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Light Principles: Inverse Square Law

Lesson 4 from: Studio Lighting 101

Lindsay Adler

Light Principles: Inverse Square Law

Lesson 4 from: Studio Lighting 101

Lindsay Adler

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Lesson Info

4. Light Principles: Inverse Square Law

Dive into the three things that affect the look of the light. Consider factors like the intensity of the light, lighting ratios, and the quality of the light. Take the complexities out of the Inverse Square Law and learn how bringing the light closer or farther away makes a difference in the image.
Next Lesson: Lighting Patterns


Class Trailer

Day 1


Studio Essentials: Shutter Speed


Studio Essentials: Flash Exposure


Studio Essentials: White Balance


Light Principles: Inverse Square Law


Lighting Patterns


Shoot: Demo Lighting Patterns


Quality of Light and Modifiers


Shoot: Choosing a Modifier - Diffusion and Grid


Shoot: Choosing a Modifier - Umbrellas


Shoot: Choosing a Modifier - Softboxes


Shoot: Choosing a Modifier - Extra Stuff


10 One Light Set-ups: 1 and 2


10 One Light Set-ups: 3 to 5


10 One Light Set-ups: 6 to 10


One Light Set-ups: Pop Quiz


Day 2


FAQ for Purchasing Studio Light Part 1


FAQ for Purchasing Studio Light Part 2


FAQ for Purchasing Studio Light Part 3


10 Two Light Set-Ups: 1 and 2


10 Two Light Set-Ups: 3 to 6


10 Two Light Set-Ups: 7 to 10


5 Two Light Set-Ups: 1 & 2


5 Two Light Set-Ups: 3 to 5


5 Basic Three Light Set-Ups: 1 & 2


5 Basic Three Light Set-Ups: 3 to 5


5 Intermediate Three Light Set-Ups: 1 to 3


5 Intermediate Three Light Set-Ups: 4 & 5


10 Common Lighting Mistakes


Day 3


Solving 12 Common Problems of Studio Lighting: 1


Solving 12 Common Problems of Studio Lighting: 2 to 6


Solving 12 Common Problems of Studio Lighting: 7


Solving 12 Common Problems of Studio Lighting: 8


Solving 12 Common Problems of Studio Lighting: 9


Solving 12 Common Problems of Studio Lighting: 10 to 12


Portrait Lighting: 1, 2, and 3 Lights


Beauty Lighting: 1, 2, and 3 Lights


Lighting Groups: 1, 2, and 3 Lights


Lighting for Drama: 1, 2, and 3 Lights


Your First Studio Lighting


Lesson Info

Light Principles: Inverse Square Law

You have three main things that effect like okay first one or qualities to describe like first one is your intensity meaning like how much like how much light am I throwing out my subject is it a lot of power is it a little and we have numbers to actually describe that the next one we have his direction of light and then the last one that you have his quality and this will be a huge like this is the rest of us today so like I'm going to go into it more in depth so let's take a look at the description of them so intensity how much light there's also things called lighting ratios meaning I got one right here and one light here how are they compared to one another which one stronger which one's dimmer that's your intensity direction is it flat or directional? Is it with all these different lighting patterns is their shadows or no shadows on the last one is the late soft or is hard or is it in between or what is it so let's take a look at what this looks like kind of spreading this out I'm...

gonna move this just a little bit out of the way for the camera all right perfect so strength of light intensity how much light is there in the picture on the left over here you could say that the intensity of the light like ratios that background like I've got a light right here can you see it that light is stronger than the main light. So intensity wise it's brighter ok and then you could say maybe this is dim like that's like the amount of it intensity would also be like is it has to pointing is f eleven because that's saying how much light there is generally if you're saying like the light is f sixteen, that means that in order to get your exposure correct, you had to close down that hole really, really small so that not much water could get in, which means you were throwing a ton of water at it. So if you hear someone say ok, the light is that sixteen it's a pretty bright light that's a lot of what is a lot of light you're throwing at it if they say however, the light is two point eight, then it was pretty damn and you had to open up really big in your aperture to let enough light and to get the correct exposure so those air like intensity descriptions are the next one you have his direction of flight, so the picture on the left it's pretty flat, not much directionality there aren't many shadows where is the picture? On the right? There is shadow, there is direction of light, there is drama okay, and we'll go into all the different tools you have for all of this, but I want you to understand where I was going. And then lastly, the quality of light and the two easiest descriptions are hard lightens off, like, of course, there's everything in between from those two extremes, but how you can judge this is if you're judging by the shadow created by her nose, I put the light in the same position in both of these photos, so if you look at the picture on the left, you don't really see the edge of the shadow by her nose it's like right here to the little bit of shadow because it is soft light so the shadows air soft, which means that they have really subtle grady in't there not clearly defined, the light is softer that has left contrast where as picture over here on the right, that is a very, very crisp, harsh hard shadow. So when someone talks about soft light it's usually talking about that blending between shadow and highlight, is it really slow and gentle and subtle? Or is it really abrupt and crisp? Hardly is abrupt in chris soft is slow and subtle, so these are the things when anyone's describing light to you, they'll be talking about the intensity of it direction of it in the quality of it and that's pretty much all they talk about over and over and over again and so that's where we're going with this as well. All right, so we're going to talk about intensity did you know that you can make a white background white, gray and black without changing anything but distances? I did not know this forever, okay? And I didn't quite get it, so we're going to see how this plays out. So the first thing we're starting with his intensity of light and this thing that I used to get super freaked out about called inverse square law, ok, but well, I was going to say it, so when you hear, you know oh, that's what they were talking about, people make it way more complicated than it needs to be, so we're going to keep it nice and simple and talk about in practice practicality what does this whole thing mean? So a weight background like we have here, I can make it white, I can make it great and I can make it black depending on where I place light and the subject. I said, this is what it means to you, all right? So in practice in practicality letter a if you move the light closer we're further from the subject it varies its strength ok, so let's just take a look at that in practice and I describe this just like the bucket of water because if I stand way back here and I throw a bucket of water less water reaches her, it spreads out and it doesn't hit her but if I stand really super close and doused her with a bucket of water, a lot more of it will hit her lite is exactly the same as that so for example let's get a on and I'll take that from you that oh, by the way, if you have one of these, don't have your subjects put their fingers on it they're actually pigments and you're the oils in your fingers shift the pigments which then make them useless because then they're not the right color anymore so which was hold decides gently oh she's good she's good she's a pro she already knows okay so let's take a look and like I said, if I wanted to not guess for example you do the light meter and I know where to put the camera to start off with a focus on perfect. Okay all right so I am not going to change anything except for where the lightest my camera is going to say the same power is going to say the same on the shrewd like nothing at all is going to change but I'm going to back this up not too far. All right, let's, take a look at the difference. So can I see those two before and after? Okay, so nothing changed. But where I put my light as I moved it back, the water wasn't reaching as far, so it got darker. There are certain mathematical equations on trying to figure this stuff all out. I wouldn't bother unless you're shooting film. If you're shooting film, go ahead and learn this at this point. You don't really need to know that. Just know that light falls off exponentially. It's not like if I double the distance, then it's just like half the power. Because you would think, right if I have a certain amount of a bucket of water here that I back up twice the distance you think it has them out reaches its not it's. Much more than that, it's. Actually, a quarter of the amount that reaches so just know it's. Not like a straight line. It gets less and less and less more drastically. And so, by the time I get to the edge of this this stage here there's like no water reaching her at all. So it's a very drastic drop off, so that would be a letter a the closer I bring out the brighter it gets further I bring it away the darker it gets distance makes a difference so let's say you're shooting in the studio space where it's like really small it's really really really type it might be a problem if that light is really really close and you can't turn it down any more but let's say you're in this space and oh man I turned my light down all the way and shooting at a small aperture but I don't want to shoot a f twenty two I how do I make this dimmer you come back your light up like distance actually will make a difference there are down sides of this which will get to it it's coming okay so kind of the keynote back up all right talk about this so um next one is bring the light closer or further away two very fall off and background ok so we're going to take a look at what this actually means can I have you just a dumb shit? Can you back up like two feet all right so if I put the light very close to her the background will look one way if I correctly exposed for her when I backed that light far back and correctly exposed her the background is going to look totally different all right? So here's why when I bring this light really really close it got brighter which means I have to shoot a smaller aperture so maybe I'm shooting at s eleven so I darkened things down so that it was correct for her most of that bucket of water is hitting her it is not reaching the background so that background will be darker so it is a rule some basically how to think of it is if you're trying to get your background darker, bring that like closer to your subject and then move your subject further from the background because then the water can't reach and it's mostly hitting her so for example take a look and again if you want to not have to guess like I would guess you can actually figure out what africans should aperture to shoot at let's see? So take a look at the background here, okay? And I mean it's just just a little bit. Okay. All right, so one of the things if you take a look it's some it's not white notice that the backer that we see here is actually white to our eye but the light falls off it gets darker. Okay, if I want this to be even more drastic ready can you help me with your chair? I'm going to move us way way, way, way, way back way back like this way perfect way they're perfect, okay that's great so the same thing I've lived her back far away from that background and I want to move this light nice and close so she's going to be bright no lights hitting that background or minimal light so it's going to be much darker so let's see before and after it's going to get a little darker you know that late background got darker okay I'm gonna do one even slightly slightly more advanced thing just a little bit which I see if I get this in we're going to talk about this in the modifier section but this is something called a grid and so if I have the script okay I might need your hand on wasting what a great does that focuses the light and it prevents fall off I think that's in solidly okay, perfect okay, we're going we're going to attempt this here okay? So grids there are grids for softball has there are grids for silver dishes their grids for beauty dishes were well take a look at how these work but right now what it did is it focused all the light in so that bucket of water cannot reach the background hardly at all so we start off with something that was pretty light and then a little bit darker and now if you take a shot at her and see but adding that grid the background is completely black because I made it so that the light couldn't spill onto the background so this tool has less to do with inverse square law but I wanted you to see how I made that background black but what I did want you to know is if I bring the light or if I bring her closer to background the backgrounds going to be lighter so I got to pull her away and if I want the background to be darker compared to her I gotta bring that light closer so let's, take another example of what this looks like in reality so we just saw all of this we saw the changes that it made ok, how about the other extreme things that are closer together are more similarly link so I'm gonna have you go back back this like little more made three more feet yeah, right there. Okay, so for example, you saw what happened here. Everything got dark, okay, so inverse square law it has that whole fancy thing things that are closer together and more similarly distanced from the light will be lit more similarly. All right, so here's what it means if I have no one to take this off and in this makes sense if I'm another person posing with her and I back up, I will be darker right? Because I'm further away from the light but the closer I get to her more similarly let I will be ok so another example of that is relative distance taking a look at this space right here if I take my example again and I bring this super duper close the relative distance to the light is more dramatic which means that light is pretty darn close to her compared to me it's two or three or three times distance so I'm going to be a lot darker but when I moved this all the way back the relative distance it's not really that much farther from me that is her since it's backed up so far like yeah it's a little bit farther if you actually go by numbers but relatively now that it's far away I'm not really that much further back, which means by back in that light up we're actually going to be a similar exposure as soon as we bring it way up close to her I'm going to be a lot darker so like the's relative distance is all make a difference so in the example of the background if I bring it super super close, that background is relatively far away from the light compared to her so it'll be darker if I bring that light all the way back it's a lot closer and it will be later so we'll just take two quick shots of this one okay perfect lovely ok, so in this example nice and close to her for good model don ok and so her shadow is on him a little bit but you'll get the idea like the light on his face it's much, much summer however if I back this way up maybe back up a little more like we'll say here there's a couple things we got to think about well, first of all it got dimmer so I'm gonna have to adjust but distance wise let's try about their strike this they'll be a lot more similarly lead no, I'm writing up a little bit okay, so if you can put those two side by side in the dark one two steps ago so if you look there's some like you know it's not the same light but look how much darker for use in this one. So what you want to keep in mind is these kind of things when you bring the light closer to your subject it is relatively a lot closer to your light so the background gets a lot darker. What if you move that light back? The relative distance is not as dramatic and so the background will be later. So notice even just with that distance the background here's pretty gray in the background here is pretty white and you can take this to extremes so let me show you how that works practically with a couple things on kino all right? So how it plays in your real world portrait moved like closer or further to very strength if you need to next one bring the light closer further away to change the background closer it is to her the darker the background will get further away it is there more similarly distance it'll get lighter and then the last one is to bring subjects closer together their distance will make them more similarly with so this is what you like really care about so how it would come into action would be talked about the first one changes in the light change exposure so let's say my light was just a little bit too dark I can bump it in a flight you know I could make it brighter you could do that for practical purposes the other one in reality we talked about the background changing this is the background one to make the background darker put the light closer with the other one is to more evenly late groups you need to pull the light further back. So let's say that john in that example was a third rollback in a group I was shooting like a shooting like fifteen, twenty people he's in the third row back when my light is that close the relative distance he's going to be dark so when you light a group you've gotta pull your leg back and make sure it's approximately the same distance from everyone and that doesn't just apply to front to back that side decide to because if you think about it, if I've got someone over here five steps have you signed up for a quickie one it's just easier than like waving ok like right there, even if I'm shooting this way, she is like four times further away and cause the lights exponential, it's she's going to be significantly darker, even if she's not I mean she's only like a foot behind has nothing to do that it's that distance from the light so far light in a group I've got a center it more and pull it back you know their relative distances are a lot more similar, so this is where like really comes into play and then the same thing if you're in your studio and you're trying to get a background darker mover waste in the background move the light and so this is the realities of why you care thank you I think that's a good stopping point. Alright, fantastic. Well, thank you so much to our model. Yeah, and we'll be seeing you throughout the day as well. Right? All right, fantastic. And when I come over here and going you all right, so, uh, first of all, people just absolutely love your teaching style so thank you for breaking it all down, but let's take a few minutes to ask a few questions so let me know raise your hand in here if you was have any questions for starters and if not, we have plenty coming through from books, so I'll start there ok? So we're talking here about studios and we're talking about using strobes and such so people are running first of all, we're going back to the basics are you shooting and raw or j peg? I'm shooting in raw, especially if you are going the guessing no light meter route just so I have a lot of flexibility in case my exposure wasn't quite where I wanted it to be great. And so some people have been talking about how in other classes they have heard that if you're shooting and raw, can't you just set it on auto white balance? Because then once they're in post processing, you can just easily change it what's the difference if you're say shooting a landscape versus having control here in the studio? Sure okay, so you can see audio, but the problem is things change, you're live in landscapes I mean it does actually changing landscape to with the light and what not, but in this instance your modifier your distance, what your subjects wearing that are all affected, how a bottle appears so you want to pick a baseline raw you can change anything but then you might have to change it every photo if you least keep it consistent then get that great card then it's just one easy change instead of hundreds perfect thank you yeah ok so this is a big one I love that people are voting on questions this one has twenty eight votes oh okay all right dylan just to set the stage for people because this is a one o one class this's from whiskey bravo charlie what benefits do strobe lights have over continuous in studio settings okay on what does that even mean maybe for people perfect right so this is something that I'll get in tomorrow when you're figuring out what lights to buy do you want continuous life which means they don't flash it's just putting out light and usually those air leaves constant fluorescent lights and there are things called hot lights which are tungsten and we'll talk about that tomorrow yeah tomorrow exactly whereas the strobe is that quick flash of light in general it is cheaper to get more output by going with strokes so what happens is if you are going with a constantly like a fluorescent light and you're trying to light a group sometimes of leading a group you need to be at what like faa if it's a deep group it's hard to get that much like out of a constant like and so to really get that you end up going into a gym eyes which are like thousands and thousands of dollars are really, really strong led panels and so you get a lot more output from going with strobes and then it's also easier I think to control the variability like control the main light related to the background light you can do that with constant lights you just have to buy the really expensive one so this is just easier great thank you and then when you're talking about okay we're using the strobe so what what do you call the light that is coming off of right now the way I see it flash go off but what is what is that? That is an awesome question okay, so this light right now is called the modeling like the late that's on it's not doing anything to our exposure whatsoever all it's helping me dio is see how the light looks on the face roughly and when you're setting the modeling like there's two different settings you can be on one of the setting is called surgical proportional, which means it'll actually like let's say that maestro but at half power it'll put the modeling light at half power so it's trying to give me an idea of ratios like if I have multiple lights in the scene I can see kind of how they're relatively bright compared to one another or what I have in this instance is just full power it's not reflecting what the lights actually going to look like whatsoever as faras output it's just I want to see what the light looks on the face from putting it in the right direction if the shadows are looking right give me an idea of where to place it so modeling lights I use them all the time because otherwise you don't you're shooting blind you don't know how where your lights are going, how you're using it great and I'll hand you know what the size of the speedy dishes this one is twenty inch white great folks were asking about that as well okay, so the other biggest question that people were asking about this morning is does all of this apply if I'm using speed lights and are we going to talk about speed lights in this class? Okay, so we're not going to talk about speed lights did a location lighting one o one class which had a full day on speed lights as well as a full day of studio lighting on location. All of it applies so far like we'll get to a point where some of the things don't apply but shutter speed affects the same thing if you're shooting with your speed lights and manual not tt l it's a different thing the modifiers and how you choose which modifiers right for the job that's the same with speed life the inverse square law that distance in relative distance of light that's the same with speed light so latest light it's just you choose a different light for a different job rex stipulating eso let's talk a little bit about I have let's just do really quickly rapid fire folks have so many questions coming in and a lot of these questions we're going to cover ok so just give me a yes or no okay all right so for those breaking into studio lighting is that better to start with flash and soft boxes or jump right into strobes and continuous lighting if so when should be beginners what choose what brands more or less tomorrow morning great okay I'm starting with speed lights are they enough? It depends on what you're shooting and kind of tomorrow wait I think this is a rapid fire doing radio triggers affect your sweet light I'm sorry do radio trevor's turner's affect your sink speed they can if you buy expensive ones but this is one of one so I'm not getting into it okay but and yes a lot about this are we going to talk about strobe versus continuous yes yes ok one more if you had to choose between octo box and a large rectangle soft box which would you prefer I'll talk about that later today segment I get two or three so yes yes

Class Materials

bonus material with purchase

Keynote 1
Keynote 2
Keynote 3
Gear Guide

Ratings and Reviews


If you're on the fence about this class I can easily answer your concerns. BUY IT. Lindsay provides top notch professional education while keeping things interesting. Her words are precise and direct. I actually felt GOOD just watching and learning. I mean, like someone surprised me with a cupcake kinda GOOD. After the class I could immediately see improvements in my photography. The best part is that I learned enough to see the wrong in my setups. Knowing what's wrong is just as important as knowing what's right. She is funny, easy going, energetic and filled with knowledge. I would also highly recommend her Posing 101 class as a must have addition to this course. I feel like I have learned more than I could possibly use. I will be going through this course over and over again just to make sure it all sinks in. There's THAT MUCH she offers that you will always learn more with each time you watch. I hope this helps someone make the decision to up their game. That is exactly what it did for me.

Jason Ashley

I loved this course! Lindsay spent so much time with explaining each set-up in-depth that anyone picking up a camera could understand how to accomplish their lighting goals. This course covered so many unique (but, most likely to come across scenarios) and how one would approach the challenge and how to successfully accomplish with incredible results, not average-sub-standard or basic results, but above entry-level standards, high-level, money-generating lighting expertise! ZERO laziness in her explanations to the point where she is constantly refining her course in the middle of the 3 days. Her passion gleams throughout each days lessons with so much energy. You know she really wants her students both in-person and through the screen to be successful in whatever type of lighting they choose to dabble in. I am so happy, I have bookmarked, and i'm so happy and fortunate to have this course to reference for hopefully –everrrr. Thanks!

Beatrice Palma

Hi, I am Beatrice from Italy. I think this class is superb. I finally understood what are the guide lines to follow, I tried for years but never found such a good explanation. Lindsay is a wonderful teacher, she explains in a simple way, she shares a lot of knowledge and she shows in practice what are the results of every single choice. Thank you so much, it was really amazing and super interesting!!!!

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