9pt AiAF system

[agent007]

hi all,

Having disabled the AiAF, I noticed that in some pics (eg: a group of people), only one point, ie, the main subject or the centre frame where the camera was focused is very clear as compared to the surrounding area. I'm wondering, since AiAF uses a 9 point focus system, does it mean that all 9 points or atleast 6 out of 9 will be in focus as compared to the 1 point when it is disabled?

thanks

[stopbath]

No. The lens can only focus at one distance at a time. The 9 or 1 focus points are only where the camera can look to find focus.

So, the camera starts looking for focus as the lens slowly moves. WHen you use 9 point focus, the camera will look at each of those 9 spots, then move on. If you use 1 point focus, it only looks at the middle box. Once it believes it has focus it shows which box(es) it used to figure that out.

The reason for some part of the image to be not in focus could be depth of field (distance closer and further than the point of focus which are also appearantly focused), dirt on the lens, lens element out of alignment, and various other things.

[agent007]

Thanks for the reply...Just to clear up ur point. Sometimes the AiAF shows 6 boxes, doesnt that mean a more focused image on those points? or does it eventually select 1 out of the 6?

Once it believes it has focus it shows which box(es) it used to figure that out.

[stopbath]

Thanks for the reply...Just to clear up ur point. Sometimes the AiAF shows 6 boxes, doesnt that mean a more focused image on those points? or does it eventually select 1 out of the 6?

Once it believes it has focus it shows which box(es) it used to figure that out.

Manual isn't quite clear on the process. Perhaps it thinks those 6 zones were all the same focus zone... If it really chose one of those 6, I would guess it would show only one zone...

I only use a single, so I have not really worried about what it does...

[agent007]

Seems like the camera does select multiple focus points...So, there is a possibility of those points being clearer..


Canon's wide-area AiAF automatically selects one or more focusing points based on the position of the subject within the frame


http://consumer.usa.canon.com/ir/controller?act=CanonAdvantageTopicDtlAct&fcategory id=113&id=3263

[Jon]

I believe that when multiple focus points are shown, the camera averages the setting so they'll all be more-or-less in focus; it determined they're close enough together, or potentially significant enough, that it can't decide which one was most important, ands relies on depth of field to cover for them.

[agent007]

So, I think contrary to what everyone has been saying to disable AiAF, it should be enabled if one needs sharper pics...