't understand why you would need 61 points to choose from OR if you mean that you don't understand why you would use a 9 pt zone or 5 or 9 pt expansion. If the former, then obviously not having to focus recompose is the main purpose. If the latter, then it depends on what you are shooting. Most of these expansion and zone modes are used for moving subjects. If you are tracking a bird in expansion mode and the centre primary point moves off the bird for a moment then the 4 or 8 assist points are designed to keep the focus on the initial subject. Zone mode gives you a group of points in a given area that will all work to try and grab the closest subject with the most contrast. This works great for subjects against plain, non-distracting backgrounds like birds against a blue sky.

My examples are all geared towards birding but I'm sure the sports shooters have their own similar uses for these multiple AF point modes.

If you are shooting still subjects, then single and spot AF modes may be all you will ever need (you can disable as many of the modes as you wish so that you never see them or cycle through them). But having a fairly large coverage area with the 61 points is a huge benefit.



Oct 20, 2012 at 07:42 PM
Killergoalie
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p.1 #6 · p.1 #6 · Looking for 5D3 AF primer


Famed Bird Photographer, and noted Canon user, Arthur Morris has written a number of user guides for several Canon cameras, including the 1Dx, and the 5D Mk III which you might find rather helpful.

They cost a bit, but knowing his experience with Canon bodies, I'm sure they're very informative.

Here's link to a page with more information:


https://store.birdsasart.com/shop/item.aspx?itemid=347



Oct 21, 2012 at 01:07 AM
StarNut
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p.1 #7 · p.1 #7 · Looking for 5D3 AF primer


Thanks for the additional information.

I understand, I think, the concept that multiple points add to the precision, I just don't understand how. The only time I really have an issue with focus is with birds at a distance; I have no idea how best to set up the AF to help track darting birds, nor do I understand how additional points somehow help to keep a little, moving object in focus (i.e., how does the AF system know that that little birdie is what I'm trying to focus on, rather than the background?). Maybe I'll get it after reading the stuff you guys have referred me to.



Oct 21, 2012 at 12:58 PM
matt4626
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p.1 #8 · p.1 #8 · Looking for 5D3 AF primer


++Art Morris


Oct 21, 2012 at 03:53 PM
timbop
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p.1 #9 · p.1 #9 · Looking for 5D3 AF primer


StarNut wrote:
Thanks for the additional information.

I understand, I think, the concept that multiple points add to the precision, I just don't understand how. The only time I really have an issue with focus is with birds at a distance; I have no idea how best to set up the AF to help track darting birds, nor do I understand how additional points somehow help to keep a little, moving object in focus (i.e., how does the AF system know that that little birdie is what I'm trying to focus on, rather than the background?). Maybe I'll get it after reading the
...Show more

If you only use 1 point during AI servo, then you have to keep the AF "over" the bird while it is flitting and swerving. Since that is tough to do, they allow you to make the camera more flexible. When you "expand" the AF points, the camera uses the one selected point to achieve initial focus - say at a distance of 60 feet. Then if the bird moves out of the area covered by that point, the camera software analyzes if any of the points surrounding the selected point have something in focus at 60 feet or so (since the object now covered by the initial point is the tree 120 feet in the background (again an example). If the camera does find something in focus at roughly 60 ft, then it assumes the bird has moved to that point and thus it uses the adjacent point instead of the selected point. In the case of the 1dx it also uses color to track if the object it thinks is the bird is not (i.e. if the initial lock was a white bird and the other point found green it is ignored).

Obviously this is a simplification, as many factors come into play when there are many objects at roughly the 60ft distance, and also the fact that the bird may be moving toward or away from you. That is why tracking a slow bird that moves in a straight line across a clear sky is easiest to track - a small bird in a marsh with reeds in the foreground is much harder, as are athletes running erratically on a crowded field. To help with those tough situations, the camera settings set by the user help the camera to more correctly chose the subject from the noise.



Oct 22, 2012 at 07:40 PM





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