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Old May 16, 2006, 3:52 PM   #1
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I have just bought my first DSLR a 30D with a 17-85 canon lens and can not figure out the autofocus - is there such a thing as learning to autofocus? Can some help me understand the autofocus by viewing some of my photos.

I will post 4 shots taken this weekend - I have cropped them but have used the ZoomBrowser software so that it shows the 9 autofocus points and which ones are active for the photo. In the photo below, the gorilla was moving around quite a bit then sat down and I shot him. The autofocus decided to focus on the grass in front of him. He got up shortly thereafter so I did not have time to manually choose an autofocus point.
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Old May 16, 2006, 4:03 PM   #2
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In this shot I was behind the mound of sand and thus could not see the bike until it crested the mound so predictive autofocussing would probably not work and with the difference in my timing, the distance to the bike would vary with each shot. I must say that the shutter lag is almost non existent. The autofocus here has picked up the mound in the foreground and also the "tent" in the background on the right. The bike alos happened to be in between all of the points
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Old May 16, 2006, 4:06 PM   #3
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In this one the focus is along the bottom right of the focussing diamond, note that there is no focus on the light on the right
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Old May 16, 2006, 4:21 PM   #4
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The autofocus decided on the fence behind the train in this case.

I am worried that focussing may be an issue for me with this camera for moving objects but I have not seen anything about this on the web so maybe I just dont know how to manage the autofocus. Manual focus might help in some instances but the I believe that one would need a focussing screen which seems to be available only through third parties. Any comments guys?


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Old May 16, 2006, 8:37 PM   #5
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and I shot him
:shock::-)

I am no expert either, but unless somebody else finds a better way I will take the pictures the way I like. And the way I am using AF (most of the time) is just with center point. First I focus, hold the button half-way and then recompose. That way I have 100% control. I think using all 9-points is for A-mode (camera decides on everything including my diet :-)).

Other way is to work with depth of field button (setting), but I do not use that. I like to decide on my DOF.

I would use all 9 AF points only when I do not have a choice or when any of 9-points is good (low pass aircraft for example), or flat surface or whenever I do not have time to recompose (fast action).

I think Nikon D200 is somewhat better in controlling AF than D30 (opening umbrella now).


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Old May 17, 2006, 4:01 AM   #6
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I am no expert either, but unless somebody else finds a better way I will take the pictures the way I like. And the way I am using AF (most of the time) is just with center point. First I focus, hold the button half-way and then recompose. That way I have 100% control.
Which is all very well, but you can end up with a lot of out-of-focus shots that way, especially if you're using a wide aperture, which can of course lead to erroneous complaints about softness which are blamed on lenses or the camera, when in fact they are simply operator error.

The best way is to learn how your camera works under different conditions and adapt your technique accordingly.

Obviously there are 3 main methods:

1. Let the camera decide.

2.Select the correct focus point manually for the shot from the 9 available and recomposeorcrop if youneed to.

3.Use the centre point and recompose, (which is just a special case of #2).

For #2 & #3make sure you keep an eye on the aperture and keep it stopped down enough to make up for the errors you will be introducing in the focus distance by recomposing, and consider cropping instead of recomposing if you're not sure your aperture will be small enough to give the depth of field you want.

As to D200 v 30D - well, they're both excellent cameras, but the reviews I have seensuggest exactly the opposite of what you say: i.e. the Canon is a*marginally* better action camera with slightly faster and more accurate AF and better high ISO performance. The D200 of course has other advantages over the 30D that gives it an overall higher rating.
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Old May 17, 2006, 10:54 AM   #7
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Flash99, camera is dumb, it doesn't know where your subject is. So you should decide which AF point to use and put that AF point on the spot which you wnat to have in focus. Like for people/animal shots, you may want to focus on the eye, so you put your selected AF point on the eye.

Which AF point to use also depends, center AF point on most cams is more sensitive. I used to use center AF point almost all the time on my 10D. Basically focus, re-compose and shoot. Now a days, I am trying to use different AF point which is closer to the eye as I am able to get closer to the birds and with full-frame shots, I can not focus-recompose using the center AF point.
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Old May 17, 2006, 7:54 PM   #8
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which are blamed on lenses or the camera, when in fact they are simply operator error
Maybe peripatetic is referring again on that Sigma 10-20 issue ... :roll:I do not know why is to so hard to accept the fact that there are bad lenses out there, not just bad 'photographers'?

The method with a center point works fine most of the time. Unless your object is very close and, as peripatetic mentioned, you are using large aperture,the difference in the distance between the center and left AF point is not that great to affect the sharpness (we all know trigonometry?). I never had a single shot that was not sharp because of this 'method'. Everything also depends on what kind of lens we are using as well (wide, normal, 'tele').

Having more AF points is certainly welcome and for the best results AF point has to be selected manually. It all depends on the situation and the subject. For example taking picture of the person standing, where camera is low and rotated 90dgr (for reason of the special effect or cut) should be done by selecting leftmost or rightmost AF point.

Again for casual shooting, landscape and in most of the situation, using only center point AF is fine. For me, personally, rotating the dial or using 'joystick button' all the time is just unpractical. Again, there is no single rule what is the best for everyone.

The beauty of digital is exactly there to try every option and to check the results without (much of) cost! Assuming that we all know the basics ... and if we don't it is simple andfun enough to learn in couple of hours! Than comes the mastering!

Probably the most difficult pictures to take (if we are 'talking' of focus only) are pictures of the fast moving object. In that case rotating dial to select AF just doesn't work (for me again)!Especially when panning the camera and where Dynamic AF mode is used.But with little practice ...

Maybe next Canon release will have eye selectable AF points as Elan had. :idea:



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Old May 17, 2006, 10:28 PM   #9
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If you look at the AF points in 30D/20D viewfinder you can see that the points are arranged horizontalyat about 1/4 of the viewfinder. This is one (of two) test shots taken with only one (center) AF point used and focused on the top corner of the speaker. Lens was at 70mm and apperture at 4.5 which is not the largest but large enough for the test.

Then the lens was switched to manual. I still had AF point showing that other corner of the speaker (where leftmost AF point is) was in focus.The edge of the TV was in focus to. If I wanted my left corner of the speaker to be in the focus, I could still use centar AF point, recompose the picture and still have it focussed.

I suggest to anyone not accustomed to selecting AF points to try as many test shots with different settings. By practicing one will figure what works the best for him/her.

(for some reason, even though I had AF point lit in my viewfinder it doesn't show in Canon Browser, but that is not the point)

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Old May 18, 2006, 3:38 AM   #10
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Maybe peripatetic is referring again on that Sigma 10-20 issue ... :roll: I do not know why is to so hard to accept the fact that there are bad lenses out there, not just bad 'photographers'?
LOL, you see thousands of complaints on forums about bad lenses. Most of those are made by bad, or at least inexperienced, photographers and very few are ever backed up with pictures which can prove anything one way or another.

I'm not extrapolating from a single incident. Maybe that Sigma 10-20 is just cheap and nasty in general, but we've seen enough incidents (the majority IMO) where the equipment is blamed and it's the photographer that has the problem.

In this particular case it was always likely that it was the lens that was a problem, but being stubborn and ornery I wouldn't want to admit that. :-) But I do think it's a good idea to learn to do proper lens tests so that when you do get a bad one you can demonstrate it beyond any doubt. :blah:


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The method with a center point works fine most of the time. Unless your object is very close and, as peripatetic mentioned, you are using large aperture, the difference in the distance between the center and left AF point is not that great to affect the sharpness (we all know trigonometry?).
Really? Even if we do, and many don't, often it won't be on peoples' mind when taking photos, and there are many posts complaining about OOF pictures when using that method. Usually it's blamed on the lens.


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I never had a single shot that was not sharp because of this 'method'.
OK good for you, I have had many, but recommending a technique that can cause errors as a "this works best most of the time" is probably not optimal, because it depends entirely on the situation. For a lot of my pictures it would lead to an unacceptably high percentage of unsharp shots. Anyone who uses wide apertures, particularly with telephoto lenses needs to understand this. Many of my shots have very narrow DOF perhaps only a centimeter or two and that method would make the subject OOF.

I don't think you can say "use centre focus and recompose and don't worry about it", IMO "use centre focus and recompose and be careful" is much better advice.




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