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FORUMS Photography Talk by Genre General Photography Talk 
Thread started 07 Apr 2011 (Thursday) 22:37
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center AF vs 9-point AF

 
pbelarge
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Apr 11, 2011 09:07 |  #31

CaptivatedByBeauty wrote in post #12190696 (external link)
Wouldn't be it great if you could simply move the centre AF point around, and select the spot you want to use! And the little square would move exactly to show where the sensor was :) I don't know whether any camera manufacturer has implemented such a system.


Is not the focusing points of the 7D similar to this thought, with most of them being the crosshair type? So moving to an outer point will still be accurate?

If this is so, it would be one of the reasons I would move to the new iteration of the 5DII ...if they work on the AF of that new iteration.:cool:


just a few of my thoughts...
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tkerr
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Apr 11, 2011 09:22 as a reply to  @ post 12199376 |  #32

To recompose while on the move and maintain a focus point is easier said that done. There is already a risk of focusing error when you recompose a shot as it is, let alone when both you and the subject are moving. :rolleyes: Especially when using a larger aperture / Narrower DOF.
I wouldn't even think of attempting it unless the camera were on a tripod, and not while shooting a moving object. And then I would probably choose to manually focus anyways so the AF point doesn't matter then.

Choose the right AF Point and you don't have to worry about recomposing the shot.
Shot re-composition is IMHO Outdated and totally unnecessary with a modern day Digital SLR that has Multiple AF Points. Shot Recomposing is from the days of film cameras that could only focus on the center of the focus screen. On the other hand however, if you're shooting in low light then the center AF point might be your best, possibly only option. Again however, you would be using a tripod.


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soleful2001
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Apr 13, 2011 07:56 |  #33

I agree with tkerr. The autofocus point, at least on the 50D is quite quickly selected/changed when using the fantastic quick wheel on the back.

As for moving subjects, I like to use AI Servo mode. I tend to avoid AI Focus, as this does not seem to be effective.

that's my meager .02 worth.


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spinney
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Apr 13, 2011 08:58 as a reply to  @ soleful2001's post |  #34

when I shot with xxxd bodies it was center af focus recompose as it only has center cross type point.

Now I shoot xxd bodies with all af points cross type, I switch point selection to the joystick (way quicker than the wheel) and use the af point closest to where i want focus.

and now i have a xd body i am picking up friday and cannot wait to say good by to the inferior 9 point af system;)


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tkerr
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Apr 13, 2011 10:02 |  #35

soleful2001 wrote in post #12212711 (external link)
As for moving subjects, I like to use AI Servo mode. I tend to avoid AI Focus, as this does not seem to be effective.

When using AI Focus, once the camera detects motion it is supposed to switch to AI Servo Automatically. But I don't know how fast it is at doing it. Is it a micro-second a second or what?


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clark ­ becker
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Apr 13, 2011 10:22 |  #36

When shooting sports I would always use one of the outside focus points, because there was not enough time to recompose to make a pleasing composition. For portraits I would normally just use the center point, and for everyday use I would use the center point. Now I don’t use autofocus so I can compose where ever I want in the frame and still get good focus. I just shot a wedding with manual focus the whole time and there are much better pictures because I was not held down by the focus points.


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nathancarter
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Apr 13, 2011 11:59 |  #37

tonylong wrote in post #12190923 (external link)
One thing to bear in mind -- there is a difference between on-the-fly handheld shooting, like Tim mentions, and in which "acceptable sharpness" has a broader interpretation. and "critical demand" shooting in which you want to take strides to optimzize that critical sharpness in your technique. Not that we should ever be sloppy, and I still tend not to center-point focus and recompose, but I can't afford to be too picky when I'm shooting something on-the-run.

This is a good point. As an example, I shot some roller derby a few weeks ago, and for the majority of the time I was using center-point AF and AI Servo to focus the moving skaters. But in the brief times when the skaters were NOT moving, I would focus and recompose to get portrait-style photos, or full-length body shots. I didn't have time to switch AF points and focusing modes before they were rolling again. I suppose I could have switched the lens to manual focus and back again, but I'm not that good yet.

In more controlled situations - posed portraits or still life - then it's better to choose the most appropriate AF point, or if possible use manual focus. As alluded to above, in many situations when you focus-and-recompose, after you recompose your focal plane may be behind your original target. There's a thread around here somewhere that talks about it in depth, and gives diagrams to explain it better.

On a side note, in controlled situations, I love LiveView + 10x Zoom for manual focusing.

clark becker wrote in post #12213549 (external link)
Now I don’t use autofocus so I can compose where ever I want in the frame and still get good focus. I just shot a wedding with manual focus the whole time and there are much better pictures because I was not held down by the focus points.

How long did it take you to get confident and comfortable enough with your skills to pull this off? Any tips for a manual-focus amateur? (I guess we're getting off topic here.)


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clark ­ becker
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Apr 13, 2011 12:05 |  #38

I started out with manual focus cameras off the start. Then when I got auto focus camera, I never really got use to it. I always used it to zone focusing. Then I moved away from autofocus camera the beginning of this year. I still used the manual focus cameras through the time I had the autofocus cameras. It just takes time and confidence.

As for a tip. Practice, practice, practice. It will become second nature. It is faster for me to manual focus then to pick a autofocus point and then focus.


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Apr 13, 2011 17:58 |  #39

clark becker wrote in post #12214262 (external link)
I started out with manual focus cameras off the start. Then when I got auto focus camera, I never really got use to it. I always used it to zone focusing. Then I moved away from autofocus camera the beginning of this year. I still used the manual focus cameras through the time I had the autofocus cameras. It just takes time and confidence.

As for a tip. Practice, practice, practice. It will become second nature. It is faster for me to manual focus then to pick a autofocus point and then focus.

The big problem with depending on MF with our DSLRs is the inadequacy of our viewfinders when it comes to MF. Even with the full frame cameras, you really will get the best results with an add-on focusing screen.

Of course you can get results, and, if you use Live View you can zoom in and get great results, but both approaches tend to take some time, and to me I only have the time when I'm doing a thought out shoot of some kind. AF is my go-to mode most of the time.


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clark ­ becker
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Apr 13, 2011 23:19 |  #40

For the wedding that I shot I was an second shooter and I was using there 5d. It is easily the best Dslr I have used for mf but it still was not great.


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Apr 14, 2011 06:50 |  #41

tkerr wrote in post #12213413 (external link)
When using AI Focus, once the camera detects motion it is supposed to switch to AI Servo Automatically. But I don't know how fast it is at doing it. Is it a micro-second a second or what?

When using AI Focus mode, I find that my results are not as consistent. I do not get as many sharply focused images as I do with AI Servo.


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CaptivatedByBeauty
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Apr 14, 2011 16:00 |  #42

pbelarge wrote in post #12199407 (external link)
Is not the focusing points of the 7D similar to this thought, with most of them being the crosshair type? So moving to an outer point will still be accurate?

If this is so, it would be one of the reasons I would move to the new iteration of the 5DII ...if they work on the AF of that new iteration.:cool:

Sorry, I missed your reply!
The 60D also has all cross type sensors, but the centre one appears to be more sensitive and is where the black square is. I don't know whether the 7D centre sensor is the same as all the others.
I assume the reason for many sensors is the idea that the camera will find the nearest object if all sensors are selected. But in practice I find most of the time no sensor is on the nearest object I'm wanting to focus on, so unless the number of sensors is enough to avoid missing objects, that method seems of little use.
Being able to move one sensitive and well-defined sensor to just the right place seems to me like a useful idea. Maybe done like a laptop mouse pad?

One slight complication is the effects of the lens. Nearer the edge the image is likely to be less will defined, and so focusing will be less easy/accurate. Maybe that's why none of the AF sensors are very close to the edges? This might explain why the outer AF sensors are inherently less good than the centre one, as the centre of the image is usually the best quality.

Using LiveView and 10x magnification, and with the tiling LCD on the 60D, is a very good method when wanting to avoid recomposing, for static scenes. Also very good for checking whether the AF has really got it right.


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Apr 18, 2011 13:34 |  #43

tkerr wrote in post #12189321 (external link)
I know focusing on the eye isn't the right place to aim the AF point

Sorry for jumping on on this thread, but where should the AF point be if not on an eye? Seems like everything I've read recommends having it on an eye?


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Apr 18, 2011 14:39 |  #44

deronsizemore wrote in post #12246454 (external link)
Sorry for jumping on on this thread, but where should the AF point be if not on an eye? Seems like everything I've read recommends having it on an eye?

For portraits it is the right place to focus. Focus on the eye nearest the camera with a shallow DOF.
But It's not always the right place in a similar situation to what I was shooting. Nevertheless it's the eyes you want in focus because that's one of the first things your attention is drawn to when you look at the photo. Since she was turned away slightly getting both eyes in focus wasn't really an option at that distance and DOF, otherwise I probably would have tried harder to aim between to get them both in focus along with as much of her face as possible.


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deronsizemore
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Apr 18, 2011 15:16 |  #45

tkerr wrote in post #12246918 (external link)
For portraits it is the right place to focus. Focus on the eye nearest the camera with a shallow DOF.
But It's not always the right place in a similar situation to what I was shooting. Nevertheless it's the eyes you want in focus because that's one of the first things your attention is drawn to when you look at the photo. Since she was turned away slightly getting both eyes in focus wasn't really an option at that distance and DOF, otherwise I probably would have tried harder to aim between to get them both in focus along with as much of her face as possible.

I see. Thanks for the clarification.


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center AF vs 9-point AF
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