The inverse square law is one of the most fundamental and important rules when it comes to lighting in photography, and understanding it can make you a better photographer. This excellent video will introduce you to the law and show you how its affects your work.
Coming to you from ZY Productions, this great video will teach you about the inverse square law and its practical consequences on your photography. The problem is that humans are inherently bad at having an intuitive grasp for nonlinear functions, and that can unconsciously lead us astray when we expect our lights to behave in a linear fashion with respect to their intensity over distance. However, this is not how light actually behaves: light intensity actually decreases as the square of distance. In other words, instead of light being half as bright when you double your distance from it, it actually a quarter as bright. And while this may all seem an overly academic way of thinking about lighting, it has very practical consequences on your work and the way light interacts with and renders your subjects, and it is well worth getting to know the law and its behavior. Check out the video above for the full rundown.
great and very easy to understand
Thanks. I thought I knew this, but you taught me some things. I'm wondering if inverse square law is only accurate for a point source of light. For instance, I assume that a laser beam has very little falloff because the light rays are pretty much parallel. So I'm wondering about floodlights and other sources of light that photographers might use that concentrate a beam.
Yes, it's only perfectly correct for a point source that emanates in all directions equally since it's essentially describing flux per unit area, but it's still an excellent guideline for most sources of light except for something like a laser.
Spot on, and that explains the different measures of light: lux, lumens, etc.
And oops...that was a pun.
It depends on how the beam gets concentrated. If you're using barn doors, a snoot or grids, it doesn't affect the results. A fresnel or parabolic reflector will. The way you can think of it is to look at the virtual focal point behind the light source where the beams would converge if they weren't redirected by a focusing device. From this virtual point you can apply the 1/d^2 - rule again. On an ideal LASER this point would be located at minus infinity.
That explains why a soft box has more pronounced falloff than a beauty dish.
At 5:27 he demonstrates a side by side to show the difference, but has surely altered the brightness of the light, thus skewing his comparison ?
You HAVE to alter the brightness of the lamp or the aperture or the shutter in order to have a correct exposure on the face. Otherwise this principle is not going to work.
In the best case - if you work with strobes - you go higher with the power on your strobe.
Sometime I wonder how you need more than 7 minutes to explain something which could have been said in just very few single and simple sentences. Moreover: the fact that light (or sound) is decreasing by the power of two with the distance is well known since the 18th century.
And watching this video is a pain: Why on earth do a lot of people wave around with their hands and arms all the times stressing every single phrase? Do they think that everything they say is that important?
You're always free to make your own video, but that requires more effort than complaining about it here on an article.
I wouldn't bother others with my limited talent and if there is nothing special to say then even more. What do you think a comment section is for? To praise only? fstoppers is more and more filled up with videos out of second sources of people who do videos not for the cause but for themselves: That is boring and annoying.
Just check it out: There are uncountable many and many much better done: https://www.youtube.com/results?search_query=inverse+square+law
You might have known this "law" since the 18th century, but I can assure you many people haven't a clue about it. Most of the photographers I've ever known wouldn't know - and many wouldn't care - anything about it.
However, using the principle allows for a subtle lighting effect on foreground and background elements, if you are using artificial lighting. It can allow for diminishing the importance of background elements in a fairly precise way, so you can get the effect you want. It can be used subtly or more dramatically.
I don't think the video showed the best example photos of that, but the information will be of use to some and it might prompt further research by those who want to know more about the practical ways of using light falloff.
7 minutes to explain this might be better than the quickest explanation - "The power of a light falls in inverse relationship to the square of the distance". I can tell you know that the vast majority of people wouldn't have a clue what that meant.
Could he have done a better job in his video? Yes, I'm sure. Does that make his video worthless? No, I'm equally sure of that.
You might consider that this video was not made for someone like you, who is already well versed in the inverse square law. You might also consider that taste is not universal - the videos you don't like may be liked, or even loved, by other people. Content doesn't have to please you to please others and one beauty of YouTube having so many variants (as your search shows) is that people can find the one that resonates with them - even if it doesn't resonate with you.
The hint to the 18th century was to point out: It has been said and told already uncountable times. I feel there are a lot of younger people (not only) who recycle the same information again and again. They are not humble, they use work already done by others to get benefits. And the audience? It gets bored if it had been listening for a while already.
That said, in just one sentence: If you double the distance to the (point, not directed) light source you get a fourth of the light to the subject.
Sounds easy and is easy. This is memorable and not some scales which show numbers nobody can calculate easily.
Reusing information that has already been discovered is something that makes us all benefit. That's why there are teachers of mathematics, history, geography and everything else. Every teacher on the planet has to teach what someone else discovered.
It might be easy for you to understand inverse square law, but don't conflate that with it being easy for others. And of course there may be better videos out there on this topic - so what? If we only ever allow a single video that is the "best" one we'd soon find there's not a lot of content on the web.
Thanks for this! and a +1 for him using a twilight princess figure
I'd have used Harry Potter figures myself! I bought some recently so I can make some videos showing the quality of the cheapish macro lens I've bought.