Single focus point v. 39 focus points
I am making the (for me) huge leap up from a D80. I shoot mostly wildlife, often birds, with zoom telephotos, and landscape (often sunsets over water) and set my D80 to use the larger (think it is 12mm) center focus & AF to AF-C. I almost never use the focus points (unless using the flash on auto (green).
So, I wonder if using the 39 focus points will actually capture birds in flight. I also set my AEL-AFL button to focus and use the shutter 1/2 press to exposure, then often reframe to the original object focused upon and shoot. I think I will continue with this practice, but am listening.
I have never "gotten" why folks want the multi focus points.
Would you (& others) care to address this?
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#1. "RE: Single focus point v. 39 focus points" | In response to Reply # 0MotoMannequin Registered since 11th Jan 2006Sat 22-Sep-12 02:34 PM
In focus tracking, the newer cameras use info from the color matrix meter to determine if the subject has moved off your chosen focus point and can switch to a different AF point to continue accurate tracking. For fast moving action with high magnification i.e. birds in flight, this can be a tremendous advantage.
On the 51-point cameras I use this in a limited fashion (9-point or 21-point) since I have had situations where I panned with a bird launching off a perch, and in review, the AF point followed the perch off the edge of the frame as I panned. Remarkable tech, but of course not what I wanted. Limiting the number of active focus points lets the camera know, yes the think near the middle of the frame is where I want you focusing.
In landscape shooting, portraits, or anything where my subject is stationary, then absolutely I use single-point AF. In this case, the only thing the additional AF points buy you is you can choose one off-center if that's where your subject is, and then you don't need to focus-and-recompose as much. This doesn't matter so much if working from a tripod, where you should use LiveView for contrast detect AF anyway and that's not tied to the AF points.
Larry - a Bay Area Nikonian
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#2. "RE: Single focus point v. 39 focus points" | In response to Reply # 0nrothschild Registered since 25th Jul 2004Sat 22-Sep-12 02:47 PM
What I'm going to say has applied historically to the 5 Nikon camneras I have shot. The specific performance of the D600 will have to stand the test of time as wildlife photographers use it. You might get a hint from D7000 shooters since that is probably the closest AF engine in a camera that has been out there for awhile.
In general, the fewer focus points that a camera is watching the more attention it pays to each focus point. It has finite processing power and when using multiple focus points that finite processing power is "multi-tasking" each focus point.
The above suggests that the most accurate focus is achieved with a single focus point.
If you are tracking a single bird in flight then you may not be able to keep that single focus point on the bird. If you can't then you lose focus entirely, rather than maybe getting marginally worse focus with 9 or 21 point dynamic focus, for example, on my D300 and D700.
Because the right number of points to use depends on your skill only you can find the perfect happy medium.
I generally use 9 focus points for BIF because I know from experience that one is not enough, and 9 is usually enough if I am on my game.
I have no opinion on the relative efficiency of the D600 when used with the various clusters of focus points and at this point I doubt anyone has enough experience with this type of work on that particular body to come to a firm opinion.
When I shot the D200, which is very similar to the D80 in focus setup, I also tended to use it with "large" focus sensors. When I got a D300 and then D700 I always used the smaller sensors, and 9 pt with tough moving subjects.
I'm not sure now why I used the D200 with large sensors. But I did not shoot a lot of BIF with it. I used a D2h for that. With the smaller modern sensors I like to have a smaller "focus target area" to make sure the camera is focusing on what I think/hope it is. The larger sensors can pick up unwanted subjects at some other distance.
If, for example, using larger sensors on the D80 you might want to change to the smaller sensors only if your images are sometimes mis-focused because the larger sensor grabbed something other than the precise subject you were aiming for. That principle should apply to the D600. So again, your images will tell you if you need to change strategy and settings.
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#3. "RE: Single focus point v. 39 focus points" | In response to Reply # 2EYeye Nikonian since 16th Sep 2012Sun 23-Sep-12 12:43 AM
Sincere thanks to both of you for taking my question seriously and giving thoughtful and helpful answers.
It happens that my D80 always focused "well", in that I did not experience either the front or rear focus issues I have read about a good deal reference the D7000. I could track Osprey and Eagles in flight with the "wide" single center focus point. Woodpeckers & flickers were more difficult. Landscapes of course, not an issue, as were whales in the ocean.
I wish I could get this site to allow me to post my D600 "real world test shots", where I went out in various lighting situations and played with the focus points, the ISO, and aperture settings similar to my film days. I saw "rear focus" in flowers, where the camera picked a petal or stem "behind" the bloom I had "put" the focus point.
From your posts I now wonder if many of those complaining of rear (and front) focus were experiencing instead the focus points being "wider" than the target, as you have explained.
BTW: I am VERY pleased so far with my D600 in FX mode, and also with DX shooting the 16-85mm 3.5/4.5 VR. The MP is even a bit better than D80 as is dynamic range and low light capabilities, in both DX and FX.
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#4. "RE: Single focus point v. 39 focus points" | In response to Reply # 3nrothschild Registered since 25th Jul 2004Sun 23-Sep-12 07:00 AM
I think there are 3 great mysteries in the modern age:
1. The nature of dark matter, if that is what it really is
2. The nature of dark energy, if that is what it really is
3. The nature of autofocus error reports: equipment failure or user failure?
As you point out, the issue of giving a focus point (or a cluster of points) two targets at different distances is also a very complex issue. My D2h would consistently and repeatedly pick the background target, which was the biggest problem I had with that camera.
The problem was compounded because the sensors were very widely spaced and it was well known and easily proven that the actual AF sensor extended far beyond the small viewfinder reticle outlines. If you gave it one unambiguous target it was absolutely state of the art.
My D200 improved on that particular issue, although it was generally not in the same league in terms of tracking fast moving targets, and I found that the D300/700 improved things further, but it may also have been simply the benefit of more and smaller AF sensors. And with those cameras (300/700) I never found that the AF sensors extended very far, if at all, from the reticle outlines.
And the 51 pt AF viewfinder reticle positions are packed so tightly that if it did extend beyond the reticle then it would arguably be "sensor bleed" where the adjacent sensor was used. In other words... is it possible for two adjacent sensors to be reading the same area, and if not then it would be impossible for the sensor to extend beyond the indicated reticle outline.
I think you are taking the correct approach- methodically studying the results and not assuming that any deviation from your expectations are some sort of "failure".
The most interesting aspect of the D600 (to me) is the new f/8 specification. It implies that even at wider apertures the AF engine should be more responsive to difficult targets- dark targets and low contrast targets. But that is just a hunch.
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