Lessons

Lesson Info

Understanding Histograms

All right, well, what we want to do next is we're going to dive in a little bit more into this we're gonna talk about history grams because these two things go hand in hand right? We've talked about the direction of light how we can affect contrast we could make things brighter and darker by moving that around we've talked about dynamic range you know what we're gonna do is we're gonna talk about history rams so I'm gonna do is I'm actually going to change the subject a bit I have here this is a digital calibration target and what it does is it's a calibrated middle gray and black and white and so what I want to do is I want to be able to demonstrate how a hist a gram how to read a history so here's what I want so students put your stuff down students come out here I need it to use you as an example ok all right so here you'd be right here just make a line right here, okay? Make a line we're gonna make a actual gonna make an actual graph here all right? I'll go with me on this hang out...

with me let's say that these guys are in a class that I'm actually teaching and it's maybe a high school class okay and at the end of the course hey paul, you gettin a good student? He gets in a copier remember your grades di gets a d a c a f okay all right so we have this distribution of grades across right now I want to make a chart I want to say here are the grades that we have so all the people that got a's come over right here many people that got a's here you stand in a room just like this one two three okay anybody got a b no bees how it sees see right here he's got a d and an f sorry, but here's, what happened? You turn in your paper late I found it so now you're gonna have a seat. Okay, wait do that. Okay, now what we have hopefully you could see this from the overhead we have a human graph of our classes distribution of grades so we have three people that have a cz nobody got to be we have to seize we have one d and we have no f right that's the distribution now you guys can go sit down put that in your brain you're thinking what does that have to do with history rams I'm so confused a history graham all history ram is is it's the same thing as charging out how many people got grades in the class it's taking your photo and it says I'm gonna look at all the different pixels in that photo all the dots and everybody that is an absolute black dot come over here and line up on the chart okay, all the black dots are gonna line up and then everybody that's not quite black with just a little bit more gray line up all the way over to hey, I am totally white I'm over here actually from the camera I think I did it backwards yeah, all the black dots over here and all that right down through here and it's showing the distribution of how many black pixels do we have? How many middle grey pixels do we have and how many white pictures to be half and everything in between now depending on your camera's gonna have millions of those right? So it's gonna actually chart this little graph now what you have heard maybe which is totally not true because there are good history rams and bad history grams that is not true. Um there are history grams that help you understand your exposure and that's all there is so sort of like a thermometer there's none like good temperature and bad temperature there's just temperature and you can judge for yourself if one hundred fifteen degrees in phoenix is too hot, which it is that's why we're here or any degrees and no seattle is ok so we're going to hear is I'm actually gonna tether thanks, kelsey we're tethering this to my uh light room and I'm a zip over to the light room awesome thank you alright when we have a light room up here by the way I've been running lion for about a month now no problems it's awesome. So if you're thinking about upgrading on your mac do it so I do is I'm going to start my tether is this not a turn on? Yes. Okay, so I wanna start my tether history. Graham good. This is asking the phone import, which we don't we want to use the stuff that's brand new. Now what I'm going to do here is going to leave this bar out here just for a second so you can see what settings I'm using and then we'll move on. So if you add some light, they're forming soft. Yes. So I've done this intentionally where we have black, middle grey white so that you're absolutely clear that the blacks are gonna goto left in the white's gonna go the right and has absolutely no correlation toward the blacks are on the actual scene just like when we correlated grades it doesn't matter where the students air sitting we graph it out all the age where are we going to go in the same place all the bees are all using the same place so the history graham isn't correlated tio what this looks like um so here's what we're gonna do when I put my camera in just normal aperture priority mood I'm gonna crank it down teo I don't know three two we'll crank my eyes so up to something like oh, eight hundred just to give us a little bit of breathing room here and then I'm gonna do here to make sure I can get a good picture of this. All right? So I'm just gonna take a shot of the whole thing. Wait a minute. Thanks. All right, I'm gonna hide this little window there right now, the first thing you'll see is that my color temperatures way off that's okay, I'm gonna go into the develop module. It doesn't matter if you don't know what I'm doing in light room it's not a light room tutorial we really care about is this thing over here that's the history graham this is really what we care about now this is something you probably see. You've got yellow and you get green and you've got red. You got all this stuff in here that's because this is a color photo and this is a color history graham and there's different types of history rams so the one that's on the back your camera more than likely isn't a color history ram this is showing us is plotting out on this system graham where the different color channels are falling we haven't gotten a color yet so don't worry too much about that what I'm gonna do too uh really helped clarify this I'm gonna go into my develop module and I'm going instantly I'm just gonna make that black and white we just care about luminosity this point okay, so let's just subtract the color now it's happening here as you can see that the blacks are on the left hand side we've got this middle gray area we've got a little bit of white when the question is what the heck this should be way over on the right hand side if that's actually white that's true that means that this is under exposed a little bit because this should be white but on our history ram is showing that it's just very light grey so what we can do is we can go in here and we can say okay I need to fix some things so I could use exposure compensation or some other things to figure that out so I want to actually go in here and put this on uh manual mode so I can die a listen exactly where we want it to be zipping this down okay, I'm over exposed this by about two thirds of the stuff, okay? We're gonna get a new picture coming in here in a second all right again is that nash see color I'm going just make that black and white and you can see I'm sorry I underexposed I did the opposite s so I moved it from the lights here too the lights coming down here and you can see that this history graham is giving us a guide to tell us if our exposure is correct or not because probably if we looked on the back of the camera to our eyes it would look right well, okay that's a good exposure but we could look at the history graham right off the bat and say the whites aren't white it's under exposed something going here improve that so I'll go here and over exposed by stop is going to pop in here. Okay, there it is this black and white now look how that's shifted so this is shifting first exposure there's our whites second exposure are whites went down third exposure white's back up there so zoom in there really closely. You can see that first exposure there's the whites second exposure when under exposed, the white shifted down and everything else did third exposure whites are shifting up also noticed something. We have our blacks all way here and we have room on each side of this sistah graham meaning to get this absolutely black and absolutely white you can't do that in the camera you could tweak this and do all kinds of settings, but you've got to go into post production and you've got to do some manipulation to get your blacks absolutely black and whites absolute the white so the most controversial statement of all maybe today is I do not believe in the statement you have to get it right in the camera I believe in the statement you have to do the best you possibly can to shoot everything appropriately to do what you can to get it right the camera but there's always post production, especially in commercial photography there's not just a little bit of postproduction there's a heavy, heavy duty post production and so release yourself from the expectation that you're going to get it right in the camera. The guys I have to get it right in the camera or photo journalists, they have to shoot it, they've got to get it dialed in and then they have to get it to the agency and it goes live, but for commercial photographers, you're not going to get it right in the camera. You've got to get it to your team so they can do postproduction the colors have to match, they're gonna tweak it there is no ad that I know of that was shot right in the camera correctly in the camera, so please beat me up online for that one yes we have a question online. We do have a question online from yamamoto dole. Can you please explain the difference between a normal hissed a gram and an rgb history? Graham especially if the normal history ram is an average of rgb values or not. Yeah. So, um yes. So if we go back here, we're gonna go back to the history ram I love these questions are awesome. I'll put it back into color. So, um, much of this is gonna be answered when we get to our color theory, uh, section which can't that's gonna be so awesome. So color travels in in three different colors, right? We have red, green, blue and as it comes through the lens and hits the sensor there's all kinds of stuff that happens. But the distribution of all the red darks, mid tones and whites and all the green darks, mid tones and whites and all the bloom interns, they're not the same. So you could have more shadows that are blue, then red. And so what? This helps us understand. In fact, you can see here. Blue is usually the guy that's that's out of whack. If I, uh, if I zoom in here you can see we have and also we have these colors that are you'll have to wait to the color part to understand this but you could see where the colors mix, we get new colors but what this is happening is it showing that the blues in this because our color temperature is off we didn't do the correct color temperature the blues are shifted way down into the shadows we have more blue in the shadows than we have red or green so that helps us understand if we have color shift in our photos so we can look at this and we have a mathematical graph that says we have too much blue here we need to add you know, we have our blue has shifted too far to the left side of the history graham it's underexposed we need to shift that we could fix that by changing our color temperature so watch this scene I'm shifting those things, getting them into alignment now they're all aligned now let's guess what's gonna happen to remember we had that nasty orange picture that was all disgusting. I didn't do a color temperature fix here I just shifted the history ram based on I shifted the color temperature based on the history ma'am now when we come out it's almost color corrected pretty wacky, huh? So what we're doing here is with those color shifts we can see if we have something out of whack specifically with our color and we did and by shifting our color temperature all of that stuff line back up and this came almost exactly into what we would need it to be so I'll do an actual yeah almost no difference so those that's what the rgb history game is doing is it showing that we have a shift in the color in a way that we don't want now if I wanted this to be really super super blue, notice how my blues air now shifting to the right there more highly exposed and I've got this blue tent that stuff that you can't see in the back of the camera a lot of times when you're shooting but you can open up a history graham and see that immediately it's really cool moron color to come I just guarantee you're gonna like the color stuff all right? Any questions from you guys? Yes mr josh medium format camera could you get the, uh highlights and shadows more camera better? Absolutely. Yes, yes, very much so and also a shooting raw it's gonna help you with that? Because the way that the distribution of uh, light across is not linear in other words, you don't have equal amount of the darks equal amount of mids an equal amount of whites it's not a linear distribution so what happens is when you shoot raw you get still a nonlinear distribution so you have a lot more detail in the whites than you do in the shadows I'm still doing this backwards right? This is whites over here yeah white lots more distribution and so what you can do is if you shoot raw you I think it's two thousand forty eight levels of actual white that you can bring in and detail of stuff if you're shooting at a higher bit rate you haven't even mohr information so medium format camera helps you a dynamic range in ways that are hard to describe but easy to see so when you get into post production you've got just like a sea of information to play with your shooting and small j pick which is what we have this hooked up to right now you lose all of that information are not all a lot of yes sir changing the, um exposure time conditional cameras um I was working with the gamma would be is it the same thing as uh film from way back when we're the gamma you would have a certain gama and then you end up having certain colors depending on what the exposure time is so that if you change your s o and you changed your f stop but then you change the exposure time you could change the part where you are in your gamma the gamma I think it's going to be your assistant to your camera where you're changing your gamma is in post production and so um and I'm not qualified to really talk about how gamma changes I don't know, I know that gamut uh there's gamma center point here there's gamma here there's a game on output yeah, but I don't know enough about it to say oh it's two point eight years d sixty whatever that is so what I would do theirs they are experts like the x right guys brenda hip shirt who is filled right now I've got these guys that called me up all the time it's a mark on this video actually you said this and this but I've got these guys not me color theory of the past few years they would be the guys that would know that and x right photo has a wealth of information about that specific stuff I'm just not geeky enough and I'm not good enough math tio no it so thank you. I'm bad at math I don't know my multiplication tables just me six times six no idea, no idea. Okay, um hissed a gram's. Any other questions at for history? Grams from the live audience have a question from bobbin vashti who would like to know if you could explain a little on how white balance affects the history ma'am um white balance doesn't affect the history unnecessarily it effects the color history graham as we just shot it will affect the shift if I goto to black and white so this shift right here see how that shifting around now zoom in on this so well I'll zoom in this we'll do this a couple more times somebody on the live audience can see this so the thinking is oh my gosh everything is shifting around why is that why is the exposure changing well when you're shifting your color temperature what you're doing is you're changing your distribution of colors across the scene and so that's really what shifting so it's not right for me to say it doesn't affect the history ram effects is how the colors were distributed and that does affect history so I hope that that claire do you think that's a clear answer okay so is the shift in the distribution of colors is changing and therefore you're changing your exposure yes and one more quick question that a couple of people have asked both courtney and one credo photography is the hiss graham being contaminated by the ambient light yes I thought it should be three sharp up and down spikes uh that leads into our next demonstration yes so the question is if this is calibrated black grey and white why isn't it eh a spike should be spike right? Nan you missed a graham where's my mike all right. Well, let me explain that I'm gonna go over here zoom this out sorry. Um if we look closely I'm gonna crop this image you have to release this custom crop this image here on lock so again, I will crop this image probably the image what I say feeling with reckless abandon something like that. Okay, so I'm just gonna get the black in here just black, right? I'll kick out these panels here and if you look closely at that you can see that this light this light is coming from one direction it's coming from the left what did we learn about the direction of light? The direction of light directly corresponds with contrast. Now there is more light hitting this side on this other way there's more light hitting the left side of this black panel, then hitting the right side of this black panel and that means that this side of the black is less black than this side of the black. And so there is not one consistent black and so within this class let's say this is first period english class and we're surveying all the different pixels here all the different students we still have a distribution of grades if you will across the black used to have this is a lighter black than this and so that's what happens over here on the panel the blacks are showing up not as a spike but as black little bit lighter black little bit lighter black little bit lighter black and the same thing is true if we zoomed in on this the only way to get that to be a spike is for us to get this light to a line exactly center so that this is exactly evenly lit so that there's a difference in the dark to the light and they're probably have to be much higher tolerance is this would have to be absolutely calibrated to the blackstone exactly black et cetera so you're not going to see a spike uh usually the other thing I need to show you them we still need teo talk about history grams a little bit more there's another little demo I want to do so I'm gonna bring my camera over here. What I wanna do is next what's going to get a little wedge here so when I need to make sure that I'm still tethered yep okay show you a couple more things here. All right? So I'm gonna zoom in quite a bit here see if I can do this it doesn't matter if this is in focus or not all we care about is the color so this is just yeah, the black area there there it is. All right I'm gonna convert this to black and white just to avoid confusion here and again that's that's the distribution of black we don't have just one solid black we have a bunch of different lex now I want to do something else here I'm gonna turn my camera on tio aperture priority mode and I'm gonna shift like camera, okay? I just shot just the black a little bit and just some gray just a little bit. All right, do you see the big huge problem here now this has to do with how tt almeida ring has all kinds of issues but he's trying to average everything out degree it's over exposed everything but uh now that we know about history grams we can look in here and we can see a couple of things. This is much more like a spike. Now the reason is much more like a spike is that we have a lot less of the gray in there so we don't have as many students in class getting seas only have a couple. So you're seeing that a lot more black in this so we're seeing a lot larger distribution of black and for this we have to take our exposure to fix this take it back down to get back down ticket back down there, ugo and now black is black and gray is grey as it should be sorry instagram is just a guy I was just telling us hey, this is right. This is not right. I mean, we can sort of understand that.