AF Area Mode
- Thread starter AndyRB
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The manuals (D3100 page 58, under AF-Area mode) says about Single Point AF : "Use for stationary subjects".
The multiple points are for various degrees of motion (it says there).
(my words): The advantage of single point is that we select the focus point. On multi-point, the camera picks one.
The multiple points are for various degrees of motion (it says there).
(my words): The advantage of single point is that we select the focus point. On multi-point, the camera picks one.
Horoscope Fish
Senior Member
You might want to read this Autofocus Explained. It gives a much deeper, clearer, explanation of the the different AF-Modes than the manual does.
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I was just going to post the doc HF just posted. Its really good write up. I still like to re-read it.
On single point, we pick the one and only. On dynamic, we pick a starting point and the camera can do some tracking from there if the subject moves AND you are using af-c (continuous servo). On a simple non-moving subject, you should get the same result from single and dynamic.
On single point, we pick the one and only. On dynamic, we pick a starting point and the camera can do some tracking from there if the subject moves AND you are using af-c (continuous servo). On a simple non-moving subject, you should get the same result from single and dynamic.
I personally never use Dynamic mode. I primarily use Single Point because I want to control where the focus point is at all times. I have lost several bird in flight shots using Dynamic.
We do. when we're in single point.
Thanks for the article, it was very helpful. Although i was a little confused by this paragraph
"For AFC,examples of using Single Point are track and field, motor sports, and birds at rest. I use birds at rest because a bird
at rest is likely to have some motion."
I would have assumed you would use dynamic for track and field and motor sports.
Another user of single point,including birds in flight for the same reason as Mike D90,this is what annoys me about the D5100 you cant lock it.
I was just going to ask where the lock is...
When tracking a fast moving object such as a runner or race car, or flying bird even, you will usually be using a high shutter speed to stop movement. This means you may also need to use a wider aperture so you can achieve the necessary exposure. When you do that you have narrow depth of field. Since you have narrow depth of field you need to assure that you focus exactly where you need focus, the eyes for example or face, or your image will be out of focus in the key areas. Using single point area with AF-C allows you to pinpoint the focus area and it won't suddenly jump to another area of movement, such as another runners arms or legs, and you miss your focus.
That is why I don't use dynamic tracking with moving/flying birds. Any movement of the background, such as tree limbs or other birds in the air, will cause auto focus to move from the subject I want in focus. Focus works by comparing contrast. Birds that contrast against a wooded background can easily be lost to the difference in contrast of the wooded branches that may also be moving in the wind.
You may be missing out on a very good thing then.
That is not how the system is designed.I do use single point non-dynamic focus maybe 99% of time, preferring to chose what I am focused on (stationary subjects, landscapes, portraits, macro, etc). I don't do sports, but there are times the action is just too fast for me, and then the many-points dynamic really comes through, letting the camera have it to run with it, to try to find something to focus on. This action below was quite fast, more so since it was so close (first one is just cropped, it is same distance as the second - but the birds were just a flash).
Note there different methods that cameras use to auto focus. The two used in DSLR are Phase and Contrast. The DSLR is predominately Phase Shift, using the viewfinder. But Contrast focusing is done by the mirrorless systems (including compacts and DSLR Live View), when all there is to work with is the image pixels (no actual focus system present). But when the DSLR viewfinder system is instead enabled, its complex dedicated phase shift system just for focus has substantial advantage - (esp speed - but it is a bit complex, see Wikipedia ).
The above is dynamic Phase using the viewfinder - I very seriously doubt Live View Contrast could hack this.
These are extremely different systems. D3100 spec page says:
Auto Focus is Phase on up to 11 focus points,
and says Live View is Contrast, anywhere in the frame (there are just pixels to look at, no focus points).
The Nikon manuals say use Single Point for stationary subjects. Seems easy to understand. Then dynamic has a few stages of more and more points to try to sense how the motion is moving. Slower motion only needs a fewer smaller group, faster action needs more and wider points to hunt in (and it has a wide choice to choose from). I think the manual says it very clearly.
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You may be missing out on a very good thing then.
I do use single point non-dynamic focus maybe 99% of time, preferring to chose what I am focused on (stationary subjects, landscapes, portraits, macro, etc). I don't do sports, but there are times the action is just too fast for me, and then the many-points dynamic really comes through, letting the camera have it to run with it, to try to find something to focus on. This action below was quite fast, more so since it was so close (first one is just cropped, it is same distance as the second - but the birds were just a flash).
Note there different methods that cameras use to auto focus. The two used in DSLR are Phase and Contrast. The DSLR is predominately Phase Shift, using the viewfinder. But Contrast focusing is done by the mirrorless systems (including compacts and DSLR Live View), when all there is to work with is the image pixels (no actual focus system present). But when the DSLR viewfinder system is instead enabled, its complex dedicated phase shift system just for focus has substantial advantage - (esp speed - but it is a bit complex, see Wikipedia ).
The above is dynamic Phase using the viewfinder - I very seriously doubt Live View Contrast could hack this.
These are extremely different systems. D3100 spec page says:
Auto Focus is Phase on up to 11 focus points,
and says Live View is Contrast, anywhere in the frame (there are just pixels to look at, no focus points).
The Nikon manuals say use Single Point for stationary subjects. Seems easy to understand. Then dynamic has a few stages of more and more points to try to sense how the motion is moving. Slower motion only needs a fewer smaller group, faster action needs more and wider points to hunt in (and it has a wide choice to choose from). I think the manual says it very clearly.
I have just never been successful with it then. Even with a single subject, using Dynamic tracking area, focus points hunted and jumped all over the place. Maybe I will work with it some more and see what I get.
I just spent some time reading this and must admit that even though it is a "simplified" explanation I still found it pretty confusing.
However it is extremely interesting (even for a D5100 owner like myself) and I find the exercises at the end interesting. Definitely worth trying. Do them often enough and they are committed to memory just as military drills (such as weapon stripping and assembly) can be done with eyes closed even years (too many) later.
Thanks for posting.
I need to back track here a bit and state that I was giving information based on the D90 AF system, which is the Multi-Cam 1000 AF system. It's 3D tracking mode is for use on stationary subjects when you want to focus and recompose and keep focus on your subjects selected area. On the D300 AF system, the 3D tracking was for actually tracking moving objects.
The Dynamic AF mode, on the D90 Multi-Cam 1000 system, is for tracking moving objects. So, I need to use this mode a bit and see what I get. I hope I have not given out bad information here and if I have I apologize.
The Dynamic AF mode, on the D90 Multi-Cam 1000 system, is for tracking moving objects. So, I need to use this mode a bit and see what I get. I hope I have not given out bad information here and if I have I apologize.
I am puzzled by the distinctions too. This is really not my subject, I can just read the manual.
D90 and D3100 both say they have the Multi-CAM 1000 module, Phase, with 11 focus points.
Both say their Live View is Contrast, anywhere in frame.
Both seem to use 3D as a synonym for 11 points "3D tracking (11 points)". Both allows user to select initial focus point.
Both have Auto Area, where camera detects subject and selects initial focus point.
D300 does make a distinction. The D300S has the same choices, but it adds a lot more words (D800 says exact same words):
Single point focus - use for stationary subjects
9 points - for subjects moving predictably - runners or race cars on a track
21 points - unpredictable motion - football players
51 points - moving quickly, not easily framed - birds
51 points 3D - subjects moving erratically side to side - tennis players. Adds if they leave the frame, remove finger from shutter.
No clue what 3D does.
Also has Auto Area, where cameras selects subject and initial focus point.
More points gives camera much more choice to find a subject.
Fewer points obviously let us confine it closer to the subject. Which must be good, because it is provided.
D90 and D3100 both say they have the Multi-CAM 1000 module, Phase, with 11 focus points.
Both say their Live View is Contrast, anywhere in frame.
Both seem to use 3D as a synonym for 11 points "3D tracking (11 points)". Both allows user to select initial focus point.
Both have Auto Area, where camera detects subject and selects initial focus point.
D300 does make a distinction. The D300S has the same choices, but it adds a lot more words (D800 says exact same words):
Single point focus - use for stationary subjects
9 points - for subjects moving predictably - runners or race cars on a track
21 points - unpredictable motion - football players
51 points - moving quickly, not easily framed - birds
51 points 3D - subjects moving erratically side to side - tennis players. Adds if they leave the frame, remove finger from shutter.
No clue what 3D does.
Also has Auto Area, where cameras selects subject and initial focus point.
More points gives camera much more choice to find a subject.
Fewer points obviously let us confine it closer to the subject. Which must be good, because it is provided.
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The articles I read on the 3D tracking, with the Multi-Cam 1000 system, is that it adds the "distance" data to the AF system and can adjust focus if camera to subject distance changes after initial focus/compose was established. Apparently this can happen when using "focus and recompose".
As to Dynamic AF mode, I tried that today and it works just fine. Actually I got better focus, more consistent focus, on my flying bird subject than with Single Point.
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Horoscope Fish
Senior Member
Example of 3D Tracking: Picture it -- There you are on the romantic plains of the African Serengeti! You survey a gorgeous... Nay... Ferocious man-eating tiger lounging in the mid-afternoon sunshine. You've composed your shot from a safe distance but, in so doing, have managed (however inexplicably) to *severely* piss off said ferocious, man-eating tiger which is now sprinting towards you at full speed, fangs bared for the inevitable kill. Anticipating just such circumstances, however, you have wisely selected to employ Auto-focus *with* Nikon-patented 3D-Tracking technology!
This ensures Shere Khan, even as he closes the distance between you in mere fractions of a second, changing the focal point as he does so, stays in clear focus as you snap away. Oh yes, great white hunter... Rest easy in knowing the last photos you will ever take while bound in this mortal coil will be clear and (almost) as razor-sharp as pretty kitty's glinting incisors! Give ye thanks to Nikon's patented 3D Tracking which maintains focus on natures perfect killing machine even as it's distance decreases from casual-viewing meters, to throat-ripping centimeters!
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