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5 Behaviors of Light: Inverse Square Law of Light

Lesson 8 from: Picture Perfect Lighting

Roberto Valenzuela

5 Behaviors of Light: Inverse Square Law of Light

Lesson 8 from: Picture Perfect Lighting

Roberto Valenzuela

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Lesson Info

8. 5 Behaviors of Light: Inverse Square Law of Light


Class Trailer



Intro and Who This Class is For


3 Groups for All Lighting Scenarios


My Progress in Lighting


Analyzing Circumstantial Lighting


Circumstantial Lighting Q & A


Using a Reflector the Right Way


5 Behaviors of Light: Overview and Angle


5 Behaviors of Light: Inverse Square Law of Light


5 Behaviors of Light: Relative Size


5 Behaviors of Light: Relative Size Continued


5 Behaviors of Light: Color


5 Behaviors of Light: Reflective Surfaces


5 Behaviors of Light: Q & A


Location SWOT Analysis and 10 Things to Look For


Location SWOT Analysis: Examples and Exercises


Overview Q & A




Speedlites: The Basics and TTL


Speedlites: Manual Flash


Speedlites: Zoom Flash


Speedlites: Zoom and Rotating Flash Head and Reflectors


Speedlites: First Curtain vs. Second Curtain Sync


Speedlites: High Speed Sync


Speedlites: Optical vs. Radio Systems


Speedlites: Groups and Channels


Location Lighting Upgrade Examples


Indoor Lighting: Building on Ambient Light


Outdoor Lighting : Speedlights in Direct Sunlight


Outdoor Lighting: Using Speedlites in Shade


Outdoor Lighting: Romantic Look and Patterns with Speedlites


Indoor Lighting: Creating a Window with Strobes and a Curtain


Indoor Lighting: Moody Light with Speedlites and Gels


Indoor Lighting: Reflective Surfaces


Indoor Lighting: Shooting Against a Window


Indoor Lighting: Adding a Reference Point and Ambience


Indoor Lighting: Shooting into a Mirror and Creating Separation




Why You Need to Learn to Get it Right In Camera


Location Photo Review and Analysis


Intro to Reception Lighting SWOT Analysis


Reception Lighting Setup


Image Critique: Lighting Problems and Solutions


Don't Limit Yourself As A Photographer


Lesson Info

5 Behaviors of Light: Inverse Square Law of Light

Oh, inverse square love life. Everybody like, uh, members blye square love life get back to normal. Um, I've seen people discuss this in the most complicated way imaginable and it's all good, but I never understood because of that, it was like, what the heck are you talking about? On more importantly, when I understood the principles, I never understood how to apply them like that was just me being not that smart. You know, I think he's left, so to make this super super super simple. First before we do this, I drew some little diagrams for you so you can see the importance of the inverse square law of light. I did it the best way I could to show you visually what's happening. Okay, so we have amanda w here. Why do I say you're in the show like it's, so frustrating, right? If I put this light really close to her face, the inverse square law of light simply states that the closer you are to the light source or your eyes are really hurting. Basically, the stronger the lights going to be o...

n as soon as the light source gets farther away from the subject simply that the inverse core love light says you're increasing the intensity of light on the subject by how much that's the formula but the formula states that by a lot that's the mathematical way. Okay, so if you want to keep things simple, easy to understand. Just remember this the closer your subject is to the light source. They're more intensity of light is going to be on the fall off. Off light is going to be totally fast. You see how that side of her face is totally black? Okay, and then you ask him yourself. Why? Why does that happen? Happens because the rays of light are all illuminating her no light can escape. So look, if I put this here, light radiates, it goes into many different directions. Right? So if I put this light here do you see how much a lot of the light is radiating over her head and towards the floor and tours everything. Look, here is the light. Make a cone make a cone off light that light's kind of going like this, writes and some race go past her head and some rays are illuminating her body on some race are going and illuminating my good friend. Um but when you do this, how many rays of light can escape? None. So that means that this part of the face is receiving no race off light this part of the face is receiving all the race off light no light can escape so it makes as soon as the light stops illuminating the shape of her face is going to go black that nose are you hurting me? Is it hard totally I'll do it to myself just to suffer it's really hard okay um now is that they could look at the little illustration on the screen if you look at the screen it says he shows here all the race are illuminating his face because we have no cece and chains and I'll eye sockets that becomes like the block off light so if a man has a nose right I can see it if you illuminate amanda's knows from this direction their nose blocks the light from the other side of the nose door on if no race of light are escaping towards kenna bouncing against that war and reflecting back to illuminate the others out of her face it's going to go black because it's receiving no light so take a look at this this is receiving the entire like how dark do you think the environment will be here? How lark it's like it's a real question how dark do you think she will be illuminated? Well because you can change your exposure to match the lighting on her face but how dark is going to be the background talk because there's no light spilling into the background because the whole light is right in her face cool. So the room is going to be dark why's that important? Because what if you have an ugly background? What if you have an awful mirror or a plant? That's terrible hasn't been watered in a long time. What have you shooting in an environment? That's. Just not attractive. Use the inverse square law of light to bring your subject closer to the light. If you live in germany or in cr oh, use but lights like this put the light closer to her illuminate exposed for the bright light and the rest goes black. Removing, distracting elements is fantastic. What a beautiful thing! You don't even have to move any furniture. Just dump it with blackness, okay? This is what you get. A crazy amount of light on one side but black background all the way through. Cool. Okay, let's, try let's. Try this example I am now I have now moved away from here to here. Do you see race of light escaping her face now? Very simple. Right? Uh, let me try something here. This may or may not hurt. Okay, okay. Do you see how all the race hit her in the face? How? How many of these rays went to this side, nothing now let's, try this. If you look at the wall behind you you see what his creative life right there you can see that the light actually reaching creative life look at that you see it that's it because of that the light rays come out of the flash they expand like this as they come out some of them here her aa lot of the race don't they go towards the wall? They bounce around and then they come and hit her in the face again cool um you get this picture do you see how the background gets brighter? The backing is brighter here because more light it's reaching the background check take a look at the first picture you see how that's pitch dark now this one has more light now let's go to the next one now I'll stand here on I'll point my flash w do you see how very few rays of light to hit her? But the rest are kind of illuminating the whole scene, so if you lightest far away that lighting on her it's going to be more even because the light some race are hitting her some rays air hitting the walls, some razor hitting the roof they're all kind of having a party on in they're all illuminating amanda all the way through evenly that's why the falloff becomes a lot less and less and less at first the fall of is very strong because all the rays illuminate this side nothing you know a humanist outside as the race off light radiate you can see how the other side of her face starts to get even do you see that look at that until basically there's no difference let me try that again look out when I get closer look how this starts to get darker and darker and darker and darker and darker and darker and darker cool so you don't have to do all the math and complicate your life just know that if no rays of light are escaping nothing's gonna bounce off other walls that side of the face is going to go dark cool okay this is what you get a look at what you could write that background this this is another one do you see how that background is distracting the awful plant I mean I would never buy that plant um on that table has a thing in the middle bad news um that's that's how far do you think that light this basin? The inverse square little of light give me a ballpark far because you can see the exposure's pretty even right now watch this now how close the light is the light it's right on the face so how does this apply to you as a photographer? Well kind of a lot because a man that can just stand here uh let's go closer to the window now phase the window okay hold I'm not that much like this this then right there that's good click closer to the window so he could get more light in your face come this way where there's like this for a second think this here stand here ok go ahead be careful let me help you now face this way and don't fall please if you fall I'll take a picture if you're photographing the way we normally photograph which is close to the window which is wishing that what we always do you photograph somewhere this way if it's a girl you're splitting her face you're getting split like that's awful like that's why it affects you and then if you put her mom or her aunt or something and you uh take it could you come in for a second if you put her here stand right there's good send right there. Um uh what's ahead. Can I get two more people over here, please? Two more maybe just go back down for this example get close together they're close together. Okay, great. You're the photographer you're taking pictures like this right? Boom boom boom who's getting the best light the light source is here she's getting the highest amount of light on in the inverse square law says that you're losing what is the technical term I used aton of light every inch you move on until it starts to taper down right based on the formula right it starts to taper them so if you're not a mathematical person remember this if you have your subsidy if your subjects are close to the window the light fall it will be very fast on the people far away will be dark if you are far away from the window that lighting is pretty is going even out cool so if you're photographing bridesmaids or a group of people for a fashion shoot or whatever you're doing this is pretty much the worst possible situation because you're making all the light on amanda and you're putting nothing on chris santa on her okay, now if you're if you're watching on the internet you're saying roberto I don't get it because she looks just as bright as she does that's because we have a bunch of lights he looked back illuminating backlight that her okay, thank you guys thanks if you are the mathematical kind this is for you if you are like me or the rest of the people you can probably nor this but uh wow those numbers they're not appear the way I said okay, I'll just say real quick at the starting point of one foot away from the light um you're receiving one hundred percent of the lights because all the rates are hitting your face as soon as you go to two, feet, the life starts to spread on. You receive on ly a court, only a quarter of what you used to receive. So three quarters of the light goes away on. Then it goes like that well until they start to taper off. So you go from one hundred per cent of the light when you're really close to it, too. Seventy five, so only twenty five per cent of the light toe on ly eleven to four to four to three to two to two to one to one. So the farther you are from the light source, the more even it becomes the closer you right to the light, or is there more drastic? The fall of will be okay.

Class Materials

Bonus Materials with Purchase

10 Elements to Look For at a Location

Ratings and Reviews


Im sitting in my office listening to Roberto with my earplugs on and I know I have already left 2 reviews but he's so funny…. my family comes into the office asking me "whats so funny" Roberto makes me laugh out loud with his jokes but at the same time, he is SO great at teaching. Im watching for second time to make sure all his good info is ingrained. HIGHLY recommend you take his workshop on Picture Perfect Lighting if you truly want to take your photography to the next level! WOW thats 3 reviews now…can you tell I am impressed

Maureen T.

I'm taking a portrait photography course at NYIP online. one of the mentors there recommended the posing book by Roberto. I ended up ordering at the library the posing and the perfect practice book. I fell in love with both books...ended up buying them and signing up here for the year membership just so I can take all of his photos courses. I spent most of my weekend doing perfect lighting course here I am in love with the way that he teaches! He makes something so difficult and challenging for me make sense. I also like that he challenges us photographers to be true professionals. I am thrilled to have discovered Roberto and already noticed my photography is better in the short time that I've been studying him.


Roberto has the personaliyy and gift to relate to others.He is honest and shared some of rhe disaters that occurred, even with high paying and important clients when he failed to follow his proven and tested approaches. He has shared from his extensive knowledge developed by hard work and effort to master his craft. His dedication in attacking his weaknesses and making them a strength is inspiring. I have purchased many CL classes and all have worth the investment so I hesitated to purchase this course because I didn't think there was much new information. However the clear teaching and extensive knowledge shared by Roberto in his unique style caused me to purchase it gladly and believe it is an exceptional value. Roberto has shared his extensive tools, but you will never be the master of the craft without putting in the hard work and testing that roberto testified to. Thanks again CL for bringing the best to us and Thank you Roberto for taking the time and preparation to achive excellance in in this class.

Student Work