What do you think???

[Rick Waller]

<p>"My one concern about a D3 or later is that the coverage of AF points seemed to be an issue. They are much more spread across the frame on a DX camera dues to the mirror box geometry"</p>

<p>Out of curiousity, why does the distance between the AF points matter? When shooting in single focus mode, I just place the point (whichever one I choose) over the point of critical focus. When shooting in continuous "follow focus", I place the center point over the desired area of focus and the machine does its thing handing off the focus to whichever point it decides it needs to. I shoot sideline sports and began with a D2h and a D2x, which were of course DX bodies and graduated up to the D3 when it came out and never noticed one bit of difference in the focusing. If anything, while I never shot with DX and FX at the same time, my impression was that the AF in the D3 was better than that in the DX bodies.</p>

<p>Not disagreeing with your comment - just trying to understand the issue. It is something that never crossed my mind.</p>

[chip_chipowski]

<blockquote>

<p>Okay I've read all your responses or opinions on the above question and I thank you so much. So it's my turn now...</p>

</blockquote>

<p>+1 to John Miller for a thoughtful discussion. Very interesting to read your comments about gear preferences. So many of your choices run counter to "prevailing wisdom" but you clearly know how to use these tools skillfully. </p>

 

[dan_south]

<p>John makes a good point about autofocus points on full frame ("FX") camera bodies. The AF sensor is considerably smaller than the image sensor, so the AF points will be clustered in the middle of the FX frame.</p>

<p>One benefit of newer cameras is shooting in Live View, i.e. looking at the LCD screen instead of through the viewfinder. Granted, this has limitations. Autofocus is slower, you can forget about fancy AF-S modes for following action, and Live View is not very practical in bright sunlight where the LCD screen is difficult to see.</p>

<p>But autofocus in Live View also has a number of advantages.</p>

 

<ul>

<li>It's very accurate because it's based on contrast in the actual image.</li>

<li>It does not require AF micro fine tuning.</li>

<li>The focus point can be placed ANYWHERE in the frame.</li>

<li>On the latest generation of models (D800, D4, D7100, etc. - maybe the D3s, but I'm not certain), the mirror stays up, effectively reducing vibration as in Mirror Lockup Mode.</li>

<li>Multiple useful display options are available.</li>

</ul>

<p>Live View will not replace Phase Detection (viewfinder) autofocus for everything, or even the majority of things. But when you really need to focus on something at the far edges of the frame - or even between normal AF points - the option exists.</p>

<p>I would caution, however, that the cameras in the D3, D300, D700 era had a cumbersome Live View implementation. The mirror closes and re-opens before the exposure occurs. So, if you want to consider using Live View at some point, invest in a later model body with the more efficient mirror-stays-up implementation of Live View.</p>

[Andrew Garrard]

<p>Eric wrote:</p>

 

<blockquote>Out of curiousity, why does the distance between the AF points matter? When shooting in single focus mode, I just place the point (whichever one I choose) over the point of critical focus. When shooting in continuous "follow focus", I place the center point over the desired area of focus and the machine does its thing handing off the focus to whichever point it decides it needs to. I shoot sideline sports and began with a D2h and a D2x, which were of course DX bodies and graduated up to the D3 when it came out and never noticed one bit of difference in the focusing. If anything, while I never shot with DX and FX at the same time, my impression was that the AF in the D3 was better than that in the DX bodies.</blockquote>

 

<p>I was just responding to John's stated concern:</p>

 

<blockquote>I really like the fact that the focusing points are spread out over the frame not grouped in a central area where it's hard to set the focusing where you really want it at times.</blockquote>

 

<p>The Multicam 3500 in the D3 and derivatives is a much advanced model over that in the D2h and D2x - but the geometry of the mirror means that all the AF points <i>are</i> nearer the middle of the frame, particularly compared with the same Multicam 3500 when used in the D300 or D7100. (The autofocus module covers the same sensor area on each camera, but the sensor is bigger on the FX cameras, leaving a gap around the edges.) Everything's fine so long as the thing you want to autofocus on is actually within the region covered by the AF sensors, but they barely reach to the "rule of thirds" points on an FX sensor. This is an artifact of the mirror geometry, and not unique to Nikon.<br />

<br />

Of course, you can "focus and recompose" (with the nearest AF point), but that necessarily introduces some error as the focal plane rotates with the camera. And you don't have any way to compensate for you or the subject moving slightly.<br />

<br />

Live view (contrast-detect) focus has its own limitations, especially with a moving subject - the camera can detect whether something is out of focus, but not "how much" and "what direction", unlike phase detect. But for a static subject, Dan is quite right that it has advantages. I'd also point out that the D800 has some live view issues (it doesn't display full resolution at maximum zoom), but that isn't necessarily a sticking point.</p>

[Rick Waller]

<p>Hmmmm Andrew. Did not know that. I will have to fool around with my D3 and D3s a bit to see if I can replicate the effect. Are you saying that once I lock on the focus with say the center point and the subject moves to the edge of the frame, beyond the farthest sensor, the camera will lose AF? If this is so, in practical terms for my shooting, it makes no difference since when shooting fast moving atheletes, once I lock on the initial focus, I almost always pan with the camera so that the subject is always within the actual AF point array. Either I have never allowed a moving subject to get out beyond the outer AF points, or if I did and got poor results, did not understand what was occurring and attributed the blown shots to poor technique on my part.</p>

<p>I guess we are never to old to learn. I am going to go out and try out your explanation. Fascinating.</p>

[Andrew Garrard]

<p>Hi Eric.<br />

<br />

Yes. The camera can only "see" autofocus at the autofocus points (which are not quite the shape and position suggested by the AF indicators in the finder, but are pretty close). The camera can't autofocus at the edge of the frame using the phase-detect (mirror down) focus mechanism.<br />

<br />

I can understand having the camera set to release priority for athletics - the shutter will release anyway even if there's no AF module there. And I can understand trying to keep the athlete under the AF points when in motion (and cropping in post-production). If you're tracking, it's fairly likely that you'd be within reasonable depth of field anyway - the AF system does contain some prediction, and 12MP is moderately lenient for focus errors. For me, it's more of a problem with relatively static scenes, where I'm trying to focus on an off-centre subject. Unfortunately, "relatively static" (static enough to allow time for creative framing) doesn't mean "static enough for fixed-focus", especially allowing for me and the subject to move a little. Include the difference in focal distance that comes from the focal plane rotation if you focus-and-recompose, and it <i>is</i> unfortunate that the AF points don't cover the entire frame. Unfortunately, ye cannae change the laws of physics (without adding a bigger mirror box) - even phase-detect-on-sensor mirrorless systems usually can't cover the entire frame with phase-detect modules. Contrast-detect is easier - it just needs to look at the captured picture.<br />

<br />

Good luck!</p>

[Rick Waller]

<p>Andrew - Never knew any of the science. I suppose I have simply been blissfully ignorant and never noticing that the camera won't focus at the edges. To the best of my knowledge, I have never attempted AF on the fringes beyond the AF points. I have explained my technique when shooting moving subjects and apparently the panning effect mitigates the problem since I cannot think of a single time that I intentionally panned with the camera and allowed the subject to be beyond the AF points. </p>

<p>For times when I am shooting in static mode, I will select an AF point, place it over the preferred focus subject and then shoot. So again - I never noticed that there was a problem. I did however notice that the outer AF points are not as sensitive in AF ability as the center point. Many years ago, when I first learned to shoot with an AF camera (F5 if I recall), I would simply place the center AF point over the intended area of focus, locked the focus and then recomposed as necessary to achieve the framing I desired. That way I always knew that the camera was AF'ing to its best ability and didn't worry that some outer points might not be as effective. Still do it often today.</p>

<p>It is sort of like the early days of in camera metering where it was center weighted (or spot if I go back to the original Pentax) only. To get best exposure, when possible we walked right up to the subject, metered the scene and then stepped back to recompose keeping the aperture and shutter where it was when we got in close. </p>

<p>Interesting conversation. My apologies for dragging the thread off the original poster's topic, but I never miss an opportunity to learn something new.</p>

[Fotos53]

<p>Here's my response to the focusing points being spread out on a D2Xs or D2Hs and not being so centered...</p>

<p>How many times have you been in a situation where you wanted the focusing at the edges of the frame and not the center? I don't like to lock-up focus and recompose, it's takes up to much time and what if the subject moves or you're shooting a long lens wide open and the depth of field is a couple of inches at best. So if you picked a single focusing point at the edge of frame...the camera will continue to auto-focus for you and the frames will be sharp.</p>

<p>It couldn't be easier to do and that's why I like the points to be all around the frame.</p>

[Fotos53]

<p>To Chip...thanks for your comment! </p>

<p>Since as you stated so many of my choices run counter to "prevailing wisdom". My camera and lenses choices are not just different or weird, they're carefully thought out of what's the right the equipment for me to use. </p>