Tuesday, October 9, 2012

Nikon D600 autofocus: speed, accuracy, low light, and clustering

10/11/12 UPDATE: Added Nikon D3 shots for comparison
10/22/12 UPDATE: Added shots showing AF speed

Nikon D600 + Sigma 50 1.4 @ f/2.0
Because my subjects often move, one of the most critical components of any camera for me is its autofocus system.  What's the use of a very high resolution sensor with extremely low noise if the shot I capture is blurry - not because of subject movement but because the subject is out of focus?

In this post I will discuss my experience regarding the Nikon D600's autofocus speed and accuracy.  I will also discuss the clustering of autofocus points.

(And even though you may not be in the market for a D600, you may be interested in reading about a couple of alternatives to focus-and-recompose.)


SPEED AND ACCURACY

I tested the Nikon D600's autofocus speed and accuracy using a Sigma 50 1.4.  If you've shot with a 50mm lens at f/1.4 you know the depth of field is razor thin, especially at the usual shooting distances of a full frame camera, i.e., closer than on a crop sensor when maintaining the subject size in relation to the frame.  I tried shooting at very wide apertures, such as f/2 and even f/1.4.

(Before testing the Sigma 50 1.4, I fine-tuned the AF using the moire method described here.)

When I shoot a subject that can move, I usually use AF-C even if the subject is not moving at that particular moment.  I also prefer to set my AF-C to focus priority instead of release priority, meaning the camera will do its best to get accurate focus even if it means that it will take longer to acquire focus.

a.  Subject not moving much.
With this method, I took a few snaps to test the D600's AF.  I found that the D600's AF was fast and accurate enough to capture shots when the subject is not moving much.  This one was at f/1.4 with the AF point on my son's near eye:
The focus was spot-on (click on it to get a high-res version).

This other one was only at f/2.0 but with my son so close to the camera, the DOF was very thin.  The AF point here was on the near eye (his left, camera right).
To me it looks a little bit behind - the far eye seems to be more in focus, but the focus was more than acceptable to me.

Here is a series of shots taken in bursts to give you an idea of the consistency of the autofocus.  These were at f/1.4.  The AF point on these were approximately on the near eye though because of subject movement, it sometimes got outside of that.

Here are the shots.  (Please excuse the garish colors on some of them.  It seems that Picasa is doing something automatically to some or all of the shots.)








As you can see, a few of the shots are not in focus, but the others have acceptable or even spot-on focus.  Considering that these were at f/1.4, I like the Nikon D600's AF performance.

LOW LIGHT
The D600's autofocus is designed to work in low light environments -- as low as -1 exposure value (explained here).  Last week I tried focusing on a subject lit only by a bedside lamp (the EV was around 4), and the camera focused accurately and with no hunting even though I was using a relatively slow lens with an aperture of f/4.5.  A couple of days ago, I was able to focus in an environment that required an exposure of 25600 ISO, f/2.8, 1/60 which is an EV of 1.  Again the camera focused quickly and accurately, with no hunting at all (I was using the Nikkor 24-70 2.8G).  I will post that sample soon.

CLUSTERING OF AF POINTS
The shots above were taken while the AF point was more or less where it needed to be.  The problem for the Nikon D600 is that its 39 autofocus points are clustered tightly in the middle, occupying only about 1/9th of the total frame area.  Essentially it appears that the AF points were carried over from the D7000 with no change, except that now the frame area is twice as large, so the AF coverage is much smaller:
Inline image 1
Nikon D600's 39 AF points*
*From the viewfinder display shown on the Nikon D600 product manual. I removed the surrounding grid lines.
On the other hand, the clustering of AF points is an issue with other Nikon full frame cameras as well, albeit to a lesser extent:

Inline image 2
The Nikon D800 AF points*
*From the product manual, also edited to remove the surrounding grid lines
I overlaid the two AF layouts to show the difference in extra coverage (shown in red).

Inline image 3

On one hand, the extra layer of AF points is not a huge difference.  On the other hand, the extra AF points allow the D4, D800 and other FX cameras (including those of the previous generation) to touch the intersections of the rule of thirds.

RULE OF THIRDS
Here is what the AF points look like when we overlay a grid that follows the rule of thirds.

Inline image 4 

We can see that the extra AF points are just enough to touch the intersections of the rule of thirds, so even though they aren't huge, they can have a disproportionately significant impact for someone whose composition often follows the rule of thirds (like me).

Solution 1: Golden Ratio
One solution is to consider using an alternative compositional aid, such as the golden ratio.  (Indeed, the rule of thirds is arguably just an approximation of the golden ratio.)  A golden ratio grid places the intersections just a tad closer to the middle of the frame:

Inline image 6

The intersections of the golden ratio grid are close enough to be arguably within the D600's AF coverage.

Solution 2: Crop
An alternative solution is to take advantage of the D600's 24mp resolution by shooting to crop.  If you don't need to make large prints, it might be feasible if you absolutely need to position the AF point at the rule of thirds intersection for a particular shot.  Here is an example where after cropping the AF points cover a couple of the intersections of the rule of thirds:
Gray area represents the area being cropped out
However, this solution might be ok from time to time but is probably not going to be satisfactory on an everyday basis.  Who would want to lose the use of a portion of their sensor?  Besides impacting your lens' effective focal length, this solution also has implications for noise (becomes more noticeable) and depth of field (may become shallower at the same viewing size).

Solution 3: Focus and recompose
Another solution is of course to focus and recompose.   This solution tends to work only for a slow-moving or stationary subject because when there is a very shallow depth of field, usually the subject moves out of focus by the time I recompose.  The D600 is a little better because you can choose an AF point that's a little closer to the subject, but the short delay is sometimes enough to get the subject out of focus.

ALTERNATIVES TO FOCUS-AND-RECOMPOSE
Because focus-and-recompose has its own problems, sometimes I use these alternatives:

Alternative 1: Equidistant Target

In this test shot, my wife's eyes were outside of the AF area:

I therefore focused on her mouth which is about the same distance from the camera as her eyes.  Focusing on her mouth therefore got her eyes in focus as well.


Alternative 2: Auto Area AF

Another alternative is to use Auto Area AF (I generally pair it with AF-C).  In this mode, the camera chooses the focal point.  I hadn't tried this before because I was reluctant to give up control over where the camera would focus.  However, when I tried it, it seemed that for some reason, the camera would focus on the right spot, sometimes even when the camera appears to choose the "wrong" focus point.

In this shot, I manually chose the focal point over my daughter's eye.

f/2.0
To me, the focus is pretty good considering that my daughter was being swung up and down.  Here is the same scene, but this time I used Auto Area AF:


Pinpoint precision (focusing on the near eye)!  Again, this was with our daughter being randomly swung up and down.

Now you may be wondering, how does Auto Area AF offer an alternative to focus-and-recompose?  Well, take a look at these shots:



In both of them, the eyes are well outside the D600's AF coverage, yet the D600 chose AF points that resulted in the eyes being in focus anyway (!)

Here are some bursts that show how the Auto Area AF performs with AF-C.  These shots were taken by my wife who doesn't know anything about photography.  Needless to say she doesn't try to confirm the location of the AF points.  Note that the eyes are sometimes outside the AF coverage yet they are still in focus.

Burst 1:



Burst 2:



Burst 3:






As you can see, Auto Area AF isn't perfect but it gets the focus right a surprising amount of the time.  When I reviewed the Nikon D3, I noted that the autofocus wasn't as 'magical' as Ken Rockwell claimed it was.  This one however, is eerily close (and perhaps I was too hasty to discount the D3's auto area AF last time).

Note: One issue with these alternatives is that they can throw your exposure off if you are in matrix metering mode because Nikon's matrix metering will give more weight to the AF point.  In the real world, I haven't found this to be a problem.

FAST-MOVING SUBJECTS
Sometimes subjects were moving fast enough that there was no time for me to select the AF point and position them over the subject.  Instead I had to use Auto Area AF and AF-C and hope for the best.  Here are a couple of shots with this method:

Nikkor 28-105 3.5-4.5D




Nikkor 24-70 2.8G:

Of course this method doesn't work all the time but the hit rate is surprising.  It doesn't usually result in critical focus (with some exceptions like the 24-70 shot above) but the majority of the shots show at least "acceptable" focus (which for me means usable at web viewing sizes or prints of 8x12 inches).

COMPARISON WITH NIKON D3
To give you an idea of how well the D600's autofocus system performs relative to another FX camera, below are some shots with the Nikon D3 that are somewhat similar - the lens is the same, the aperture is also wide, there is a similar amount of activity, and the shutter speed I used was comparable in one of the series.  However, one notable difference is that I used AF-S then whereas I use AF-C now.  Anyway FWIW:

Sample set 1 (f/1.4, 1/800 to 1/1250):





Sample set 2 (f/1.8, 1/200 to 1/400):






MORE SAMPLES
Here are more test shots.  They're just snapshots but they show how well the Nikon D600 can focus in real world conditions.

f/2.0

f/1.4

f/1.8
f/2.0

f/2.0
To conclude, the D600's autofocus is fast and accurate, even in challenging conditions such as low light, fast-moving subjects and shooting with a very shallow depth of field.  Even though the AF points are tightly clustered, there are alternatives that have worked well for me.

RELATED FOLLOW-UP POST HERE: http://betterfamilyphotos.blogspot.com/2012/11/nikon-d600-autofocus-with-fast-subjects.html

RELATED POSTS:
Nikon D600 Hands-On Review
A Miracle Happened Today (Canon 5DIII autofocus)

37 comments:

  1. First to comment :P

    Good points on the auto focus area, the camera seems to perform good. By the way were you using a monopod/tripod or are these handheld?

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    1. lol :)

      All handheld.

      Best regards,
      Mic

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  2. Hi Mic,

    Thanks for your in-deepth take on the subject. After reading your post I'm more confused on the CAM3500 vs CAM 4800 topic.

    The majority of the photos shown are not acceptable for me in terms of focus. True, you were using a unforgiving aperture with unforgiving subjects (kids,... ...I know, I have two :)). That said I'm not sure where was the problem as the focus seems tack on, but the photos are kind of blurred. It might be due to shallow DOF or due to low shutter speed.

    If D600 would have CAM3500FX it would be a no brainer...

    Marko

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    1. Hi Marko. I understand what you mean about the blurriness. I ascribe that to the shutter speed because the sharpest shots tend to be the one where there is little movement, e.g. my son playing with his 3DS. Another potential factor in the blurriness is that these shots have had no sharpening applied (other than LR default).

      Meanwhile, since we're talking about AF accuracy here, the way I judge it is not by the sharpness of the shot but by whether the focus is accurate (based on whether the intended target is the part of the shot that is most in focus, and if not, by how much). As for the CAM3500FX, my impression is that at my shots under similar conditions with my D3 at the same viewing sizes are about the same. I'll look for samples and post them.

      Best regards,
      Mic

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  3. Mic, the comparison with D3 clearly shows the D600 actually performs at least equally good. Marko.

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    1. Thanks Marko. So yes we can blame the blurriness on me. :) lol.

      Best regards,
      Mic

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  4. No. The kids are just too fast :)

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  5. PLease, see my thread here:
    http://forums.dpreview.com/forums/thread/3283874#forum-post-50070069

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    1. Hi marcel. Thanks for posting the link to the thread. I understand your problem. The thing is, there are many variables that could cause the shot being out of focus. Some of the factors have to do with the equipment (camera or lens) while others have to do with the user. Have you been able to get sharp shots under the same conditions (including same lens and aperture) with another camera? If yes, then probably it is a camera issue. If not, then probably it is a user issue (which is good news because you can correct it with proper technique).

      Best regards,
      Mic

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    2. Thanks for the reply. I guess I have to learn to deal better with the options of the D600 AF-C. Also was trying to stay focused to 1.8 which is very shallow. I'll try again.
      I'm also debating in the forum which would be the fastest AF lens to focus children running and playing. What do you think?

      Delete
    3. Hi Marcel. Yeah 1.8 is challenging enough on the 50mm. On the 85mm I can imagine it must be significantly harder. On top of that you're trying to capture action. That's very challenging for any camera to do. That's the kind of situation where my fingers and eyes probably can't keep up with the action (the moment you do, the area in focus has probably moved on) and what I would probably do is to do a focus trap. Put the camera on focus priority, hold the shutter down and wait for the camera to get something in focus then it will release the shutter. I lose the choice of the moment, but I can try several times.

      Fastest AF lens -- hmm I can only comment on my personal experience. The 24-70 2.8G and 28-70 2.8D seemed to focus most quickly among the ones I've tried. (Note: the 28-70 doesn't have a focus motor - I was using it with a D3).

      Best regards,
      Mic

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    4. Hi Marcel. Just got an 85 1.8G last night. One thing I can say is that the AF speed is not so good, compared to my other lenses. That could be a factor in your shots. However, I will try to shoot some action with it and post the results.

      Best regards,
      Mic

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  6. Just commenting on the perceived lack of sharpness in your images.

    I found that with my D600 I first opened the images in LR and also wondered about lack of perceived sharpness but then zoomed in to 1:1 and saw the detail resolving power was fantastic. As we know the eye's perception of sharpness is the 'sharp' line between different elements of the image, which is actually a distortion. So the D600 default settings provide high resolution but not high perceived sharponess (that is, there's not a lot of contrast applied to the different elements of the image). (Hope I got that basically right).

    Solution: I set my sharpness in the camera Picture Control (D600 manual, page 132) to Sharpness +6. Now the images look 'sharper'.

    For the previous images, I just increased the sharpness in LR.

    From Tony from Australia
    Hope that helps.

    Tony

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    1. Hi Tony thank you very much for sharing your observation about sharpness. Yeah SOOC shots can certainly benefit from sharpening. As for me, I normally don't sharpen unless there's detail that I want to emphasize. Sometimes I find that sharpening is counterproductive for some subjects (cough, cough) :)

      BTW you mentioned previous images -- in case you wanted to post pics maybe you can post a link to them because they didn't show up in the comment.

      Best regards,
      Mic

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  7. Any possibility of a test on the D600's AF system in low-light AND with moving objects?

    I'll be frank: I'm asking because, in a recent youtube video, comparing the D600 with a D800 and a 5D Mark III (yes, I'm talking about the digitalrev video), the guy simply cannot get the camera to lock focus on the subjects. And the worst part is that the place looks decently lit. "Frustrating" is the word he uses to describe the D600's AF...
    (And yes, the other cameras were locking focus well in the same conditions).

    Would it be possible for you to do a small test, similar to that one, and posting your thoughts.

    Thanks in advance!

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    1. Hello there. I haven't seen the digitalrev video but I'm surprised at Kai's opinion. Anyway, sure - I'll be glad to test the D600 with fast subjects in low light. Check back to see the results.

      Best regards,
      Mic

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  8. I thought I'd pop in with my opinion as a 5D Mark III owner, Mic certainly will reply.
    Anyway, I saw the same digitalrev video, one thing you have to note, Kai uses all points auto area AF, most of the time, he raises the camera to his eye and just press the shutter, depending on the camera to select the correct focus point correctly and accurately.

    However, this method lacks control, as the camera might not always pick the subject you want, so most people usually use single point focus, and choose the focus point. Back to the video, if you leave the choice of the auto focus points to the camera, then the D600 is at a disadvantage because it has it's cross type focus points clustered atthe center, and any subject moving away from these points, in dim light, will not be easily focused upon.

    But, if you use single point cross type and compare the D600 and the 5D Mark III, they will focus equally quick, and both have the same -2 EV capability of low light focusing, even my famously bashed 5D Mark II would focus as quick and as accurate using the center focusing point.

    I hope my opinion was of value, and anyway, you're comparing a $2k body to a $3k body, the D600 ia real bargain.

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    1. I think you're right Mohammad. When I use Auto Area AF, there is a slight but perceptible delay compared to using single-point AF. And that's a good point, about the location of the cross-type AF points. Anyway, I will try both.

      Best regards,
      Mic

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  9. @mshafik: I think that, at one point, Kai especifically said "even in single point, the D600 won't lock focus". But I can't be 100% sure right now.

    @Mic Ty: Thank you for the quick answer. I hope you have the opportunity to see the video in question as well.

    Looking forward to that test of yours. Thank you very much in advance.

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    1. Hi! I found the video that you're referring to, with the boxing shots. You're correct, at around the 6:15 mark, Kai does say it is frustrating even with single AF point. The way he holds his camera in front of his face is kind of strange and looks unstable but I'll try to get a shot under similar circumstances. I believe he was using the 24-70 2.8, so I'll use that one too.

      Best regards,
      Mic

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    2. Check out this follow-up post: http://betterfamilyphotos.blogspot.com/2012/11/nikon-d600-autofocus-with-fast-subjects.html

      Delete
  10. Brilliant, thank you. (indeed, it was the 24-70)


    And congratulations on the excellent blog. Very helpful.

    Keep up the good work.

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    Replies
    1. Whoa... :-O

      And thanks! ^^

      Best regards,
      Mic

      Delete
  11. Hi Mic

    Your review is very well explained, Im glad I stumbled into your blog. Anyway I just want to ask, did you use a flash in the above pictures? If so, built in flash or speedlight? If not what iso's where those pictures taken?

    Thanks,

    Fred

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    1. Thanks Fred. Yeah not a lot of folks know about our blog so we need all the help we can get to spread the word. Anyway, all shots were ambient only. I dont know the ISOs off the top of my head because I usually use auto ISO up to 12800 (or 25600 if necessary) but you can check the exif. Hope that helps.

      Best regards,
      Mic

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  12. Thanks for he reply mic, great shots by the way despite ambient light without flash they were tack sharp. It makes me happy I bought the D600 which looking at your pictures performs well even on high iso's.. One thing Im concerned with my D600 though, unlike my D90 my shutter wont release if subject is out of focus using an AF-on button. With the D600 it still snaps even if its out of focusand even with atofocus set on focus and not release mode. I hope I made myself clear =) Did yoiu have that issue on your D600 Mic?

    Fred

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    1. Hi Fred. I think your D600's behavior is not normal. Mine definitely doesn't act that way. There could be any number of reasons for your camera's strange AF. My suggestion is to start by eliminating as many variables as you can -- take a shot of a stationary subject using a tripod and remote release with manually selected focal point, in AF-S mode, focus priority, with a lens that has had AF fine-tuning. Perhaps even reset the system beforehand. You should be able to get a tack sharp shot with that. Then introduce additional variables one at a time. I believe if you do it that way you will be able to isolate the cause of the strange behavior.

      Best regards,
      Mic

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    2. Mic did you assign the AEL as AF-on button? That would be custom menu settings > control >f4. With my D90 you cant push the shutter if you move the camera out of focus however not with the D600. Anyway I will try to rule out things but I read in some other forums this is the new thing with D4, D800 and D600.. I think nikon changed it in their new fx line up..

      Delete
    3. Hi Fred. You're right when I tried assigning the AE-L button as the AF-ON button, the shutter will release whether the AF point is in focus or not. However, I found a workaround. If you want to use trap focus, then first of all, use focus priority as you said. The other thing is to hold down the AF-ON button then press the shutter. I found that when I do this, the shutter will not release unless the AF point is in focus. I hope that helps!

      Best regards,
      Mic

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  13. Mic it does work when you're in AF-C mode however shutter triggers despite out of focus on AF-S and AF-A on focus priority which contradicts what is said on manual page 97 where it states there that if focus priority is used on AF-S, shutter can ONLY be released when in focus indicator is displayed which is clearly not the case. Do you think this is a bug that Nikon can address by a new firmware?

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    1. Hi Fred, I think I wasn't very clear. What I did was to hold down the AF-ON (AE-L) button. While the D600 is still trying to focus, I hold down the shutter all the way. If I do this, the shutter does not release until after the target is in focus. As soon as the target is in focus, the shutter releases. So it is similar to a focus trap. Is this the function you are looking for?

      As for whether Nikon will ever fix this, your guess is as good as mine. However, I suspect they will not because this seems like an intentional design change.

      Best regards,
      Mic

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  14. Yes it does exactly that but what concerns me Mic is that after you get a focus then recompose to a different subject which is out of focus while still pressing on AF-on button, shutter still triggers even if that new subject is out of focus. That is not the case with my D90, doing the same procedure shutter can not be released if you recompose to a different subject which is out of focus...

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    1. Yeah, I hear you. What I did is to move the AF point to the new subject and press the AF-ON button again, then hold down the shutter again for the focus trap. Not sure if that would work for your shooting style...

      Best regards,
      Mic

      Delete
  15. Thanks a ton for ur review
    it helped immensely

    i too shoot my / other kids
    and do so with a d7000

    fedup of its hit and miss autofocus issues

    my friends d300s is way better
    mostly for the cams better focusing strengths

    not too happy with the d600 results

    I am quiet a nazi when it comes to focusing
    need a hit rate of 9/10

    though the d4 sounds like it was built for me
    i dislike its weight and price

    now waiting patiently for the d400 / d500

    the d800 mp raw editing is a killer of slow comps

    investemtns in other nikon gear
    is preventing me from jumping over to canon
    which too has issues of its own .




    ReplyDelete
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    1. Thanks and I'm glad you found the review helpful.

      About focusing I used to be very particular about it too. But then I saw some of my favorite photographers (Ryan Brenizer for example) whose shots were not always in perfect focus. Also, I noticed that in movies and TV shows, the focus is sometimes not perfect. It made me think twice about my need for perfect focus.

      If focus is extremely important to you, you may want to check out my coauthor mshafik's posts about the Olympus OM-D. It has what I would consider to be the ideal AF system: fast, accurate, very smart in auto mode (automatically picks the near eye of human faces). I know you've made a lot of investment in Nikon but in the long run you may be better served by the OM-D or some similar camera.

      Best regards,
      Mic

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  16. Hi Mic! I have a problem! When I photo manually my camera is set on the single point autofokus area and I don't know how to change it to the Auto-Area AF or Dynamic-Area AF. Ive been searching and searching but cant find it in the manual! Could you please explain what buttons i should push to choose these settings? Thanks!
    /Ellen

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    Replies
    1. Hi Ellen! On the d600's lever for adjusting AF there is a button. Hold down that button then rotate the front command dial to change AF points from one to 39 to auto etc. you can also rotate the rear dial to change from AF-S to AF-A to AF-C. Pls note some AF point modes such as dynamic are not available when you are using AF-S. hope this helps!

      Best regards,
      Mic

      Delete

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