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Thanks Kent & Scott.. So main point is too much foreground with horizon here caused metering confusion/over exposure?
Classicly having a scene with such an intense bright spot such as the sun in the scene, a strong specular highlight reflecting the sun or a scene with large expanse of bright white (snow, wedding dress, etc.) will "fool" the meter into using an exposure that creates an underexposed image.
This is a bit of a misnomer to say "fool" the meter, because the (reflective) meter ... by design/intent ... is providing you an exposure recommendation that will yield a "middle gray". If we take this scene and desaturate it 100%, then apply Blur>Average to the entire scene will will get a solid gray value of 128. In this case, we can see that the meter was not actually "fooled", but it intentionally set the exposure to render the scene to an average middle gray. In other words, it did its job as it was designed to do and it wasn't "fooled" at all. We are the ones that got "fooled", in that we forgot to tell the camera that we don't want a "middle gray" exposure value for this scene ... we want one brighter than middle gray.
Our camera has know way of knowing if the subject that we are shooting is supposed to be black, white or somewhere in between. Thus, it was designed to ASSUME that most scenes are a mixture of values that typically will average out to around middle gray, so that is the value it is based upon to give us. If we point our camera (reflective metering) at three different sheets of black, gray & white construction paper and take three picture using the camera's reflective metering ... the camera's (reflective) metering will give us three different shutter/aperture recommendations. Yet, if we use those recommendations, all three images produced will be middle gray ... one underexposed, one overexposed and one properly exposed.
Because the camera doesn't know what it is looking at, we have to use our knowledge to provide of our subject/lighting to decide if we want to make an adjustment to the meter's recommendation. If we are looking at an "average" scene ... it can be a good recommendation to use. But, when we are shooting overly bright (or overly dark) subjects we need to make an adjustment for the fact that the (reflective) meter is going to provide us a recommendation for "middle gray". If we want our scene to be brighter than middle gray, we compensate by opening up. If we want our scene to be darker than middle gray, we compensate by stopping down.
Understanding that our (reflective) metering is designed to give us a "middle gray" is key to understanding when/why our exposures are "off". It is also key to understand how we can "control" our exposures to give us the creative liberty to move our exposures according to what our vision for a scene can be.
That being said ... it was in regard to "reflective" metering. There is also (not in camera) "incident" metering. The difference being that incident meters measure the amount of light "falling" onto the meter. Going back to our three sheets of construction paper. If we used an incident meter to determine how much light was falling on them, we would get the same reading for all three (assuming they are all using in the same lighting). This time, when we shoot them, we get one black, one white and one gray ... rather than three gray as before.
I know that this can sound confusing and counter-intuitive for some. I had trouble with it myself back in the day. So, I ran the test with the three sheets of construction paper using the camera's reflective meter ... and sure enough, I got back three identical gray slides. Ever since then, I ask myself, is this scene an "average" scene. That, and I picked up an incident meter to use. Also, when I find myself without (or not wanting to bother with) an incident meter ... Sunny 16 rule will put you close. Even if not exact, Sunny 16 can be more dependable than a reflective meter for some scenes.
In the case of this scene ...
Sunny 16 says that for clear daylight ... set your shutter speed to match your ISO, and set your aperture @ f16 (or equivalent shutter aperture combination). If we shot this scene at Sunny 16, we would be slightly underexposed because the clouds are veiling some of the light, so we would want to open up a little bit to f13 or f11. This should give us an exposure that will render our snow and clouds closer to white than the underexposed gray that the camera provided for us.
There isn't a lot that we can do to contend with the intense sun spot in a scene. The difference (dynamic range) between it as the brightest part of the scene and the darker parts of the scene can be too great for the camera to record both simultaneously. As such, we have to choose which part of the scene is most important for us. For me, the sun isn't the important part of the scene ... the snow and the tracks taking us to the people are.
Honestly though, this is one of the toughest scenes around to contend with using a reflective meter (i.e. in camera). An incident meter makes short order of it, and Sunny 16 gets you pretty close when you get it in your head how to read/adjust for it. Of course, you can always bracket your exposures from what your camera recommended. Some wedding photographers will go a +3 from the camera metering. I tend to go +2 1/2 as my expectation, but will also bridge that with a + 1 1/2 as a "safety shot". To me, anything less than a 1 stop bracket is a waste of a shutter click, PP can deal with a 1 stop variance easily enough ... thus Sunny 16 works quite well in today's digital realm once you get used to it. Of course, one can also, chimp for a test shot or two.
Much (too much maybe) to digest, but HTH.
Edited on Jan 16, 2013 at 03:49 PM · View previous versions