Spot metering Advice

<p>Hi Experts,</p>

<p>Been a long time I asked a question here, so here I am so as you all experts : ) ...<br>

I have thinking & working a bit on backlit portraits which has brought me to this question on spot metering.<br>

Q: Does it matter to reading & exposure if I spot meter by filling in the frame vs i spot meter with whole scene.<br>

in other words: Will it matter if I spot meter a portrait face with 100mm telephoto lens vs 18mm wide angle lens.<br>

Just to clarify, I am not recomposing my shot. I am standing at same spot and using above two lenses with spot metering in both scenarios.<br>

Besides this question if anyone has expert advice on backlit portraits I am all ears&eyes now. Thanks as always.</p>

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<p>No, it doesn't matter. The whole point of spot meter is that it meters only from one spot. So, it doesn't matter what the rest of the frame looks like. For example, if I were to take an apple and spot meter off of it, it would not matter if it were on a black background or a white background; my camera would choose the same exposure. If you now move to center-weighted metering, however, my camera would base the exposure mainly off of the apple, but then it would look at the rest of the scene and make a slight adjustment accordingly.</p>

<p>It does matter. That's the short answer because you use the built in spot meter. If you use a hand held spot meter then it doesn't. The spot covers a larger area of the person when you use the wide angle lens and at the same distance from your subject. <br>

For portrait? Incident light meter is more reliable and easier to use than spot meter.</p>

<p>It probably will. Whether it matters depends on the size of the face in both views.</p>

<p>Your manual should have a diagram showing the circle covered by the spot meter. It's not a "spot." Even though on many cameras it is less than 3% of the field, it is usually still not a tiny circle. If changing lenses changes the light within that circle, your metering will change. </p>

<p>I don't think it's possible to spot meter w/ an 18mm lens, is it? Or, to put it differently, it doesn't sound as if it would work so well, since w/ such a wide lens, unless you're on top of your subject, spot metering would only let a small fraction of your photo be properly exposed if it were a backlit situation. Up close w/ an 18mm lens, if you're shooting people, is going to be distortion city.</p>

<p>I love cameras that have spot meters because I don't have to go in close to get a reading, I can do it from afar. But even when using a hand held meter, I can meter off something close to me that has the same value as my subject, and let the background that's backlit be blown out because I want my subject to be exposed properly.</p>

<p>I think you do have both lenses. Just try them out and you will see. That is the fastest way and also most convincing way to you.</p>

<p>With a backlit subject, unless your camera's spot meter is very tight, it may "see" some of the background if you use a wide angle lens. As long as you are close enough to the subject that the face (or whatever you want to meter from) is larger than the area seen by the meter, you are fine.</p>

<p>Remember that the spot meter "places" the area it sees at "middle gray", which is quite dark. You need to compensate by how far above (or below!) middle gray you want the subject's face to be rendered. For a generic portrait of a Caucasian, that would be at least 1 stop, maybe 1.5 or 2 stops plus compensation. For backlit portrait, you may actually want the subject to apear quite dark, so no compensation or even -1 compensation might work. Depends on how you want the subject rendered.</p>

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<p>The principle is the same regardless of the lens. You want the spot meter to read just the subject. If the subject is very small, the spot meter my also read the area around the subject which could affect the reading.</p>

<p>It doesn't matter, <em>assuming that what's under the "spot" doesn't include the background.</em></p>

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<p>The spot covers a larger area of the person when you use the wide angle lens</p>

 

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<p>No it doesn't, BeBu - the spot covers exactly the same proportion <em>of the frame </em>regardless of the lens used. </p>

<p> A wider lens frames the subject differently and it will most often be the case that the main subject covers a smaller proportion of the frame with a wider lens. It is therefore more likely that a spot meter will gather data from outside the main subject with a wider lens. </p>

<p>The only exception would be where the subject covered the spot metering area entirely with both lenses- unlikely in this case I'd suggest. Just because the area spotmetered varies with the area of the frame (3.5% for me) does not mean that it will read the same area on the ground. If you want, test this simply with a zoom lens. Start at the longest end, and find a subject which just fills the spot-metering circle. Then zoom out, and see what happens to the subject/spot-metering circle relationship .</p>

<p>The OP will normally reduce risk by metering at a longer focal length because it more easily allows you to ensure that you're only metering from your desired subject.</p>

<p>And yes, the way you have phrased the question, it will matter- or at least it will matter quite a lot of the time. But you then have to recognise that with a spot meter what you do with that information is very important, and taking a single reading and slamming that value into your camera might not give the best result. For example having the face exposed perfectly might not help if the price for achieving that is a background so bright that you find it overpoweringly distracting. You might sometimes get a better picture by metering a little of the background with the person and so getting a picture that is a little darker overall. </p>

 

<p> A wider lens frames the subject differently and it will most often be the case that the main subject covers a smaller proportion of the frame with a wider lens. It is therefore more likely that a spot meter will gather data from outside the main subject with a wider lens. </p>

<p>The only exception would be where the subject covered the spot metering area entirely with both lenses- unlikely in this case I'd suggest. Just because the area spotmetered varies with the area of the frame (3.5% for me) does not mean that it will read the same area on the ground. If you want, test this simply with a zoom lens. Start at the longest end, and find a subject which just fills the spot-metering circle. Then zoom out, and see what happens to the subject/spot-metering circle relationship .</p>

<p>The OP will normally reduce risk by metering at a longer focal length because it more easily allows you to ensure that you're only metering from your desired subject.</p>

<p>And yes, the way you have phrased the question, it will matter- or at least it will matter quite a lot of the time. But you then have to recognise that with a spot meter what you do with that information is very important, and taking a single reading and slamming that value into your camera might not give the best result. For example having the face exposed perfectly might not help if the price for achieving that is a background so bright that you find it overpoweringly distracting. You might sometimes get a better picture by metering a little of the background with the person and so getting a picture that is a little darker overall. </p>

 

<blockquote>

<p>A wider lens frames the subject differently and it will most often be the case that the main subject covers a smaller proportion of the frame with a wider lens</p>

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<p>But that assumes that "small in the frame" is an inherent function of using a WA lens, <a href=" it's not</a>.<br /> <br /> (<a href=" ).<br /> <br /> In any given situation, regardless of lens, the subject is as big in the frame as it is: God knows, the birds I photograph are often small enough in the frame with 600 mm of focal length.</p>

<p> </p>

<p>It assumes nothing that the OP doesn't ask us to assume, for example standing in the same place. </p>

<p>And in any case my contention is not "small" it is "smaller". I don't think its possible to debate that a wider angle lens will make a subject smaller in a full frame than a longer lens at the same format. I don't need to make any contention about the<em> absolute</em> size of the subject in the picture, only the <em>relative</em> sizes with increased or reduced focal lengths. The test I referred to above makes it quite obvious I think. </p>

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<p>and it will most often be the case that the main subject covers a smaller proportion of the frame</p>

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<p>I think that qualifies as an assumption, David.</p>

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<p>No it doesn't, BeBu - the spot covers exactly the same proportion <em>of the frame </em>regardless of the lens used.</p>

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<p>Yes the same proportion of the frame but the OP said that he/she doesn't recompose and stand at exactly the same spot so with the wide angle the subject must be smaller and the spot is larger in relation to the subject. </p>

<p>And since the OP stand at the same spot, if he/she used a handheld spot meter then the reading is identical but when using the camera spot mode it would give different readings.</p>

<blockquote>

<p>Will it matter if I spot meter a portrait face with 100mm telephoto lens vs 18mm wide angle lens.<br />Just to clarify, <strong><em>I am not recomposing my shot. </em></strong>I am <strong><em>standing at same spot and using above two lenses with spot metering in both scenarios.</em></strong></p>

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<p>IF you are using the Spot Meter in your camera’s TTL metering system –<br /> YES it WILL, very likely will give you a very different exposure reading.</p>

<p>For example:<br /> IF one uses a 100mm lens and composes an HEAD & SHOULDERS Portrait and one Spot Meters the skin tones of the face, approximately the area of a CHEEK will be read.<br /> IF one stands the SAME PLACE and then uses an 18mm lens – the Spot Meter will over the whole Head, part of the Torso and a goodly amount of the BRIGHT ’back lighting’.</p>

<p>***</p>

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<p>Besides this question if anyone has expert advice on backlit portraits I am all ears&eyes now. Thanks as always.</p>

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<p>As a beginning guide using AVAILBLE LIGHT ONLY - IF you want to use the Camera’s TTL Spot Metering: then meter the shadow side of the face (or other shadow skin tone) and open up about one stop for Caucasian Skin:<br /> <img src="http://d6d2h4gfvy8t8.cloudfront.net/12965374-md.jpg" alt="" width="486" height="680" /></p>

<p>Then shoot a lot and learn by mistakes.</p>

<p>If you want to use a wide lens (and it is not a zoom) then move in close to make the Spot Meter Reading and then recompose the shot.<br /> If you want to use a wide lens and it is a zoom lens, then make you Spot Meter Reading using the telephoto setting and then zoom out to the required Focal Length.</p>

<p>WW</p>

<p>Thank You All</p>