Law of Reflection

 

Understanding Light

 

Lesson Info

Law of Reflection

We're gonna talk about something that is called the law of reflection. And so, when we're talking about specular highlights and trying to control those, we need to understand this thing called the law of reflection. And we're gonna do this, if we have time, we have Lex. She's gonna wear some really awesome glasses, and we're gonna see if we can control these things. So, the way this works is when light comes from a direction and it hits a flat surface ... We're assuming that this is an absolutely flat surface. Let's say this comes in at a certain angle, and it's measured by this line right here. This is a 90 degree line to the flat surface. This is called the normal line. This right here is called the incident ray. So, this is light coming in. So, this light comes in at 36 degrees. It will always be reflected. So, this is called the reflected ray. It will always be reflected at the exact same angle. Always. And so, if this comes in at 36 degrees, it's going to be reflected at 36 degree...

s. And this is called the angle of reflection. The angle of incidence is what degree it's coming in according to the normal line, 36 degrees reflected at 36 degrees. And so, once you know that, on a flat surface, you know that if this light here is casting a highlight here, if you move this light to 50 degrees, the reflection is also gonna move to 50 degrees. So, if it was causing problems here when it was lower, you just move that light and both things will move And so, when you start having reflections on eye glasses and things like that, you just need to move the light and it will move the reflection as well. So, if the light is low, the reflection is gonna be low. Light is high, reflection is gonna be low. Right? Yeah, it's totally the opposite. The problem is if this is a convex or a concave or if it's got texture to it, then light doesn't just hit and reflect it hits and scatters. And that's where you get issues of really hard to control specular highlights. It's when it hits something that has a textured surface because there's a new law called the angle of refraction which there was no way I was gonna draw out that. But basically it hits and it scatters in a scientific way that's crazy. We don't need to understand it. But this will help us get there. All right? So Lex, we're gonna have you come out and bring the glasses of choice. And can I see those glasses before you use them? And then do we have a couple of other pairs? So, these glasses, by the way, when we look at them they are not flat. They are not flat pieces of glass. And so, we have a couple other pairs of glasses here that we borrowed from somebody's dad. If you can ... Yeah, thank you. And you're gonna see that these are much more convex than these. And sometimes, you'll have maybe glasses that look like this. Very nice. And they're causing you all kinds of problems with glare and these don't. And the reason is these are flatter than these. And so, the angle of reflection on these glasses is different than the angle of reflection on these glasses. So, just understand that. In fact, I think, John, we were gonna do a demo on one of my first Creative Lives to try to control reflection in your glasses. And we couldn't get a reflection in his glasses because of the way the glasses were. Do you remember that? They might have had a coating on them too. Yeah. And also a coating to do some things. So, we'll do our best to get you to have nice glare. All right, go ahead and put those on. Ready. Yes. So, I'd like to check out a book and ... All right. You have late fees. You have late fees, young man. All right, so we are going to turn on our modeling light here. And then, John, what I'd like you to do is we're gonna see if we can actually get a glare. So, right now we have none. So, I want you to move that up and down for me. So, it needs to come down, I believe, right now. I'll just look through here. And so, Lex, if you look straight. There you go. Perfect, perfect. Okay, let me meter that. Whoa. That is not what I wanted. There that's what I want. Okay. So, I'm gonna meter this. We have this at 10. F10, perfect. So, I'll just take a quick shot at F10. And I'll zoom this in so we can see clearly. Chin up just a hair. There you go. (camera clicks) Okay, on this shot, we will be able to clearly see that we have a nice glare in her glasses. Not from over here. Now, watch this. Yeah, not from over there but from here. So, watch this. Chin way down. Perfect. (camera clicks) And now we'll see this second shot because her head moved the angle of reflection moved and the glare went away. So, let's have you look maybe over this way. And then eyes back toward me just a bit. Perfect. (camera clicks) And we're seeing that this glare is changing based on where those glasses are. So, sometimes it's as easy as saying, "Can you just tilt your chin down?" Or something like that. But let's just say that she can't do that because of some reason. So, let's have you straight, and then chin up just a hair. Okay, so we're gonna have that glare once again. (camera clicks) And then to fix this glare, all we'll have to do is I'll ask John to raise the light just a smidgen. So, I'm gonna look through here. And Lex if you'll just keep your head right there. Yep, and then raise that up just a little bit more. Keeping going, keep going, keep going. A little bit more. Perfect. Perfect. (camera clicks) Okay. And now, what we have ... And we should have re-metered that That eliminated that because the angle changed. It also changed the shadows, it changed all kinds of stuff. So, it's sort of a trade off no matter what you're doing. You'll solve one problem and create two other problems. You'll solve those two problems, you'll create another problem. So, what I try to do when I'm trying to solve for issues like this is go for the simplest solution. So, what I would have done with this if we had a glare that was annoying, I just would have asked Lex to tilt her head a little bit to see if we could have gotten a pose that worked. Cause you saw that that didn't work. And then if we got a pleasing look, done. But if it was just something that was really annoying, maybe a big soft box that was always casting a reflection, then we would start working with raising that light. And then when we had shadows then we'd start working with adding in a reflector or maybe more diffused light. Yes? We lost the specularity in the eyeballs. Yes. So, do we add this post-production? Or do we trade off glare in the glasses and remove that post-production but have the specular highlights on that? Yeah, on this, this specular highlight is tiny. You can just barely see it there. And you can still see some of the edge of the feather. You'll also notice that this specular highlight's here on the glasses are showing up. And right there. We've got specular highlights there and on the lips. That's all changed when we move that. So, what I would do in a situation like this is let's have you lower that light again. I almost never add ... Well, I never add specular highlights in post-production. Either they're there or they're not. For me. So, we have ... A little bit lower, John. Keep going. Let's go way, way down. Keep going down. Keep going down. Go, go, go. There you go. Yep, just like that. I wanna show you one other thing that you can do to solve for this. And instead of removing the specular highlight using an angle of reflection, we can change the specular highlight by changing the source of our light. So, here we have a very, very small light source. (camera clicks) And that specular highlight is very defined and it's very hard. So, it's gonna be showing up here in the glasses again. There it is. And so, let's take that off. Yep. Take that off. Oops. Yeah, I'm trying save your face. So, what we can do is instead of having a small specular highlight like this. What if that specular highlight covered her entire glasses? What if we sort of spread it out? So, that's what we're gonna do. We're gonna throw this soft box on there. And we're gonna see what happens when we change the specularity of our light. I know, these things are crazy, aren't they? Crazy. Yeah, that'll work. So, now what we'll do, is we're gonna change the shape of that. So, if you could meter this for me. And I will ... I'm gonna do this, John. I'm gonna do this, and do front light. Raise it up just a hair. So, that ... Making the effective size of this light much larger. And we'll get it just a little bit brighter than that. There we go. Meter that for me. 6.3. 6.3. And look straight ahead. Perfect. (camera clicks) So, what we've done is we've changed the shape of the specular highlight. And I pulled this back a little bit to try to keep this hard. So, now we have a totally different highlight. It looks worse, I think. And then we'll do something even crazier. We'll move this close, close, close. So, we'll try to get this as close as possible. Nine. Okay. Nine. And I can't focus that close. Here we go. Perfect. Just like that. (camera clicks) Okay. You can see that by bringing it closer, it's changed that just a hair. Just a hair. Oh, and I didn't change my aperture to nine. But once you meter, you actually have to apply it. But you can see that these are getting a little bit softer, and if we can get that even a larger, larger soft box, then this would start filling up more of these glasses. So, you can do ... With product photography, that's what you do is you just keep getting this larger and softer. And so, eventually what would happen is that these specular highlights you'd be able to see through them. And so, it would sort of make these a little bit darker but you could see through. And you would keep these specular highlights. For me, it's changed the angle and then work with that. But you can see there's a bunch of different ways that we can work with those specular highlights. And it's something that once you start seeing them ... You know, we focus so much on the shadows and forming that, a lot of times you just forget about these specular highlights. But in a portrait like this, the specular highlights will make or break that portrait. She just solved the problem. (Lex laughs) Oh, yeah. Or she could turn the glasses off. The other thing we could do, and this is something that John does actually, let's say we wanted to emulate a window ... We're gonna pretend that this is a window. So, go ahead and put those glasses back on. And John, I'll have you move this back and forth depending on what we'd look like. So, let's say that she is now an office worker, and we wanna make it look like she has a window next to her. Okay. And then bring that down, John. Keep going down. Keep going. There you go. Perfect. And then chin up just a little bit. Cool. All right, let me do this really quickly. Nine is exactly right. This is the last shot of the day for this ... Not of the day. Of the day is the last shot of the day. (camera clicks) So, for this what we've done is if you wanted to make it look like a medical imaging magazine where the person is working next to some science equipment, and we have a light over here and we wanna make it look, intentionally, like this is coming from the window or the thing, you can actually add specular highlights to emulate a certain look. And you could also take this and put some tape over it or put some black. It's called a gobo. But you could make this look like a certain shape. And that would show up also in the specular highlights.

Class Description


The success of every photographer — artistically and professionally — is based on a strong understanding of how light works. Join photographer Mark Wallace for a three-day course that will demystify the fundamentals of lighting and give you the concrete skills you need to get a powerful image using the right lighting every time you shoot.

Mark will cover everything you need to know about hard, soft, directional, and diffused light. You’ll learn about reading natural light and manipulating it with tools like reflectors and diffusion panels. Mark will also guide you through working with light in a studio environment. You’ll explore using basic studio lights to manipulate and shape light and working with strobes and speedlights. You’ll also learn about shooting on-location and how to balance, shape, and color ambient light and light from a flash.

By the end of this course, you’ll be equipped with a whole new understanding of light that will help you to shoot more efficiently, capture consistently well-lit images, and reach new creative heights as a photographer.

Reviews

Rose-Marie Gallagher
 

This was an outstanding course! Mark presented TONS of quality information, starting at the very basic concepts and working up from there. He is interesting to listen to and very understandable. Great examples that expand the learning. Highly recommended! Thanks for bringing Mark's class to CL...I hope there will be more.