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Archive 2014 · important info about 7D mk II Outer Focus Point Behavior

  
 
gschlact
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p.1 #1 · p.1 #1 · important info about 7D mk II Outer Focus Point Behavior


[B]******** IMPORTANT FYI ********* (copied from other post)

This is a GREAT and CRUCIAL piece of information about the 7D ii AF!!!![/B]

From review by Bryan Carnathan

http://www.the-digital-picture.com/Reviews/Canon-EOS-7D-Mark-II.aspx

Originally Posted by Methodical & MagicMikey View Post on POTN

This part of the review caught my attention. I wander if this could be causing some of the AF issues (note: read the entire passage and not just the red portion).

(QUOTING His REVIEW)

An apparently undocumented attribute of the outer AF points (at least in single AF point mode) is that they all can use contrast information under the next AF point toward the center, causing the adjacent AF point to functionally appear as a focus assist-like point. When contrast becomes weak (or even non-existent) on a selected outer AF point and the next point down/up (for top/bottom AF points) or left/right (for right/left AF points) has good contrast, the 7D II will auto focus using the position of that particular assist point. Here is a pair of examples:

Canon EOS 7D Mark II Outer AF Point Attribute

No Contrast | Low Contrast

I created a white canvas in Photoshop and then created two vertical bars spaced to fall under the rightmost AF point and the next point to the left. The camera is unable to focus on the white canvas (no contrast available), but can easily lock focus onto the black bars. I then reduced the opacity of the right bar until the stronger-contrasting bar under the adjacent focus point took over the camera's attention. The 7D II was tripod-mounted and positioned at an angle to the display to better discern the camera's selected point of focus. Shown in the examples is a screen capture from DPP showing the selected AF point and the area where the LCD display's pixels are most in-focus. The bar under the right-most AF point is still visible in the "Low Contrast" example, but the camera focuses similarly on the strongly contrasting bar to the left.

Corner AF points (including the corner points in the slightly enlarged center section of AF points) utilize contrast information under the two adjacent points.

Whether the outer AF points are simply larger than the point indicator or the adjacent AF point is actually being used, I cannot say. Whether this feature is beneficial or problematic is dependent on the situation you are shooting in. It was somewhat problematic in the horse example I've been showing as the bouncing ears and mane did get the 7D II's attention sometimes. The 5D Mark III's AF system does not exhibit this behavior, but the 5D III's outer AF points are farther from the borders than even some of the 7D II's next-to-outer AF points...

(END QUOTE From Review)

-------------

MY Comment:

I didn't see the image link for the example you created in PS. I am curious whether DPP indicated the outer or the assist point as the active focus point? My guess is the outer point is indicated as active which would drive most crazy. (this is my segway to the following...)

Lastly, WHERE in the menus does Canon provide the ability to turn off this automatic behavior of Use-AF-assist-point-with-outer-or-top-focus-points? This option MUST BE PROVIDED. The photographer must know that he is not getting focus where he intended!!!

Happy Shooting,

Guy

( gschlact )



Nov 26, 2014 at 04:29 PM
Imagemaster
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p.1 #2 · p.1 #2 · important info about 7D mk II Outer Focus Point Behavior


This does not seem much different to any Canon that I have owned. When multiple points are used, the point that sees the most contrasty subject will lock on that subject. This is the simple reason why we don't use multiple points when tracking a BIF against a busy background.

Even with just expanded centre-point, and the centre-point fixed on the subject's head, I have seen an expanded point grab onto a more-contrasty object in the background.

Is this not the same thing, or am I missing something?



Nov 26, 2014 at 06:32 PM
gschlact
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p.1 #3 · p.1 #3 · important info about 7D mk II Outer Focus Point Behavior


Imagemaster -
You missed the KEY distinction, this occurs when the camera is in SINGLE AF Point mode, AND the camera is using a different point for focus in these conditions.



Nov 26, 2014 at 06:41 PM
Imagemaster
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p.1 #4 · p.1 #4 · important info about 7D mk II Outer Focus Point Behavior


My mistake. Will have to test that when I get the time.


Nov 26, 2014 at 06:49 PM
EB-1
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p.1 #5 · p.1 #5 · important info about 7D mk II Outer Focus Point Behavior


gschlact wrote:
Whether the outer AF points are simply larger than the point indicator or the adjacent AF point is actually being used, I cannot say.


Oversized AF points are par for the course. Is there any indication from Canon that it is any more than size/alignment?

EBH




Nov 26, 2014 at 11:07 PM
mmurph
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p.1 #6 · p.1 #6 · important info about 7D mk II Outer Focus Point Behavior


I tested the "spot" single point AF and standard single point AF. I tested the center point and points to the side.

The behavior was consistent for all points, and for both the spot and standard AF points. The spot AF point grabbed focus just a bit outside of the box. The standard grabbed focus a little further outside of the box than the spot.

I just used a blank wall and a door frame/picture frame to test when it would acquire focus.

There was no difference in behavior that I could see between the different points, central or to the sides.

This is all "SOP" - Standard Operating Procedure for Canon cameras. Here is a discussion I found for the Canon 7D. 5 years later, the Canon 7DII is behaving exactly the same way:




AF Point Size

The squares that you see in the viewfinder of the EOS 7D* to indicate the AF points don’t show the true size of the AF point. In reality, the area covered by the AF sensor is larger than the square.

* I suspect this applies to all EOS cameras, not just the EOS 7D. But I haven’t found any information to confirm this.

You can’t do anything about this on other APS-C cameras. But the EOS 7D lets you both expand or decrease the area covered by the AF point.

Spot Autofocus

In Spot Autofocus, you select an AF point and the camera tries to focus on a smaller area than usual. A small square is displayed within the AF point square to indicate that you are using Spot Autofocus (the actual area covered by the AF sensor is still a little larger than the AF square, even with spot autofocus activated).


http://www.andrewsgibson.com/blog/2013/03/understanding-eos-autofocus-the-eos-7d/


It is just a matter of learning how the tools work ... These are pretty sophisticated tools! There are some Canon videos available, as well as an auto focus guide for the 7DII very similar to the 46 page guide for the 1DX and 5D3.









Nov 27, 2014 at 12:23 AM
Imagemaster
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p.1 #7 · p.1 #7 · important info about 7D mk II Outer Focus Point Behavior


mmurph wrote:
It is just a matter of learning how the tools work ... These are pretty sophisticated tools! There are some Canon videos available, as well as an auto focus guide for the 7DII very similar to the 46 page guide for the 1DX and 5D3.


In other words, the 7D2's AF is working just like it is supposed to, and has on previous models, and we can ignore this:

Lastly, WHERE in the menus does Canon provide the ability to turn off this automatic behavior of Use-AF-assist-point-with-outer-or-top-focus-points? This option MUST BE PROVIDED. The photographer must know that he is not getting focus where he intended!!!



Nov 27, 2014 at 12:51 AM
mmurph
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p.1 #8 · p.1 #8 · important info about 7D mk II Outer Focus Point Behavior


Imagemaster wrote:
In other words, the 7D2's AF is working just like it is supposed to, and has on previous models, and we can ignore this:


EXACTLY!

"Same as it ever was ..." - to quote David Byrne

"Much Ado About Nothing" - to quote ... uh ... someone else.






Nov 27, 2014 at 03:11 AM
gschlact
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p.1 #9 · p.1 #9 · important info about 7D mk II Outer Focus Point Behavior


Mmurph,
I respectfully dissagree. To me, I think your test was not the same issue as the one mentioned in the review link, and image test. First, the review was specific to outer most points only, and was not about af point size only.(did you see the image he used for his test)? With his, he had already confirmed the working outer most point with camera on tripod. Then he faded the vertical line and saw the dog jump to the closer lime and AF point.

If you don't agree, the difference is only a matter of am an shot.







Nov 27, 2014 at 09:10 AM





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