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Old Jun 8, 2007, 3:29 PM   #1
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Just curious how big of a deal it is that Nikon's D40 & D40x both have a 3point focus system. I mean is that gonna be a huge difference vs. Canon XT which has 7 & XTI which has a 9point focus? It's a big number gap,but is it a big difference? What type of photography would having a 3point focus system have a negative impact? Sports/action???
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Old Jun 8, 2007, 3:38 PM   #2
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You'll have to do more focus/recompose with only 3 points. Also, in many instances with sports and wildlife shooting, people prefer to NOT use just a single point to track their subject. This is where the servo tracking capability with a 3 point system will fall behind. Some people, however prefer just using one focus point for action shots - in which case it isn't a huge deal.

To me, it's a disadvantage because you have less options for where the focus point is. When I'm shooting stills, I prefer to select the proper focus point rather than focus and recompose. But I thought 7 focus points was too few. With any luck my next camera will have 45 to choose from
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Old Jun 8, 2007, 3:56 PM   #3
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DIGuy-

I shoot with both the D-40 and the Canon XT/350D. Both cameras are fast to focus. I really don't detect that there is a huge difference in focusing, and certainly not in the camera performance on either camera. JohG is our resident sports photo expert and he has noted a difference in the sports shooting environment.

However, in my experience which is more generalized shooting, the difference has not been that much of a factor.

Sarah

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Old Jun 9, 2007, 10:21 AM   #4
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Sarah,

Just to clear up any confusion - I wasn't refering to focus SPEED. Merely the number of focus spots. In any DSLR you have to have a focus spot on your subject. When you have only 3 vs 7 or 9 then you obviously have to do more focus and re-compose.

As to the action shots - if using all focus points in a servo mode, the camera 'passes off' the subject from one point to another. With only 3 points you have a higher likelihood of the subject not being behind one of the points. If the subject IS behind a focus point the D40 may very well focus just as fast and I'm sure just as accurately as D50 or D80 I don't know. You just have less points to choose from when composing your shot and less to use when tracking a subject using all points.
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Old Jun 9, 2007, 10:37 AM   #5
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JohnG wrote:
Quote:
In any DSLR you have to have a focus spot on your subject. When you have only 3 vs 7 or 9 then you obviously have to do more focus and re-compose.
A lot of old school photographers use a focus and recompose technique without any apparent issues.

But, depending on the lens, aperture, focus distance and more, it could cause some problems. Here is one article on the subject:

http://www.mhohner.de/recompose.php

Here's another:

http://www.outbackphoto.com/workshop...y06/essay.html

Personally, I try to use the focus point closest to my subject whenever possible to limit my need to recompose.

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Old Jun 9, 2007, 10:44 AM   #6
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Another thing to take into consideration is metering. Most cameras' default muti-segment (a.k.a., matrix) metering systems heavily weight your focus point when making exposure decisions.

So, recomposing can also impact your exposure, depending on a camera's behavior with a half press (depending on whether it only locks the focus, or both the focus and exposure).

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