D800 Face Recognition

<p>I am a recent adaptor of the D800 and still learning it. I assume my comments here also apply to the D4 and D600.<br /><br />I was confused by how face recgonition worked in the viewfinder, I am not interested in live view. I did some research and found that the vast majority of people who discuss the topic on web forums are even more confused than I. Here are my concusions, do they jive with your understanding of viewfinder face recognition?<br /><br />1) Face recognition must be divided into two topics, Focus and Exposure.<br /><br />2) Focus is relatively simple, it only works in AF-S Auto and AF-C Auto, the only difference being, of course, that AF-C tracks. The Focus system simply gives priority to faces that it detects within the AF region and selects the closest focus point to the face. There is no indication that the camera is using Face Recognition, it simply does it.<br /><br />3) Exposure uses faces anywhere in the viewfinder and is not limited to the AF region, and works even when the AF mode is not Auto. If the camera detects a face anywhere in the viewfinder it gives Exposure priority to that face making, for example, back lit subjects easier to shoot. The face that is detected is indicated, unlike the focus point, in Playback whenever you zoom in on a photo by a white box in the inset photo, different from the yellow box that indicates the level of zoom.<br /><br />Thats it, or at least my understanding of it.</p>

<p>My understanding is that "face recognition" works only when in AF-S mode with AF Area Mode set to Auto-area AF. Selection of the focus point is performed by the camera and preference is given to "faces". </p>

<p>The user's manual does not specify whether or not exposure is weighted to the area chosen by the auto-focus. My experience suggests that, with matrix metering, exposure is significantly biased by the area under the chosen AF point in all Autofocus modes.</p>

<p>A simple experiment can confirm this. Use AF-C mode. Frame an image with significantly varying illumination within the frame. Move the selected AF point between bright and dimmer portions of the frame and observe how the exposure changes.</p>

<p>I will try that experiment with exposure.<br /> <br />However, face recognition focusing works both in AF-S and AF-C in Auto. I have confirmed that.<br /> <br />And face recognition for exposure works regardless of AF mode, I have also confirmed that. This is true even when the focus point and the face recognition area are not in the same spot, as when the face is not in the AF region.</p>

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<p>However, face recognition focusing works both in AF-S and AF-C in Auto. I have confirmed that.</p>

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<p>You are right. AF Area Mode can be set to <strong>Auto-area</strong> in both AF-S and AF-C. In both cases the initial focus point is <em>selected by the camera</em>. When using any other AF Area Mode, where the initial focus point is <em>user selected, </em>exposure is highly influenced by the area under the focus point. Thus it is logical that this would also be the case for Auto-area mode. I am not sure how one would confirm that.</p>

<p>Not too many responses here so far. At least tell me if you have noticed the white rectangle over the face different from the focus point when you zoom into a photo in Playback. </p>

<p>I think a number of different face detection functions are being (con)fused into one here. From my use of the D800 and reading of the manual, my understanding is it works like this:</p>

<p>The white squares seen in review mode are nothing to do with the AF system, but are there so that faces can be zoomed in on during playback. Page 231 of the manual indicates that up to 35 faces can be detected. The front thumbwheel rotary switch allows jumping from face to face. The white squares will go away if the "lock/?" button is pressed.</p>

<p>Face priority AF is only available in Live View mode - see p. 49.</p>

<p>In normal viewfinder use, face detection only operates in Auto-Area AF mode (p. 94) and then only when a face is within the AF point central area. In any other AF mode and at the perimeter of the frame there's no automatic face detection.</p>

<p>While I do admire many of the innovations of modern DSLRs, the Auto-area mode (face recognition) is something I never use. I do not wish the camera to select the focus point for me. Thus I have had no occasion to notice the white rectangle; sorry. My guess is that most users share my sentiments, thus the dearth of responses.</p>

<p>Joe, you are confusing live view and viewfinder face detection when you talk about 35 faces. This is exactly what I was talking about in my original post, people do not have a good handle on face detection. <br>

You seem to understand AF face detection in the viewfinder, but not face detection for exposure. The white box in Playback indicates the face that was found by the exposure system, not the AF system. see number 4 here: http://nps.nikonimaging.com/technical_solutions/d800_d800e_tips/quick_tips/ Of course Nikon is a bit criptic.<br>

Mike, the white triangle in Playback mode is not AF, it is exposure.<br>

I am quoting here but it is right on the money - "If you want to use the Magic you have to know the spells"</p>

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<p> The white box in Playback indicates the face that was found by the exposure system, not the AF system. see number 4 here:</p>

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<p>The white rectangle is indeed only found when one is in Playback. It helps to identify faces. It has nothing to do with the exposure nor with the focus point. It is another function which I never use.</p>

<p>Tip #4 is appropriately vague; it says nothing about the white rectangle seen in Playback, but simply restates what I and Joe have already said. When the selected focus point (either user selected or Auto area) is on a face, the exposure will be adjusted to properly expose that face. </p>

<p>Nowhere is it suggested that using Auto-area mode will automatically select faces to the exclusion of all else. Concerning Auto-area mode, the user's manual does state:</p>

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<p align="LEFT">If a face is detected, the camera will give priority to the portrait subject.</p>

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<p align="LEFT"> </p>

<p align="LEFT">Meaning priority in terms of focus and exposure.</p>

<p align="LEFT">Given that you are a "recent adaptor (sic) of the D800", I am happy you have mastered the Spells so quickly. Nevertheless you may still learn something from those who have been using the camera for several months.</p>

<p>"Joe, you are confusing live view and viewfinder face detection when you talk about 35 faces." - No, I'm not. Both in Liveview and review mode, face recognition can be up to 35 faces. Check your manual.</p>

<p>Joe you are right about review mode.<br>

The issue is when you say:<br>

"In normal viewfinder use, face detection only operates in Auto-Area AF mode (p. 94) and then only when a face is within the AF point central area. In any other AF mode and at the perimeter of the frame there's no automatic face detection."<br>

This is true of AF. This is not true of Exposure. I assume you did not read the link that I supplied, here are the quotes from the Nikon site:<br>

"The RGB sensor with approximately 91K (91,000) pixels built into the D800/D800E offers more accurate face detection. When used with viewfinder framing in exposure modes other than M, the camera balances exposure between a portrait subject and the background, even when the subject is backlit."<br>

"D800/D800E: The camera uses face detection to ensure optimal exposure of the subject's face."</p>

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<p>The white rectangle is indeed only found when one is in Playback. It helps to identify faces. It has nothing to do with the exposure nor with the focus point. It is another function which I never use.</p>

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<p>But it does, and you do use it if you use any exposure method other than M. For example, if you are focusing manually, taking AF out of the equation, and the camera detects a face, later indicated by the white box, Exposure will give priority to that face whether it is in focus or not.</p>

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<p>Nevertheless you may still learn something from those who have been using the camera for several months.</p>

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<p>I am grateful, I honestly read your posts and I think about them. I don't always agree.</p>

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<p>But it does, and you do use it if you use any exposure method other than M. For example, if you are focusing manually, taking AF out of the equation, and the camera detects a face, later indicated by the white box, Exposure will give priority to that face whether it is in focus or not.</p>

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<p>Much has been written about the operation of Nikon's Matrix exposure. It is stated that the "Advances Scene Recognition System" uses a vast data base of images for comparison to what is captured by the RGB sensor. In this sense recognition of important objects (whether they are faces or something else), particularly when they are in the foreground, plays an important part in biasing the exposure. </p>

<p>Note also in the Nikon tip you cited, it does not specify that the area mode was set to Auto-area. I am sure the same result would be obtained with other autofocus modes. Also I would bet that the same exposure would have been obtained if the bride had been replaced by a white rose bush. </p>

<p>I cannot agree with the argument that exposure will give priority to any face anywhere in the image, if that face is identified by a white rectangle in Playback. In any case I am sure that the longer you use the camera and carefully observe the results, the better you will be able to predict its behavior.</p>

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<p>I cannot agree with the argument that exposure will give priority to any face anywhere in the image, if that face is identified by a white rectangle in Playback.</p>

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<p>From http://imaging.nikon.com/history/scenes/32/index.htm</p>

<p>"We also bumped the pixel count of the RGB metering sensor up to 91,000 pixels so that faces can be detected even when shooting with the optical viewfinder, making AE even more precise."</p>