Inverse Square Law In Practice | Transcription
This is my favorite slide. Inverse Square Pye-man, kind of like Pac-man, but I am Pye. You get it? Okay, you will get it in just a second. This lovely real world demonstration, or really my real world demonstration gives you an example of Inverse Square Law in practice. This is not really good practice, but it does show you an example. We have the light placed over here on the left side. These are all different frames, and basically here we are one foot, two feet, three feet, four feet, five feet, six feet away from the light.
Let’s say that at one foot we are getting a hundred percent of the desired light that we want. When we step away to two feet, you are going to notice that I am far darker than this shot right here. This shot is virtually on the edge of being blown out. This shot is one quarter of the intensity of this shot. As we step away, you can see me getting darker, and darker.
The interesting to note is that the difference between one foot, and let’s say three feet, is extremely dramatic in brightness. That is a huge difference there, but the difference between five feet, and even seven feet is a very small difference. It’s much smaller than that initial difference. What we are essentially learning is that the further we get from the light source, the light is now falling off at a much slower pace than up close to that light source.
We have seen it in Pye’s world. Let’s see another real world demonstration featuring creepy Joseph. What have we done here? Well, Inverse Square Line, and practice, and granted he would not take a crappy photo like this in practice. This is just because I want to show you all a creepy, crappy photo, but in this shot right here, what we have done is we basically placed the flash right to the left side of Olivia’s face. Joe’s distance is roughly one foot from Olivia. Olivia’s distance is roughly one foot from the flash, and this makes Joe’s distance from the flash double of what Olivia’s is.
If you look at Olivia, she is nice bright, and properly exposed, and if you look at Joe, he is about three, four stops under exposed. Especially when you start getting to the other side of his face, he gets even darker. Now Joe happened to creep into her a little bit to close on this one, but this is where the flash is basically four feet from the model. Now what we have done here is, all we are doing is adjusting up the flash power.
Every time we take a step away, we have to adjust the flash power up to compensate, because now the distance of the flash to the subjects is much further. Look, in this one Joe was basically double the distance of Olivia, from that flash. Where as on this side, Joe is now only one foot further than Olivia. Olivia is four feet from the flash, and Joe is five feet. You will notice that the fall off is much less dramatic. Joe is actually much more similar in exposure to Olivia.
Here we move the flash eight feet away. We powered the flash up higher a little bit more, and again Joe is a creepy six inches away from Olivia’s face, and she is enjoying it. She is loving this whole thing, by the way, but here Joe is roughly nine feet from the flash, and Olivia is roughly eight feet. You can see the exposures equal out. We are having to go more flash power, but the further we get from the light source, basically the further the group is, then the more similar the relative distance is. Now Olivia is only eight feet, Joe is nine feet, and we get roughly the same light.
When we are landing a large group, let’s say the group is ten feet wide. I might need the flash maybe twenty, or thirty feet away. Depending again on the angle of that light from the group, to be able to get everybody roughly the same brightness, and there is other techniques to this too that we will cover in Lightning 201, and 301 where we take the camera, I want to take the flash off the camera. Now, before we conclude this crazy crap test, a lot has been made way to complex, the Inverse Square Law. Let me give you four simple take-aways.
Number one. The Inverse Square Law still applies to individuals. Meaning if I am shooting a lovely model, whether it be a guy, or a girl. Let’s assume it is Olivia in this instance. In this shot I have placed that light so close to Olivia’s head, that if I am shooting Olivia full length, her head is going to be so much brighter than the rest of her body, and you can actually see that.
The flash is right here, and you can even see by the time it reaches her chest, I am only getting twenty, thirty percent of the amount of light, as I was on her face. If I place a light modifier super close to somebody, it is going to still have the same effect, even if I am just shooting them individually versus as a group. Remember, if I want equal light across the entire part of the body, then that light needs to be roughly equal distance from the entire body, from head to toe.
Number two. The more people you have in a shot, well in general it means the more distance you want to have. The larger the group, simply move the light away a bit further to get even light on everybody, and that means that you are going to need to power up the light. Remember you are losing more light than you think you are. Every time you double the distance, you quarter the flash power that you have remaining. Doubling the distance means twenty five percent the power.
Number three. The basic rule of thumb. When you are trying to light a group of individuals, let’s say a group of ten people, is as each person in this ten person group, are they each roughly the same distance from my light source. My light source is fifteen feet, twenty feet away, then a difference of one, or two feet between that relative distance is not really going to make to big of a difference, but if we are talking about twenty feet from the light on one side versus ten feet from the light on the other side, yes you are going to get twenty five percent of your light on that side, and you are going to get hundred percent of your light on the other side. Just remember, is everybody roughly the same distance from the light source?
Number four is the more dramatic, the angle of the flash, the more distance that you need to have the same relative distance in everybody in the group, and here is what that means. All this means is if my flash is directly on top of my camera, which again this really depends on what tools you have with you, and what you have, but let’s just say I am using direct flash on a group of fifteen people. From standing ten feet away, then my distance to all fifteen people is roughly the same.
It might differ by six inches to a foot, or so, as that direct flash is on my camera, and it goes out to each person in the group. Very little difference, I will get roughly the same amount of brightness on every person from that angle, but as soon as I take that flash off the camera, and let’s say I don’t even need to remove the flash from the camera. I can be bouncing from a reflector, or whatever it is. As soon as I move the primary light source away from the camera, it is becoming more dramatic. We are getting more shadows.
Now that light is going to be favoring one side of the group far more dramatically than the other side. As soon as that light is at an angle, the group that is on this side is now going to be probably far closer, maybe ten feet from the flash. Where as the group on this side is going to be twenty feet from the flash. The more dramatic the angle of the flash to the group, the more distance you need. The greater the distance, you have got to pull back even further, to get an equal light from right to left.
That is why, when doing a group shot, a lot of times they will place lights on both sides. The will cross light it so that everybody has equal light, or they simply shoot group shots with an individual light in each portion of the group, and that is something we might do in Lightning 201, and Lightning 301. We will show you advanced techniques for shooting large groups with off camera flash.
At this point I know all of you have absolutely mastered the Inverse Square Law, and you understand. You can explain it to anybody who asks, and it will be like, “”Look dude, this was totally so much more simple than everybody else explains it out to be, here it is.” That is what I want you guys to do. I want you to say it with that same exact tone, and accent, and everything like that too.
CHAPTER GETTING OVER THE FEAR, HYPE, & MYTHS
- 1.1 Lighting 101 Trailer
- 1.2 Chapter 1 Intro
- 1.3 Why Just One On-Camera Flash
- 1.4 5 Reasons to Use Flash
- 1.5 4 Common Flash Myths
- 1.6 What Makes Flash Challenging
- 1.7 Chapter 1 Quiz: Getting over the Fear, Hype & Myths
CHAPTER 2: THE BASICS OF FLASH
- 2.1 Chapter 2 Intro
- 2.2 Flash-Strobe vs. Ambient-Constant Light
- 2.3 Flash vs. Ambient Light Exposure
- 2.4 Flash vs. Ambient Demo
- 2.5 Flash and Ambient Balancing For Natural Effect
- 2.6 Assignment: Balancing Flash & Ambient for Natural Effect
- 2.7 Flash and Ambient Balancing For Dramatic Effect
- 2.8 Chapter 2 Assignment 2: Balancing Flash & Ambient for Dramatic Effects
- 2.9 Flash and Ambient Balancing For Creative Effect
- 2.10 Assignment: Balancing Flash & Ambient Light for Creative Effects
- 2.11 Understanding Flash Duration
- 2.12 Chapter 2 Quix: The Basics of Flash
CHAPTER 3 UNDERSTANDING LIGHT
- 3.1 Chapter 3 Intro
- 3.2 5 Common Key Light Patterns
- 3.3 5 Common Key Light Patterns with Diffusion + Fill
- 3.4 5 Common Secondary Light Patterns
- 3.5 Balancing SEO with Workflow
- 3.6 Assignment: Flat Light Portrait
- 3.7 Assignment: Loop Lighting
- 3.8 Assignment: Butterfly Lighting
- 3.9 Assignment: Rembrandt Portrait
- 3.10 Assignment: Split Lighting
- 3.11 Light Qualities
- 3.12 The Inverse Square Law
- 3.13 Inverse Square Law in Practice
- 3.14 Corrective White Balance
- 3.15 Creative White Balance
- 3.16 Assignment: Creative White Balance
- 3.17 Chapter 3 Quiz: Understanding Light
CHAPTER 4: ON-CAMERA FLASH GEAR BASICS
- 4.1 Chapter 4 Intro
- 4.2 On Board vs. Hot Shoe Flash
- 4.3 Full Feature vs. Manual Flashes
- 4.4 TTL vs. Manual Control
- 4.5 TTL vs. Manual Recycle Times
- 4.6 Flash Power & Zoom
- 4.7 HSS vs. ND Filters
- 4.8 Assignment: HSS vs. ND
- 4.9 FCS vs. RCS
- 4.10 Chapter 4 Quiz: On-Camera Flash Gear Basics
Chapter 5: DIRECT FLASH DONE RIGHT
- 5.1 Chapter 5 Intro
- 4 Tips When You Must Use Direct Flash
- 5.3 Bare Bulbing Done Right
- 5.4. Assignment: Bare Bulb Flash Portraits
- 5.5. Grid Snooth + Direct Flash
- 5.6 Assignment: Grid/Snoot + Direct Flash Portrait
- 5.6 Assignment: Grid/Snoot + Direct Flash Portrait
- 5.7 Mini Beauty + Direct Flash
- 5.8 Ring + Direct Flash
- 5.9 Assignment: Direct Flash with Modifier
- 5.10 Understanding Modifiers
- 5.11 Understanding Modifiers
- 5.12 Direct Flash + Shutter Drags
- 5.13 Chapter 5 Assignment: Direct Flash + Shutter Drags
Chapter 6: STUDIO LIGHT? JUST BOUNCE IT!
- 6.1 Ambient vs. Direct Flash vs. Bounce Flash/a>
- 6.2 Chapter 6 Intro
- 6.3 Silver Bounce
- 6.4 Silver Bounce
- 6.5 SAssignment: Silver Bounce
- 6.6 Soft White Bounce
- 6.7 Assignment: Soft White Bounce
- 6.8 Overhead Bounce
- 6.9 Overhead Bounce + Fill
- 6.10 Assignment: Overhead Bounce
- 6.11 Event Bounce
- 6.12 Chapter 6 Quiz: Studio Light? Just Bounce it!
Chapter 7: MORE LIGHTS, REFINEMENT, & CREATIVITY
- 7.1 Chapter 7 Intro
- 7.2 Dramatic vs. Natural Light
- 7.3 Filling and Refining Existing Light
- 7.4 Multi-Point Light Setups
- 7.5 Assignment: Multi-Point Light Setups
- 7.6 Using Gels for Creative Effects vs. Corrective Effects
- 7.7 Using Gels for Creative Effects vs. Corrective Effects
- 7.8 Using Gels for Creative Effects vs. Corrective Effects
Chapter 8: CASE STUDIES
- 8.1 – Chapter 8 Intro
- 8.2 – Case Study 1 | Dramatic Sunset
- 8.3 – Case Study 2 | Desert Sunset
- 8.4 – Case Study 3 | Sinister Headshot
- 8.5 – Case Study 4 | Quick Lighting For Family Portraits
- 8.6 – Case Study 5 | Athlete Portraits
- 8.7 – Case Study 6 | Working Angles
- 8.8 – Case Study 7 | Drag + Composite
- 8.9 – Case Study 8 | Less is More
Chapter 9: BONUS CHAPTERS
- 9.1 Our Favorite Full-Feature Flashes
- 9.2 Our Favorite Manual Flashes
- 9.3 Our Favorite On-Camera Flash Modifiers
Total Course Run Time: 8H 17M 4S