Alright, up to this point we've been talking about the individual components in photography. And now we're gonna start mixing them together and getting this all together in one photograph. First up we're going to be looking at the metering system in the camera, how it reads the light entering through the lens. So what photographers really want to know is how much light is striking their subject. And, the way that we used to do this is with a hand-held light meter. And they still sell these and they're still very valuable. Because what you would do with a hand-held light meter is you would go up to your subject, you would press the little magic button on it and you would get the exact reading of the light hitting that subject and it would give you a recommendation ISO, shutter speed and aperture. And if you set that, you will get the perfect exposure. And so if you want perfect exposures every time, you go out and you buy one of these light meters. And you quickly find out that when you...
want to take a picture of that mountain way off in the distance. Its a long walk to go up there and get the light reading and then come back. So this isn't the most convenient thing in the world, but its very accurate. What your camera has in it is a light meter as well, but this is a reflected light meter which measures the light reflecting off of the subject. And now we're measuring two different aspects, we're measuring the brightness of the light and the brightness of the subject. And this is where there are a few problems that you need to be aware of and be ready for. The camera's light meter is assuming that everything you shoot a photograph of is middle-gray. Its this 18% gray, this average of light and dark. And if your subject is, in the middle tone of this gray, then your camera is going to read the light correctly and recommend the proper shutter speeds and apertures for you. Where things get a little bit tricky is when your subject is either lighter or darker than that middle tone gray. Cause what happens is less light gets back to the camera and the light meter says, whoa, we're not having any light coming in, what's going on here? Must be really dark, there must not be any light at all. It doesn't know the difference between a dark subject and a dark light. It doesn't understand that aspect. All it understands is what's coming into the camera. And so the camera says, wait a minute, we don't like dark things. We better recommend a shutter speed, an aperture that lightens up the subject. And so what's gonna happen, is its gonna try to over-lighten dark subjects. It doesn't like dark subjects and so you have to be able to go in and understand this to correct for this. Now the same thing is going to happen with very light-colored subjects. Its going to reflect a lot of light back to the camera. The camera is gonna go, oh my gosh, look at all this light coming in here. We better recommend a different set of shutter speeds and apertures so that we make this middle tone gray. Cause the camera thinks everything in the world is middle tone gray. And what its gonna do is its gonna end up darkening everything in the photograph, even though it doesn't really need to. And so you, just with your own eyes, are going to be able to easily decipher this information. And so you're gonna need to guide the camera a little bit in those unusual situations of very dark and very, very light situations. And that's just because our cameras have reflected light-meters. It doesn't know everything going on about it around it. Now, in your camera is going to be an indicator which lets you know what the camera is thinking, what its reading in its light. Many cameras have what's called a graphic light meter, which is a little bar or needle that goes from side to side or up and down. And it might show you minus two, or in this case, one stop over-exposed, which means its going to be too bright. And under normal situations you want to make sure that its in the middle. Some cameras have a numeric light meter system which just uses a number. This would be two stops under-exposed, or it might be a stop over-exposed. Or many different increments in-between. So you'll have to see how your camera reads that sort of information and displays it to you. Normally, with the numeric one you want to try to get it to zero, at least as a starting photograph, you might say. Now the way the camera reads light is through its metering system. And traditional cameras had a center-weighted metering system which read most of the light in the middle of the frame. And this was pretty good if your subject was in the middle and it wasn't too bright and it wasn't too dark. Its got a nice little averaging system. But photographers wanted something more precise. For instance, you're photographing a bird and there's a lot of white sky around it, you don't want that metering of the sky. Its the bird that you want to meter. And so many cameras these days will offer some sort of spot-metering system. And it can be very, very accurate. And back in the days of film photography, this was really important. We'd spend the next hour talking about spot-metering cause its a really valuable tool. But in the days of digital, its not that hard to shoot a photo and see how you're doing. But there is a new metering system, and I call it multi-segment metering system. Some cameras call it evaluative, or matrix-metering or something else. And what this is, is its measuring the entire area in little boxes and each of these is a spot-metering box, you might say. And it measures the light in that box and it compares it with all the other boxes and it comes up with an average for the entire scene. In real life this does an amazing job. Its really accurate and this is what most photographers use because it is so accurate so much of the time. It can be fooled, if subjects are too dark or too bright. But in a general sense, its a very good system to use for most people in most general photography. So its what I recommend in most cases. With our digital cameras, we can now judge the brightness of our photographs using not only just the display on the back of the camera, but something else called the histogram. And so the histogram can be brought up by pressing the info or display button on your camera. It could be a slightly different button. All the digital cameras have it, you just need to figure out how your camera does it. And what this does is it shows you a graph of the tonal distribution of the image. And this is gonna be great because you can judge very quickly and accurately whether your image is too bright or too dark. The way this graph works is, imagine the pixels that you were photographing, and they range anywhere from pure white to pure black and we're gonna forget about color right now. And so what the graph is, is its the black pixel on the far left and every tone of gray pixels all in a line-up stacked on top of each other as we get lighter and lighter and we put the whitest pixel over on the right hand side. And so its basically a mound of information with dark on the left and bright on the right hand side. And so, a histogram might look something like this. Now this is a very good-looking histogram in my opinion. And so what we have vertically is the number of pixels, relatively, relative number of pixels, that are any particular brightness. Over on the far left are the dark pixels, the shadows, the main mid-tones and then the highlights over on the right hand side. Now what I particularly like about this histogram here is over on the far left hand side, is that there are no pixels in the pure black column. And if I have a pixel that is pure black there's really not much I can do with it. I can't lighten it up, cause the camera, the sensor, that information about what color its supposed to become, isn't there. I can take a pixel that is almost black and I can make it black. And the same is true over on the right hand side, which are the pure white pixels. If something is pure white and I try to darken it, it doesn't know which color to become. And so its not going to look right if I try to adjust it. And so what we're trying to do, is we're trying to capture the darkest and the lightest information. And so if these lines against the wall are empty. You've captured the brightest and the darkest tone in the photograph. And that's great, because then you'll be able to adjust or manipulate that later in Photoshop, Lightroom or whatever program you want to use. So, this very nice looking histogram is for a wild tiger in India. And this is nice to see because if you're out in the field checking photographs, sometimes its hard to get a good view of the LCD on the back screen of the camera. Where it might show it to you as being too bright, but you're not going to be able to see that. But if you look at the graph, that's a shape. Shapes are very, very easy to read. And this tells you that that picture is very, very bright. This one tells you its very, very dark. We can actually go on and on about histograms for quite some time but we're gonna keep it short and simple here. If its too far stacked to the left, its too dark. If its too far to the right, its too bright. And so what you're trying to look for is a healthy mound of information in the middle that kind of tapers down to the edge. Every situation is a little bit different and will have its own unique histogram. But if you look at the histogram, and its mostly in the middle of the frame, despite what anything else looks like on your camera, you can walk away feeling confident that you got a good exposure that you're going to be able to work with later on. And that's your main goal out in the field is to try to get it as close as possible in most situations.