Respectfully,why multi af points?

[upriver43]

I don't have a 7D,yet,just a 40D and 5DMK1...I really like "most" of what I see from the 7D as a better cam for bif's/action shots to replace my 40D...However all the focus complaints....I mean this most respectfully,why are so many posted images showing OOF using multi AF points using Al focus or even servo on static subjects? The only time I use multi AF points is in Al servo for BIF's in an open sky or an unclutterd background....I'm sure there are some AF problems,too many very good photogs are reporting lousy AF,but with some of the tests and posts why not go to center point AF and one shot and give it another go?...I really want the 7D but B&H is 3,000 miles away and I want to make sure the new cam doesn't have a built in problem...Bob

 

[Timarete]

I asked this same question a couple of times and got two different answers.

1) One person said (and I'm not making this up) that he liked seeing all the little squares light up in the viewfinder.

2) The other person said he was using multiple points because (in his view) it should have made focusing less work for him (he felt it was too much effort to select a point or to focus and recompose). Obviously, this view demonstrates a fundamental misunderstanding of auto-focus systems and a desire to use the 7D as a point-and-shoot.

 

[chisquared]

Like you, I use only one focus point for static subjects. Mostly the center one.

It will be interesting to see other responses here.

I think the 7D is taking a lot of heat over this issue and much of it is misplaced. I did not say all of it! Some posters with darn good camera savvy are having problems and I certainly understand that.

 

[tivoboy]

I like a center pattern, that way if the subject that I know I am centering on moves quickly their movement will still be in the focus target

 

[Tony_S]

I've done some testing since I got my 7D, and I can confirm that using all focus points (something I would never do in normal use), I get erratic results as well. The camera seems able to pick up objects well outside of the obvious focus area and locks onto them, putting the desired focus off.

In my case I was focusing on a box sitting on the carpet, and although all of the focus points that lit up were on the box, it consistently focused a few inches in front on the carpet.

Focusing on the nearest object is fairly standard behaviour, and both my 40D and 7D manuals mention it when using all focus points, but I'm not sure if this ability to pick up objects so far away from the focus area is new to the 7D.

My own opinion is that this is a major cause of the problems that people are complaining about when they are using all focus points - I've seen a lot of photos that appear to be severely front-focused.

That's not to say that I don't believe that there are some faulty 7D cameras around as well, just that the more inexperienced (not trying to be patronising) user may get caught out when using all focus points.

 

[Timarete]

I just posted this in another thread, but I'd may as well include it here too:

The AF sensors far exceed the bounds of each box you see in your viewfinder. For example (the actual sensors are the longer rectangles, which you do not see in the viewfinder). Look at the center point here:



The AF points on the 7D are all cross-type like that center one, so they're all exceeding those squares in both directions (horizontal and vertical). All Canon cameras work like this, but having 19 of these points means that much more of your frame is covered by them.

I've done some testing since I got my 7D, and I can confirm that using all focus points (something I would never do in normal use), I get erratic results as well. The camera seems able to pick up objects well outside of the obvious focus area and locks onto them, putting the desired focus off.

 

[Pat Heuvel]

My preferred poison is motorcycles. The ones that go fast (MotoGP, Superbike, that sort of thing).

Using a single focus point on my 50D allows me to control where I am focusing, particularly when panning. It is challenging, however, to keep that one point in the perfect place to hold the perfect focus.

Having groups of AF points (sorry, I don't know the 7D terminology) should allow me to retain focus on my objective and (hopefully) increase my keeper rate, since my effective focus point is now larger. Of course, judicious use of the appropriate aperture setting would help in that regard too (for example, when I have perfect focus on a brake caliper but the rider is out of focus)!

My point is that these groups should allow focus hand-off between "related" focus points without letting the lens hunt.

 

[Ian Worthington]

Sounds like you'd do well to check out some of the BIFers comments over at

http://www.birdphotographers.net/forums

i

 

[chisquared]

I've done some testing since I got my 7D, and I can confirm that using all focus points (something I would never do in normal use), I get erratic results as well. The camera seems able to pick up objects well outside of the obvious focus area and locks onto them, putting the desired focus off.

The "obvious" for the focus algorithm seems to be high contrast. Focus needs contrast and multiple focus points are going to be attracted to contrasty sections of the scene that, unfortunately, are not always what the photographer has in mind.

In my case I was focusing on a box sitting on the carpet, and although all of the focus points that lit up were on the box, it consistently focused a few inches in front on the carpet.

That could be a different issue?

Focusing on the nearest object is fairly standard behavior, and both my 40D and 7D manuals mention it when using all focus points, but I'm not sure if this ability to pick up objects so far away from the focus area is new to the 7D.

Auto focus has been around for a long time and my guess is that the 7D is hardly a revolutionary design.

My own opinion is that this is a major cause of the problems that people are complaining about when they are using all focus points - I've seen a lot of photos that appear to be severely front-focused.

I have seen that too and suspect that the focusing algorithm defaults to nearer objects when it is presented with inconclusive data.

That's not to say that I don't believe that there are some faulty 7D cameras around as well, just that the more inexperienced (not trying to be patronizing) user may get caught out when using all focus points.

Using all focus points, or even a group of focus points, often requires an experienced shooter. As a quick and popular example, when shooting birds in flight with the sky (or a similar bland background) multiple focus points are the nuts because the user will often lose the subject in the frame due to the rapid action of the subject.

I do BIF all the time and cannot get many good shots with the central focus point. I also do lots of static to almost static shots, and prefer a single focus point for those.

Just me.

 

[Pat Heuvel]

Any in particular?

 

[gracevalley]

I shoot a lot of hockey and ended up shooting part of a game with the focusing set at 19 point focus with the centre point being the starting point.(by accident) I have found that despite this going against everything I have been doing to this point with my other cameras. (30d 50d) i found that is worked very well. When you use the ae servo settings the point that you choose is the starting point for tracking your subject. I shot a girls game on the weekend and out of about 320 shots only very few were oof. I have now shot some volley ball and quite a few hockey games with this setting and have found it works very well. I have found that you need to work with the camera and try the different settings. As far as static settings go in one shot focus 19 pt af mode it may just grab the closest object so in that case I would probably use the centre point focus. either by itself or in extended mode.

 

[Tony_S]

I've done some testing since I got my 7D, and I can confirm that using all focus points (something I would never do in normal use), I get erratic results as well. The camera seems able to pick up objects well outside of the obvious focus area and locks onto them, putting the desired focus off.

The "obvious" for the focus algorithm seems to be high contrast. Focus needs contrast and multiple focus points are going to be attracted to contrasty sections of the scene that, unfortunately, are not always what the photographer has in mind.

In my case I was focusing on a box sitting on the carpet, and although all of the focus points that lit up were on the box, it consistently focused a few inches in front on the carpet.

That could be a different issue?

Focusing on the nearest object is fairly standard behavior, and both my 40D and 7D manuals mention it when using all focus points, but I'm not sure if this ability to pick up objects so far away from the focus area is new to the 7D.

Auto focus has been around for a long time and my guess is that the 7D is hardly a revolutionary design.

My own opinion is that this is a major cause of the problems that people are complaining about when they are using all focus points - I've seen a lot of photos that appear to be severely front-focused.

I have seen that too and suspect that the focusing algorithm defaults to nearer objects when it is presented with inconclusive data.

That's not to say that I don't believe that there are some faulty 7D cameras around as well, just that the more inexperienced (not trying to be patronizing) user may get caught out when using all focus points.

Using all focus points, or even a group of focus points, often requires an experienced shooter. As a quick and popular example, when shooting birds in flight with the sky (or a similar bland background) multiple focus points are the nuts because the user will often lose the subject in the frame due to the rapid action of the subject.

I do BIF all the time and cannot get many good shots with the central focus point. I also do lots of static to almost static shots, and prefer a single focus point for those.

Just me.

I'd agree with all of that

 

[Timarete]

It's like the OP said, for anything moving on an uncluttered background, using multiple points makes sense (that's what those modes were designed for: tracking). Whether it's picking out a hockey player against a background of white ice or a bird against a blue sky, the premise is the same. You're using multiple points as they are intended to be used.

For all other purposes, using multiple points is counterproductive.

I shoot a lot of hockey and ended up shooting part of a game with the focusing set at 19 point focus with the centre point being the starting point.(by accident) I have found that despite this going against everything I have been doing to this point with my other cameras. (30d 50d) i found that is worked very well. When you use the ae servo settings the point that you choose is the starting point for tracking your subject. I shot a girls game on the weekend and out of about 320 shots only very few were oof. I have now shot some volley ball and quite a few hockey games with this setting and have found it works very well. I have found that you need to work with the camera and try the different settings. As far as static settings go in one shot focus 19 pt af mode it may just grab the closest object so in that case I would probably use the centre point focus. either by itself or in extended mode.

 

[MarkNicholas]

My understanding is that multi-points are useful when using AI-Servo to keep track of your subject. The multi AF points take over as the subject moves. If you used a single point only for AI-Servo then you need to be able to accurately follow the subject making sure the single point is always on the subject.

 

[reginalddwight]

Multi-AF points can be helpful for static subjects but probably are best suited for dynamic subjects in AI Servo or AI Focus modes.

The real puzzler is why some people favor shooting static subjects in AI Servo rather than One Shot. I just re-read Rob Galbraith's take of the 7D, and he says the following, "Static autofocus was excellent, using Spot AF, various AF points, AI Servo (we almost never use One Shot) and a small batch of different lenses."

 

[Julio]

Multi-AF points can be helpful for static subjects but probably are best suited for dynamic subjects in AI Servo or AI Focus modes.

The real puzzler is why some people favor shooting static subjects in AI Servo rather than One Shot. I just re-read Rob Galbraith's take of the 7D, and he says the following, "Static autofocus was excellent, using Spot AF, various AF points, AI Servo (we almost never use One Shot) and a small batch of different lenses."

Personally I like the extra precision of the center point in Spot AF and focusing with the shutter button. Which means I often focus lock and recompose. This only works in AI Servo mode if you focus with your thumb on the AF button and let go to recompose.

I think this is what RG is referring to when he says he never uses single shot for static subjects and it can be done in any AF mode but, once again, the center point has more precission with fast lenses than the other 18 points.

--
http://fotoman99.smugmug.com/

 

[reginalddwight]

Multi-AF points can be helpful for static subjects but probably are best suited for dynamic subjects in AI Servo or AI Focus modes.

The real puzzler is why some people favor shooting static subjects in AI Servo rather than One Shot. I just re-read Rob Galbraith's take of the 7D, and he says the following, "Static autofocus was excellent, using Spot AF, various AF points, AI Servo (we almost never use One Shot) and a small batch of different lenses."

Personally I like the extra precision of the center point in Spot AF and focusing with the shutter button. Which means I often focus lock and recompose. This only works in AI Servo mode if you focus with your thumb on the AF button and let go to recompose.

I think this is what RG is referring to when he says he never uses single shot for static subjects and it can be done in any AF mode but, once again, the center point has more precission with fast lenses than the other 18 points.

--
http://fotoman99.smugmug.com/

Thanks for the explanation, Julio. I saw in an earlier post that you seem to prefer Spot AF with the center point. Nice, tack sharp photo of your daughter. ;-)

 

[Robfix53]

I shoot a lot of hockey and ended up shooting part of a game with the focusing set at 19 point focus with the centre point being the starting point.(by accident) I have found that despite this going against everything I have been doing to this point with my other cameras. (30d 50d) i found that is worked very well. When you use the ae servo settings the point that you choose is the starting point for tracking your subject. I shot a girls game on the weekend and out of about 320 shots only very few were oof. I have now shot some volley ball and quite a few hockey games with this setting and have found it works very well. I have found that you need to work with the camera and try the different settings. As far as static settings go in one shot focus 19 pt af mode it may just grab the closest object so in that case I would probably use the centre point focus. either by itself or in extended mode.

I shoot a lot of football and, like hockey, there are very few times there are not multiple players in the field of view. Multiple focus points usually insure the wrong player is in focus, not the one I intended. Or sometimes the grass.... The center or single focus point for sports seems the only way for me. I am also amazed that you can get almost 320 shots in focus. I've never had anything like that rate of success!!!! However, I'm in Texas and Friday nights under the lights is really tough to get ANYTHING in focus!

 

[gracevalley]

I think one of the reasons I had so many keepers is that the uniforms and logos of the girls were very conducive to good focusing and also since the girls were smaller and not quite as quick it seemed easier to keep one in focus. I also have the tracking speed set all the way left or as slow as it goes which means once you lock onto one player it will not immediatly jump to another even if they skate thru the frame. The rink was also a very well lit one which helps. There was no advertising on the rink boards which helps because sometimes focus will jump to the ads.

 

[Ian Worthington]

Any in particular?

This series of threads by Arash caught my eye:

http://www.birdphotographers.net/forums/showthread.php?t=46748
http://www.birdphotographers.net/forums/showthread.php?t=46945
http://www.birdphotographers.net/forums/showthread.php?t=48419
http://www.stanford.edu/~ahazeghi/Photos/EOS7DAF/

i