AF-Area Modes; 9-points vs single-point

[ChillOne]

Question to all ... I am using the AF-ON focus technique and mainly shoot people -- portraits, almost all the time, stationary in movement. I am currently shooting with AF-S and single-point AF. Is there a reason why I would not want to use single-point AF in this situation? I have read that some here recommend the 9-point with AF-C. Thoughts/comments?

 

[Mako2011]

Question to all ... I am using the AF-ON focus technique and mainly shoot people -- portraits, almost all the time, stationary in movement. I am currently shooting with AF-S and single-point AF. Is there a reason why I would not want to use single-point AF in this situation? I have read that some here recommend the 9-point with AF-C. Thoughts/comments?

Using AF-ON with AF-S negates many of the advantages of the AF-ON technique as focus stops as soon as focus is confirmed.

http://forums.dpreview.com/forums/read.asp?forum=1034&message=40652306

AF-Area mode single may be fine and is subject dependent but AF-Area mode "9pt" may help even when the subjects moves just a tiny bit or the target is lacking solid contrast.

AF-Area mode "9pt" is not really tracking the subject like 3D-tracking does. It's more like using the surrounding sensors to detect small movement of the subject within the range of the primary AF sensor. It also helps provide more contrast information to allow the primary sensor to get lock and maintain it. Once the subject moves outside the area covered by the primary sensor....focus will shift to another target in the primary sensors area if the scene contains many subjects/targets. If you map out the sensor coverage of all 39, I think you'll find that "track" is not quite the right word in describing how 9pt functions. When the target is a simple one on a uniform background (large bird and blue sky) it does seem to work that way. In the case of a complicated subject like soccer players with a busy background...It helps you keep lock while panning but will not actually track the subject. Said another way, the dynamic AF-Area modes are very dynamic in how they treat a subject and very greatly with the type of scene you have.

Also

"9pt" is like focus "enhancement". In 9pt the algorithms seem to understand or be geared towards precision. While in AF-Area mode 39pt, when the background is uniform you do get a more tracking like response that only stops when the original target is complicated by contrast or a more "suitable" subject falls under the original primary AF-sensor. 21pt is simply more of a compromise between the two. In that way, the whole system really is dynamic, much the same way that matrix metering is dynamic.

Good Luck

 

[ChillOne]

Thanks Mako! So, from the technical description you've provided -- even when shooting a stationary subject (posed/portrait), I should achieve better focus and sharpness with my D7000 using AF-C and 9-point AF area versus AF-S and single-point. Is that correct?

 

[Ray Soares]

The problem is that even so called stationary objects posing, are NOT really stationary, as they breath and move as you also do when handhelding.

If you shoot at f1.4 to f2.8 ANY small movement will kill your critical focus, so AFC with small DOF is a must IMO.

If you shoot only at f8, or landscapes, or architecture with a tripod you may use AFS with no penalty.
Best
--
Ray Soares

See my pictures at http://www.pbase.com/raysoares

 

[Mako2011]

The problem is that even so called stationary objects posing, are NOT really stationary, as they breath and move as you also do when handhelding.

If you shoot at f1.4 to f2.8 ANY small movement will kill your critical focus, so AFC with small DOF is a must IMO.

If you shoot only at f8, or landscapes, or architecture with a tripod you may use AFS with no penalty.
Best

Mr Soares said it well. AF-C, IMO, is for dynamic situations and many situations are far more dynamic than we give credit. Practicing shot discipline with AF-S and AF-C will lead to better results. Knowing what AF-Area mode best fits the situation is important. Try each for a month then sit back and evaluate what worked best and when. You have a very capable camera, explore it. Good Luck.

 

[winparkman]

Yeh, but shooting at f/4+, I don't think its an advantage to be in AFC. In fact, once I have achieved focus on, say, an eye, I don't want the focus to shift to anything else. Moving subjects, like a toddler, OK but for an older child or adult, I prefer to select exactly where I want the focus.

The problem is that even so called stationary objects posing, are NOT really stationary, as they breath and move as you also do when handhelding.

If you shoot at f1.4 to f2.8 ANY small movement will kill your critical focus, so AFC with small DOF is a must IMO.

If you shoot only at f8, or landscapes, or architecture with a tripod you may use AFS with no penalty.
Best

Mr Soares said it well. AF-C, IMO, is for dynamic situations and many situations are far more dynamic than we give credit. Practicing shot discipline with AF-S and AF-C will lead to better results. Knowing what AF-Area mode best fits the situation is important. Try each for a month then sit back and evaluate what worked best and when. You have a very capable camera, explore it. Good Luck.

--
OK, not so purely a hobby.

 

[Mako2011]

Yeh, but shooting at f/4+, I don't think its an advantage to be in AFC. In fact, once I have achieved focus on, say, an eye, I don't want the focus to shift to anything else. Moving subjects, like a toddler, OK but for an older child or adult, I prefer to select exactly where I want the focus.

I see what your saying but even at f4 in AF-S once you focus on the eye, you're locked to the focus plane regardless of what the subject does before you fully engage the shutter. With even an older subject, AF-C allows you to maintain focus on the eye regardless of what happens....but it does require a bit of shot discipline. Once you get focus with AF-S, by definition, you're now living in the past

 

[winparkman]

I'll give it a try although I am skeptical.

Yeh, but shooting at f/4+, I don't think its an advantage to be in AFC. In fact, once I have achieved focus on, say, an eye, I don't want the focus to shift to anything else. Moving subjects, like a toddler, OK but for an older child or adult, I prefer to select exactly where I want the focus.

I see what your saying but even at f4 in AF-S once you focus on the eye, you're locked to the focus plane regardless of what the subject does before you fully engage the shutter. With even an older subject, AF-C allows you to maintain focus on the eye regardless of what happens....but it does require a bit of shot discipline. Once you get focus with AF-S, by definition, you're now living in the past

--
OK, not so purely a hobby.

 

[hamton]

I tend to shoot mostly portrait too and I prefer AF-C with single point. I tried 9 points but sometimes the camera would pick one of the other 8 points to focus. Since most of my photos are pretty much stills, I use single. If there is motion like a kid running, I would switch to 9.

 

[Mako2011]

I'll give it a try although I am skeptical.

That's the trick...just giving it an honest try. In my quest to master the D7000 focus (still ongoing) I started out just as I had with my D70. AF-S and single point. The results just weren't what I expected so I started searching for the answer to why. When I started, I was shooting the vast majority of my shots hand held and low ISO in aperture priority. That naturally lead to tight DOF and a dynamic focus plane regards the subject. I also learned the FOV of the actual focus arrays was not the same as the depicted focus box in the viewfinder. I started paying close attention to what was happening regard focus in the view finder. AF-C made it easier too monitor the relationship. AF-Area mode "9pt" (menu a3 "off") was also suggested. I decided to stick with that for awhile. The combination put focus more in my hands as I now had to "pay attention". In a short time I got very used to the control it afforded. I now find AF-S to be like trying to walk with a requirement to re-tie my shoes between each step.

I now normally shoot in AF-C, CH, and swap between AF-ON and normal depending on the situation. "9pt" most of the time but I do still use "single" in certain very cluttered scenes. Looking forward to the spring to give my dog a workout with "3-D"

Give it a fair test drive. Always easy to return to the other way and you'll get a little more familiar with your camera regardless and that's never a bad thing. Come up with a suggestion that will improve my results and I'll happily give it a run. I like seeing what's around the corner. Good Luck

Yeh, but shooting at f/4+, I don't think its an advantage to be in AFC. In fact, once I have achieved focus on, say, an eye, I don't want the focus to shift to anything else. Moving subjects, like a toddler, OK but for an older child or adult, I prefer to select exactly where I want the focus.

I see what your saying but even at f4 in AF-S once you focus on the eye, you're locked to the focus plane regardless of what the subject does before you fully engage the shutter. With even an older subject, AF-C allows you to maintain focus on the eye regardless of what happens....but it does require a bit of shot discipline. Once you get focus with AF-S, by definition, you're now living in the past

--
OK, not so purely a hobby.

 

[JCB123]

In 9 point dynamic area mode the camera does not choose the initial focus point - You do. It will then maintain focus on your chosen part of the scene and will only mave to another point if the camera or subject move. So if you have chosen a focus point over an eye the camera will maintain focus on that eye unless it moves outside of the area covered by the 9 points.

In single point mode if the camera or subject moves such that the single ponit is no longer on the eye the camera (in AF-C) will attempt to focus on whatever is now under your chosen sensor.

Using single point you would be better to use AF-S (but read Ray Soares post above)

In AF-C mode you are more likely to keep your focus on the eye using 9 point dynamic area (or one of the other dynamic area modes if there is more subject motion)

 

[ChillOne]

Thank you all for the insightful replies! I, like Mako, am in the neverending quest for the best D7000 technical focus set-up! I will continue to test and play around, but I do appreciate all the input!

• Chill

 

[Mollysnoot2]

In 9 point dynamic area mode the camera does not choose the initial focus point - You do. It will then maintain focus on your chosen part of the scene and will only mave to another point if the camera or subject move. So if you have chosen a focus point over an eye the camera will maintain focus on that eye unless it moves outside of the area covered by the 9 points.

From my experience, this isn't always the case: in 9-point dynamic the camera can change the initial focus point if it detects stronger contrast under one of the surrounding focus points. This was a bit of a surprise to me, as I'd believed that it wouldn't do this.

I first noticed this when taking some portrait shots using the camera hand-held and in AF-C 9-point dynamic. I was getting some great focus locks with no issue, then I moved slightly and changed focal length. Focused again on the subject's eye, waited for it to confirm focus, then clicked away... And the eye I had my initially selected focus point over wasn't in focus. I put it down to simple Af error and tried again - same thing. After the third attempt, I pulled up the display on the LCD that shows where the focus point locked, and it had decided to move my chosen focus point to one of the outer ones, preferring the (apparently) stronger contrast of the subject's nose. I switched to single-point, and perfect focus was immediately achieved on the eye that I'd been keeping my chosen focus point over all along (subject was not moving around).

I've since done more controlled testing of this behaviour and it does choose the focus point for you in certain circumstances. You can test this yourself: set up the camera in AF-C 9-point and select a focus point (I'd chose the middle one to keep things simple by using the cross-point sensors); point it at a reasonably sized featureless area (say an interior wall) where the AF has no chance of getting a lock, and all nine points are well clear of any contrast. Keep the focus active (button down) and pan very slowly toward an area of contrast (a picture on the wall for example), keeping a close watch on when focus is achieved - as soon as it is , stop and take a shot (don't keep panning). I'd advise using a tripod to help with controlling the panning smoothly and slowly, and then locking it as soon as you get focus so the camera doesn’t move and skew the results (but maybe you have great handheld panning technique!). Let's say the picture was to the left-hand side of the selected AF point and you slowly panned left toward it: you should find that the camera has switched from your chosen point to the one of the ones to the left of it; I used to expect that it wouldn't do that initially - that it would wait until my chosen (middle) AF point found contrast, and then move to another point if I subsequently moved the camera so that the selected AF point wasn't covering the subject. Hope you can see the distinction here – obviously all the dynamic modes can switch AF points depending on the situation, but I didn’t think they’d do so before the initially chosen point had even got a lock.

9-point works just great most of the time, but I believe, mainly due to the behaviour I describe above, that it can sometimes be better to switch to single-point in certain situations where the 9-points cover a variety of potential 'targets', otherwise it might just choose a different area to focus on than you'd wanted. I also wonder if this is sometimes the cause of people's frustration when they don't get the results they expected. Of course, that's why we have so many choices when it comes to auto-focus: different tools for different tasks.

M

 

[Mako2011]

In 9 point dynamic area mode the camera does not choose the initial focus point - You do. It will then maintain focus on your chosen part of the scene and will only mave to another point if the camera or subject move. So if you have chosen a focus point over an eye the camera will maintain focus on that eye unless it moves outside of the area covered by the 9 points.

From my experience, this isn't always the case: in 9-point dynamic the camera can change the initial focus point if it detects stronger contrast under one of the surrounding focus points. This was a bit of a surprise to me, as I'd believed that it wouldn't do this.

I first noticed this when taking some portrait shots using the camera hand-held and in AF-C 9-point dynamic. I was getting some great focus locks with no issue, then I moved slightly and changed focal length. Focused again on the subject's eye, waited for it to confirm focus, then clicked away... And the eye I had my initially selected focus point over wasn't in focus. I put it down to simple Af error and tried again - same thing. After the third attempt, I pulled up the display on the LCD that shows where the focus point locked, and it had decided to move my chosen focus point to one of the outer ones, preferring the (apparently) stronger contrast of the subject's nose. I switched to single-point, and perfect focus was immediately achieved on the eye that I'd been keeping my chosen focus point over all along (subject was not moving around).

I've since done more controlled testing of this behaviour and it does choose the focus point for you in certain circumstances. You can test this yourself: set up the camera in AF-C 9-point and select a focus point (I'd chose the middle one to keep things simple by using the cross-point sensors); point it at a reasonably sized featureless area (say an interior wall) where the AF has no chance of getting a lock, and all nine points are well clear of any contrast. Keep the focus active (button down) and pan very slowly toward an area of contrast (a picture on the wall for example), keeping a close watch on when focus is achieved - as soon as it is , stop and take a shot (don't keep panning). I'd advise using a tripod to help with controlling the panning smoothly and slowly, and then locking it as soon as you get focus so the camera doesn’t move and skew the results (but maybe you have great handheld panning technique!). Let's say the picture was to the left-hand side of the selected AF point and you slowly panned left toward it: you should find that the camera has switched from your chosen point to the one of the ones to the left of it; I used to expect that it wouldn't do that initially - that it would wait until my chosen (middle) AF point found contrast, and then move to another point if I subsequently moved the camera so that the selected AF point wasn't covering the subject. Hope you can see the distinction here – obviously all the dynamic modes can switch AF points depending on the situation, but I didn’t think they’d do so before the initially chosen point had even got a lock.

9-point works just great most of the time, but I believe, mainly due to the behaviour I describe above, that it can sometimes be better to switch to single-point in certain situations where the 9-points cover a variety of potential 'targets', otherwise it might just choose a different area to focus on than you'd wanted. I also wonder if this is sometimes the cause of people's frustration when they don't get the results they expected. Of course, that's why we have so many choices when it comes to auto-focus: different tools for different tasks.

M

Confirmed. I tested and you are right. One caveat though. There has to be no contrast for the primary sensor to lock onto or the focus quickly reverts back to the primary sensor you have selected. Said another way...If there is no contrast for the primary sensor to use, one of the outlying sensors may revert to primary temporarily (preference will be in the direction of movement). As soon as contrast for lock can be found under the FOV of the user selected sensor, it will revert back to being primary.

Thanks for pointing this out Mollysnoot2.....well done.

 

[Jim Holtz]

Confirmed. I tested and you are right. One caveat though. There has to be no contrast for the primary sensor to lock onto or the focus quickly reverts back to the primary sensor you have selected. Said another way...If there is no contrast for the primary sensor to use, one of the outlying sensors may revert to primary temporarily (preference will be in the direction of movement). As soon as contrast for lock can be found under the FOV of the user selected sensor, it will revert back to being primary.

Thanks for pointing this out Mollysnoot2.....well done.

Hi Mako2011,

I usually use the lock switch on the back to lock the focus point to the center unless I want to use one of the others. Won't the lock switch keep the focus point from automatically moving?

Thanks!

Jim

 

[Mollysnoot2]

Confirmed. I tested and you are right. One caveat though. There has to be no contrast for the primary sensor to lock onto or the focus quickly reverts back to the primary sensor you have selected. Said another way...If there is no contrast for the primary sensor to use, one of the outlying sensors may revert to primary temporarily (preference will be in the direction of movement). As soon as contrast for lock can be found under the FOV of the user selected sensor, it will revert back to being primary.

Thanks for pointing this out Mollysnoot2.....well done.

Quite welcome Mako, pleased to pass on some information on the focusing system to you, having gained some much insight on the subject from your posts! Your mapping of the focus points recently was especially helpful to me, and confirmed once and for all what I'd suspected for a while now: Hogan got it wrong in his user guide!

I largely agree with what you're saying about the primary focus point, but I have managed to get it to 'ignore' what appears to be sufficient contrast under the primary point on some rare occasions where it has instead deviated to one of the outer ones. My portrait session example was one such occasion: there was plenty of contrast for it to lock onto and every other shot I'd taken under the same lighting had been perfectly focused. I tested this further and it happened again in a different situation: Had the camera on a sturdy tripod with the 105 2.8 macro lens mounted, and pointed it at a TV remote with the centre point selected and aimed at the most prominent button on the remote. I was close up to the subject and therefore the focus point had ample coverage to get a lock. However, it instead chose to lock onto one of the other buttons lower down - this happened consistently each time I took a shot. Switched to single-point, and it instantly locked onto my initially chosen button with no problems, and got focus dead-on, confirming that there certainly was enough contrast under the focus point I'd selected. Camera didn't move during this test, and the lighting didn't change.

So it seems that even if there is enough contrast under the selected sensor, if there's even better contrast under another one, it might just opt to use that instead on rare occasions. The message I got was, if 9-point seems to be misbehaving, switch to single-point!

(I know, taking photos of remote controls! This isn't something I tend to do on a regular basis, I was just looking for something to test with!)

M

 

[Mako2011]

Confirmed. I tested and you are right. One caveat though. There has to be no contrast for the primary sensor to lock onto or the focus quickly reverts back to the primary sensor you have selected. Said another way...If there is no contrast for the primary sensor to use, one of the outlying sensors may revert to primary temporarily (preference will be in the direction of movement). As soon as contrast for lock can be found under the FOV of the user selected sensor, it will revert back to being primary.

Thanks for pointing this out Mollysnoot2.....well done.

Quite welcome Mako, pleased to pass on some information on the focusing system to you, having gained some much insight on the subject from your posts! Your mapping of the focus points recently was especially helpful to me, and confirmed once and for all what I'd suspected for a while now: Hogan got it wrong in his user guide!

I largely agree with what you're saying about the primary focus point, but I have managed to get it to 'ignore' what appears to be sufficient contrast under the primary point on some rare occasions where it has instead deviated to one of the outer ones. My portrait session example was one such occasion: there was plenty of contrast for it to lock onto and every other shot I'd taken under the same lighting had been perfectly focused. I tested this further and it happened again in a different situation: Had the camera on a sturdy tripod with the 105 2.8 macro lens mounted, and pointed it at a TV remote with the centre point selected and aimed at the most prominent button on the remote. I was close up to the subject and therefore the focus point had ample coverage to get a lock. However, it instead chose to lock onto one of the other buttons lower down - this happened consistently each time I took a shot. Switched to single-point, and it instantly locked onto my initially chosen button with no problems, and got focus dead-on, confirming that there certainly was enough contrast under the focus point I'd selected. Camera didn't move during this test, and the lighting didn't change.

So it seems that even if there is enough contrast under the selected sensor, if there's even better contrast under another one, it might just opt to use that instead on rare occasions. The message I got was, if 9-point seems to be misbehaving, switch to single-point!

(I know, taking photos of remote controls! This isn't something I tend to do on a regular basis, I was just looking for something to test with!)

M

I agree with you and concur that there are times when you need to change AF-Area modes for optimal results. Never get "locked" into one technique or setting. Don't forget also that the AF-Sensors are "seeing" in different wavelength than we do so just something to ponder.

 

[Mako2011]

Confirmed. I tested and you are right. One caveat though. There has to be no contrast for the primary sensor to lock onto or the focus quickly reverts back to the primary sensor you have selected. Said another way...If there is no contrast for the primary sensor to use, one of the outlying sensors may revert to primary temporarily (preference will be in the direction of movement). As soon as contrast for lock can be found under the FOV of the user selected sensor, it will revert back to being primary.

Thanks for pointing this out Mollysnoot2.....well done.

Hi Mako2011,

I usually use the lock switch on the back to lock the focus point to the center unless I want to use one of the others. Won't the lock switch keep the focus point from automatically moving?

Thanks!

Jim

Jim, I just tested. No, the lock switch will not keep the AF sensor selected as primary. It may still change in rare cases as Mollysnoot2 has showed.

 

[plaiditude]

This explains the trouble I was having a couple of months ago which mostly went away once I changed from 9pt to single point for my family photography shoots. I also changed from af-on back to the shutter button and from af-c to af-a. The number of my keepers went up dramatically. Technically it sounded as if my older settings should have worked better for what I was shooting, but I started to wonder if the 9pt was causing it to focus somewhere else than I wanted. It appears my intuition was at least partly right. Thanks!
--
http://www.anthonymarkphotography.net

 

[Jim Holtz]

I usually use the lock switch on the back to lock the focus point to the center unless I want to use one of the others. Won't the lock switch keep the focus point from automatically moving?

Thanks!

Jim

Jim, I just tested. No, the lock switch will not keep the AF sensor selected as primary. It may still change in rare cases as Mollysnoot2 has showed.

Hi Mako,

Thank you for the VERY quick test and response. Your answer is making me wonder if I wouldn't be better off using a single focus point with AF-C rather than 9 point since it's rare that I photograph a moving object.

Can you make any recommendations about single point?

Thanks for your help!

Jim