Some Nikon D300s focusing system questions

Discussion in 'Digital Photography' started by wheelhot, Dec 1, 2009.

  1. wheelhot macrumors 68020

    Nov 23, 2007
    Hey, recently I've been playing around with Nikon AF modes but there are some that got me confused.

    At the lower front, there is 3 dials; Continuos, Single and Manual. My question is regarding the Continuous and Single Mode.

    To my understanding there is 3 modes; single AF, dynamic AF and the full box which I dont understand what it means.

    The problem is, when in Continuous Mode and Dynamic AF, when I focus lock the subject, as the subject move. The camera did follow but as soon as I press the shutter, the camera will snap the part where the AF point is placed. I don't really understand what is going on cause in 51AF with 3D Tracking, I can see the AF points follow the subject.
  2. compuwar macrumors 601


    Oct 5, 2006
    Northern/Central VA
    Your question isn't too clear to me...

    The front focus control buttons have the follwoing functions:

    (C) Continuous Servo mode, when the shutter button is half-pressed, the camera will continue to adjust focus with its current focus point settings.

    (S) Single Servo mode, when the shutter button is half-pressed, the camera will focus once with its current focus point settings.

    (M) Manual mode, the user must focus the camera lens themselves.

    The rear focus area settings have the following functions:

    The big white box lets the camera try to determine what's in focus by itself using any of the AF sensors it chooses.

    The small box with four dots ("crosshair" mode) allows the user to choose a focus point and the camera to adjust that point to follow action.

    The small box by itself allows the user to choose the focus point.

    These work in combination with the other AF settings:

    a1- AF-C priority - this setting affects when you're in C mode:

    Release- take a picture when the user presses the shutter button

    Focus- take a picture when the AF module determines the subject is in sharp focus

    Release+Focus- take a picture when the AF module determines the subject is probably in focus

    a3- 51 points and 3d tracking:

    Allows the camera to use all AF points, but only works in crosshair mode with AF-C.

    If you're in AF-C with crosshair mode, then the camera starts with the assumption that where you have the AF point when you half-press the shutter button is the part of the subject you want to keep in focus, and it adjusts focus as the camera and subject move to keep that in focus until you hit the shutter, at which point it will take the picture, adjust focus a bit and take the picture or adjust focus a lot and take the picture depending on the priority.

    Now, the caveat is that the D300 has a slower processor than say the D3- so with some moving subjects it's possible to overwhelm the CPU if you try to have the camera do too much, which is why you can switch down to a lower number of AF points and control the AF point selection yourself.
  3. pdxflint macrumors 68020


    Aug 25, 2006
    Oregon coast
    Interesting... I was under the impression that the D300 and D3 had the exact same AF focusing module/processing... etc. I understand that the D300s has a slightly improved XSpeed processor, and perhaps a slightly faster AF than it's predecessor, but it's not a huge leap better than the D300 for AF performance, more a subtle improvement - plus add video. That's the sense I get from all the reading and research I've done...

    I realize this doesn't address the OP's question, but compuwar did a good job.
  4. OreoCookie macrumors 68030

    Apr 14, 2001
    Sendai, Japan
    You confuse two things here:
    (1) There is single, continuous and manual mode. Independent of which AF sensor (or all or a selection of them is used), this will determine what the camera will do:
    (i) Manual: this will disable the AF and just give you a focus indicator.
    (ii) Single (AF-S): this means the camera will focus when you depress the shutter release half-way (or press the focus button) and then ignore movement. If you shoot a still life or a portrait, this is good, because now you can `focus and recompose.' For sports where people are in motion, this is the wrong mode.
    (iii) Continuous (AF-C): now the camera tracks the subject even if it moves. This is good for sports, for instance.
    (iv) There is AF-A where the camera thinks it's smart enough to switch between AF-S and AF-C by itself.

    (2) The second option concerns how the AF sensors will be utilized and whether they work in concert or by themselves:
    (i) Single AF will use only the one AF point that you have selected. It is highlighted in the viewfinder and once more indicated on the lcd on the shoulder of your camera.
    (ii) Dynamic will use not just the AF field you've selected, but also the ones surrounding it to help track the subject. This is only helpful if you use AF-C.
    (iii) All area AF: the camera magically chooses the `right AF sensor' -- well, it tries to. On my D80, it usually focusses on the closest subject.

    All Ken Rockwell haters, look away now: you can find more infos with pictures here. You can also read the instructions specific to the D700 as the AF system of these two cameras are very closely related.
  5. compuwar macrumors 601


    Oct 5, 2006
    Northern/Central VA
    What I've read (I don't have a D300 or a D3, I have a D2x and a D3x) says that the D300 can be overloaded while the D3 can't in terms of AF targets/sensors/performance (Including the KR link that Oreo references.) I suspect like most Pro/Prosumer camera issues, the major difference lies in edge cases that most people don't hit, but when you need it, you need it.

    FWIW, the D300 isn't really a "predecessor" as I understand Nikon camera development. The high-end Dn and what I'd call "prosumer" Dnnn series bodies are developed by different teams, parts re-use is a design goal, but the development cycles are long enough that the D3 and D300 were being developed at the same time, the D3 team had some issues that made them "late" in terms of schedule which is why for a short period of time, the D2xs was "worse" spec-wise than it's lower-priced sibling D300.
  6. wheelhot thread starter macrumors 68020

    Nov 23, 2007
    Thanks for the replies guys. I know my question is a lil bit confusing cause I myself don't know how to properly write it, but thanks to Compuwar and OreoCookie. I finally got an idea how the D300s AF system works.

    Now I have a question, if I set to AF-C and chose single point AF / all area AF will it track the subject also?

    And how do I get to AF-A?

    Anyway, regarding the AF system diff between the D300, D300s and D3. From what I read, it seems many agreed that the AF system is faster on the D300s then the D300 and comparable to the D3/D700. Reason due to the possibly improved Expeed processor that we will not know for real cause Nikon doesn't keep to numbering its image processing chip like Canon does with the Digic III, Digic IV and etc.

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