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Histogram

Alright, next up is the histogram. The histogram is very important for judging and making sure that you have got the right exposure. So, when you play back an image after you've taken it what you wanna look for is an information button, info, or a display button on your camera, or perhaps something else, it depends on the camera you have, that allows you to see this little graph. This is a graph with a tonal distribution. It's gonna tell you if your picture is too light or too dark, alright? So, what this graph is is it's showing you all the pixels. So, we have white pixels, we have black pixels, and we have all these different shades of gray, and for the moment, we're gonna forget about color. Alright? So, we have a picture that's composed of a lot of different pixels and in the histogram what we're gonna do is we're gonna organize all these pixels. So, in the very left column are black pixels and then ones that are really near black. And then over to the right hand side (clears throa...

t) where we put a white pixel. And so, now we have a graph where we can see, oh, okay, we've got a whole bunch of middle gray pixels and a few dark ones and a few light ones. And it's very very easy to see if you've got the right exposure just by the shape of the histogram. So, a histogram might look a little something like this. So, this vertical height is measuring the number of pixels at any one brightness level and then it's broken up from left to right going from darks, shadows, mid-tones to highlights. And so, you can easily see if there's a lot of pixels in one particular group. And so, this has a lot of pixels in the mid-tones, which is where a lot of normal pictures are going to be. (clears throat) Now, one thing you wanna keep an eye on is the leftmost column 'cause those are pure black pixels, which means that you have got, essentially, no light into those pixels. And so, if there's a lot of them that are stacked up really high in that left hand column, you've got a really dark photo. I'm not sayin' it's bad, you've got a really dark photo and you may need to take a look and judge if that's appropriate for what you're shooting. Same thing goes with the right side of the graph is those are the white pixels. If you have a lot of white pixels, those are gonna be blown out pixels without any color, without any detailed information, and that's probably not a good thing in most photographs. It really is something that you have to look at on an individual basis and so we'll be looking at a bunch of different photos in here. Many cameras will have two different options on graphs. You could either choose a brightness one, which is just all the pixels combined together, which is a good way of judging the overall brightness, and then there's RGB histograms, which separate it out into red, green, and blue pixels so you know how bright any one particular channel is. I find the RBG histogram a little bit easier to read, I like the colors and it can tell you if you're getting a really bright area in one of the colors where you may get some clipping on that. Now, this is really handy to have on a digital camera, especially a non-mirrorless style because when you look at the back of the camera under bright light or even just normal outdoor light, it's hard to judge is that the right exposure or not because it's being influenced by the light hitting the LCD on the screen. If you have a mirrorless camera, you are at a little bit of an advantage because you can hold the EVF up to your eyes, block out all that extra light, and get a better view of what that final image is gonna look like. But the histogram is... I think it's like the lie detector test for pictures. Did you or did you not get the right exposure? And this will let you know that you got the right exposure. Generally, what you're worried about is a big mound of information over to the right hand side for over exposure and big mound over to the left hand side for under exposure. But you should not just assume things with histograms. Every photograph is gonna have a different looking histogram, and so I encourage you to playback your images, look at your histograms, and start learning about what's going on in those photographs. And so, we're gonna have an impromptu quiz here on this one, and so, what team are we next up with, A or B? Does anyone recall who the last question was with? And so, for team A the question is is what's this histogram gonna look like? You have any sort of ideas on what this histogram is gonna look like? Just give me a general idea of what you think it looks like. It's gonna be the big spike on the right hand side. A big spike on the right hand side. And we indeed have that. So, that's worth a point, I think. And so, there is a big spike on the right hand side because we're photographing snow. Snow is light and in this case we do have a big pike up here. And just in case you're wondering, this other little mound of information in here, what do you think that is? Anybody wanna just call it out? The sky. The sky, yeah. That's the sky and you'll also see the blue channel's a little bit brighter there, so you can see that actually sticking out there. Okay, we're gonna go over to team B and we're gonna do the reverse. Here's the histogram, you tell me what we're photographing. Just tell me what you think the photograph looks like. (laughter) So, this is either underexposed or just very dark like a night sky. Right, right. Okay, so is it a very dark photograph? It's a dark photograph, it's from nighttime. So, they get a point too. That was kind of a free bonus point for everybody there. Didn't do anybody good, did it? You wanna be able to look at photographs, guess what the histogram is gonna look like, look at a histogram and guess what the photograph is like. Alright, so when I'm photographing this and I'm looking at the photo and I'm thinking, hm, is this the right exposure or not? I can't tell, I would like more information. Let's look at the histogram. Oh, we've got a lot of information way over on the right hand side. Let's try darkening this photo up and so, now we can see a lot more color information in the sky. And so, this is just a really useful tool for knowing if you got the right exposure. Alright, one of the things I just told you moments ago was be aware of spikes on the far right hand side. In this case, we do have a definite spike on the far right hand side, but in this case I don't care about the spike on the right hand side because it's a cloudy day, it's one of those overcast days that has no texture in the sky at all and it's the subject in the middle of the frame that's most important. Now, some of your cameras will have blinkies and these are things that you can turn on and off that show you the highlight clipping of pixels that have become overexposed, and this can be very helpful. For instance, for a wedding photographer, if the bride's dress is completely blinking, you have no detail in it. She's probably gonna be mad. You better change your exposure so that you can see some detail in those highlight areas. Now, a word for those more advanced users. This is a histogram that you see in your camera, it's of the jpeg preview of your image. It's not the actual raw image. So, it's quite possible you could get these blinky highlights turning on, telling you, oh no, the world's gonna end, but in reality, on your raw image you actually do have all that information. And so, it's kind of a precautionary warning that comes on a little bit sooner than it actually needs to come on if you are shooting in raw. If you are shooting in jpeg, it comes on right about when you need it. So, when you're judging the exposure of a picture that you've just taken, there's a number of things that you can look at. You can look at the back of the camera, you can look at the histogram, you can look at the light meter, you look at the scene with your own eyes and you're like a private detective who's trying to figure out what's going on in this mystery. But, you have different pieces of evidence and so, you need to be looking at all these pieces of evidence to see if they match up 'cause I can't tell you this is a bad histogram because it might be appropriate for a certain type of photograph. This is a tricky situation. I have a very dark subject and a very light background and I am really stretching the range that my camera can handle because there's important information over on the left and some pretty important information over on the right. Now, when it comes to the histogram and exposure I can move left and I can move right, but I can't stretch things out or squeeze things, okay? That's not possible. And so, we can change our exposure and make it brighter or darker, but we can't do both at the same time. And so, that gets to be very tricky when we are in high dynamic situations, where we have very bright lights, highlights with clouds and waves, and then we have very dark shadows. And so, we have dark areas and we have light areas and if you're asking, but John, how do I make a better photo? Come back at a different time when the light is better. This is why photographing in the middle of the day can be very very difficult. And so, be aware that if you're getting extremes, there's only so much you can do with your camera and there are limitations and there's always gonna be... I mean, the cameras have been getting better and better and I'll talk about some of the best cameras when it comes to dynamic range here, but there are just limitations of brightness levels. Really bright and really dark at the same time is very challenging for cameras. Now, as many of you know, I'm a big fan of visuals. I love visuals and I like colors, I like to be able to see things, I think this is a really fun looking histogram and it's an equally fun photograph that goes with it. So, compare your histograms, look at your photographs. I think this is kind of an unusual histogram here. Does anyone know what's goin' on here? Does anyone want to throw out a guess as to what's goin on in this photograph? There's something.... (audience member mumbles) (laughter) There was, what was that? A clown by the ocean. A clown by the ocean. (laughter) And so, one of the things is that you'll see these color channels really spiking when there is a noticeable color. What color is really noticeable in this photograph? (audience mumbles) Red and green combine to form yellow. Oh. That was an aha moment right there (laughs). And, you know what, I was... When I make this class, I go through all of my photographs and I'm looking for examples of this and that. And so, I was working on this section, I'm like, okay, I need some good photos that show an interesting histogram. And so, I had this weird photo of an LED hula hoop and I'm like, okay, this is gonna be a cool histogram. And I pull it up and I'm like, it's not really that interesting. And so, it does not necessarily correlated between the photo and the histogram. I think this is a pretty interesting histogram right here. There's something weird going on here and I'm not even gonna ask you because I would never guess this myself. But, here's what's going on is that there's a lot of different colors and there's just slightly different brightnesses of that one color according to where it is. And so, I think it's intriguing because you start learning about your photographs when you study the histograms. I've been using this one in my class for many years. This is, I think what I think is, you know, traditionally thought of as a terrible looking histogram. Spikes on both ends. That's like the worst case scenario in a photograph, so you must have a terrible photograph. Not necessarily. Wow. Things start to make sense when you see both ends of the histogram and the photograph. And so, hopefully that makes a lot more sense for you now.