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Apple Aperture has a function "Show Focus Points". When I am using it with raw files from Canon 500D, it displays the pattern of focus points (just like the camera viewfinder) and highlights some of them.

First I thought that it would do the obvious thing: it would just show which focus points were active (either the focus point that was selected manually, or the focus points that the camera selected automatically).

However, the results did not seem to match the reality; there were some red rectangles, but they seemed to be in the wrong places. And then I had a bit closer look at the display and realised that there are (at least) four different kinds of rectangles:

  • thin white
  • thick white
  • thin red
  • thick red

What do these different symbols mean? Not all of them are visible in all photos, but I was able to find photos that actually had all four types of rectangles.

I would guess that one of the following explanations is close to the reality:

  1. thick rectangles (both white and red) show the focus points
  2. thick white rectangles show the focus points.

But what do the colours mean, then?


Edit: Here is a quick test shot that shows what I see. I had set the camera to automatically select the AF points. According to the flashing lights in the viewfinder, the camera selected the center point (= thick red) and the lower right point (= thick white). But then why is the rightmost AF point shown as a red box?

example

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Can't it also symbolize that the center focusing point should is cross-type (sensitive to both horizontal and vertical contrast changes)? –  che Jan 1 '11 at 20:06
    
@che: It would have been too easy if, for example, the center point was always red (or thick). But this doesn't seem to be the case. –  Jukka Suomela Jan 1 '11 at 20:16
1  
I poked around for a while on this and there's not a lot out there, but I did manage to dig up two separate (but not 'official Apple') forum threads on 'teh interwebs' where users were experiencing the same thing and having the same question with the Canon 500D. Responses seem to suggest this is a bug exclusive to the Canon 500D specifically. Wasn't really enough for me to feel comfortable committing to an answer on, but thought it might add to the overall discussion... –  Jay Lance Photography Jan 1 '11 at 22:28
1  
Assuming for the moment that it's NOT a bug, it does make me think we could 'reverse engineer' the purposes of the different colors by shooting some test shots. What happens if you manually select a focus point, for example? –  Jay Lance Photography Jan 1 '11 at 22:44
1  
The part in the posts I found that made my little mind go 'hmmm' was that they both mentioned a thin red rightmost focus point that never changed, and that's what your photo showed too. If you're seeing that on lots of photos it sure seems like additional circumstantial evidence of bug-like behavior. :-) –  Jay Lance Photography Jan 1 '11 at 23:37

3 Answers 3

up vote 3 down vote accepted

While there is not a lot of information out there on this (and thus it is possible it is actually expected behavior), all official Apple sources describe the behavior of the "Show Focus Points" feature working as LudoMC describes in his answer, and nowhere can I find any reference to the feature working in any way like you're experiencing it. Based on that, and on forum posts elsewhere on the internet, such as this post over on dpreview.com:

http://forums.dpreview.com/forums/readflat.asp?forum=1031&message=35694723&changemode=1

I suspect that what you're experiencing may actually be an Aperture 3 bug related to the Canon 550D model camera.

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I've checked in both the Aperture help and in the Apple Aperture's Pro Book and there is no reference to focus points :-/

On my side, as I'm only using a manually selected single focus point, I've always seen a single red (thick) square which is my focus point. All others are thin white. See below:

Aperture focus points

Could you show us a picture where you have the four types on the same picture to see the pattern and try to understand?

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After messing around with some of my shots in Aperture, I think the meanings are highly camera-specific. For my 450D/Rebel XSi, they seem to mean:

  • Narrow white frame: Inactive focus point.
  • Bold white frame: Not sure; see below
  • Narrow red frame: Active, but unselected point.
  • Bold red frame: Chosen focus point. More than one can be chosen.

Whereas for three models of Canon P&S (PowerShots: SD900, SD1300 IS, and S90), bold white frames indicate primary focus points and narrow white frames indicate secondary focus points. Since these cameras don’t have fixed focus points, it makes sense that they wouldn’t have available-but-inactive points.

In general, they seem to ascend in certainty — the bolder the frame, the more certain it was to have achieved focus at that point.

Interestingly, the majority of my S90 shots have a single frame, even where there should be multiple, such as when it detects two or more faces. Perhaps it doesn’t record this when shooting RAW, or Aperture doesn’t understand how to pull that from RAW vs. the JPEGs shot by my earlier ELPHs.

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