Understanding the Inverse Square Law in Photography
ฝัง
- เผยแพร่เมื่อ 4 ส.ค. 2024
- In this video I explain the Inverse Square Law, why it's important to photography and how to use it to your advantage when shooting with flash.
🔔 Subscribe for more free photography tutorials: th-cam.com/users/selfhelpphot...
✅ Recommended playlists:
Learn How Your Camera Meter Works And How To Use It:
• How the Camera Meter W...
Learn All About ISO, Aperture & Shutter Speed:
• How Your Camera Talks ...
How To Get Started Shooting With Flash:
• Complete Off Camera Fl...
❤️ If you find my content helpful, become a patron: / heniadis
Disclosure: Some of the links I use are affiliate links, meaning, at no additional cost to you, I will earn a commission if you click through and make a purchase.
Want to save time and learn a LOT more? Check out my video courses:
The Guide to Shooting in Manual Mode: shp.photo/manual
Understanding Flash Photography: shp.photo/flash
Mastering Lightroom: shp.photo/lightroom
Find me on the socials:
Facebook: / selfhelpphotographer
Instagram: / heniadis
Portfolio: www.spyrosheniadis.com - แนวปฏิบัติและการใช้ชีวิต
![CAMPปลิ้น | EP.79[1/2] แก๊งไทบ้านพาบุกเมืองบั้งไฟโก้ ยโสธรรรร!!!](http://i.ytimg.com/vi/Ldr3_fvTEXk/mqdefault.jpg)
One of the best video's on that subject out there! Thanks!
Good stuff bro... I love that you open for correction! That means a lot!
Need to define the term stops and how it is worked out for a complete understanding/inverse squad law was on point.
This was the fastest 15mins I've seen. And well explained. Thanks
nice! i love this video :) i'm nearly subscribed every photoraphy chanel on youtube but i've never heared of this formular. Good to know.
Thank you Spyros.. your explanation are very helpful!
Watch this video. I almost passed on it, thinking that 15 minutes was too long to explain this, but that's absolutely not true. The math part, and the overall concept, comes easily to me, and it may to you, also.That's why I thought there wasn't much more to explain. But how to apply that in a shoot is what the video is about. Useful stuff.
Great video! helps me a lot.
This is ver helpfull mannn..
this is what i wanted it
i didn't know how much light source power to cover another face from calculating distance
so now i know it
Thanks
You are AWESOME!!!!!!!!!!!! Nuff said.
Nice and very helpfull Tutorial
What can I say .... SPOT ON ! That just about covers it all very clearly. Thanks.
Very interesting examples.
Brilliant!
Dear Spyros, Thank your for sharing the Inverse Square Law. How do you apply for macro photography. I'm using 2 flashs with macro lense. I'm setting my camera at F36 or 40 to maintain full depth of field. Some photos of flowers outdoor with black background. In some case it look good but some not so natural look. I appreciate your advise. (Note , I used 1/2 power on one flash and the other 1/8 power to avoid 'flat picture'.
I like this channel.
Thanks.
Spyros ... if the strength of light source could not be increased, could the same effect be realized by further opening the aperture, adjusting the shutter speed and ISO?
BTW, thank you for a very, very helpful video.
Thank you, Spyros. Again, terrific videos ... great production value, extremely informative (yet fast paced) and your passion is contagious.
A treasure trove of both praxis and theory.
One mistake: The snoot will not change the rate of the fall-off. It's still the square of the distance.
(Of course if one shot is with a snoot and another shot is without it, things are different because you've changed the light source.)
starting to make sense - somewhat... I'll just keep rewinding until it becomes obviously clear. Seems like this ISL is more of a "foundation" guideline than anything else. Simply understanding that moving the subject further (or closer) to the light source creates or decreases shadows.
Yes, that's a good way to understand it. The preciseness of it can be useful, but really just understanding the general principal goes a long way towards making it useful in real life shooting situations.
Surely the light modifiers can't buck the laws of physics. I can see how they might shape the beam, or concentrate it but if we have a base measurement at full power at any distance then at twice the distance the power must be 1/4 and so forth or am I missing something here?
I would have thought that the inverse square law does apply to light modifiers, but the law is relative so if a snoot is effective in concentrating the light beams such that they travel "more parallel" then they will diverge more slowly and the amount of light striking a given surface area at 1 foot from a snoot will be greater (and therefore appear brighter) than without a snoot. If this wasn't true then using a snoot would have no more effect than moving your flash closer to the subject by the length of the snoot. Accordingly, a snoot at 2 feet will be 1/4 of the brightness it was at 1 foot, but this will still be brighter than an equivalent but unmodified light source at 2 feet (i.e. the snoot light is 1/4 of a higher starting value).
The inverse square law is about the divergence of light. The individual photons of light are not losing power, they are just spreading out so there are less of them reflecting off any given surface area which they strike and therefore the surface doesn't appear as bright.
Note, you can't shape a beam of light , it will always travel in a straight line unless you have the gravitational pull of a star, or maybe a large planet.
I'm no physicist, so take the above with a pinch of salt.
Rob Yallop Your aassumptions are correct, changing the size of the source does not affect the laws of physics, the power will still reduce according to the equation, but what WILL alter is the hardness or softness of the light. A snoot will seem very bright because it's size relative to the subject is small in comparison to a large softbox this affects the hardness or softness of the light, it's quality not it's quantity.
+Rob Yallop The Inverse Square Law actually describes light that is emitted from a 'Point Light Source', but for all intents and purposes it behaves in exactly the same way if you place a modifer between the light and the subject.
Obviously the light will be disipated and lose power when a modifier is used, but for the accuracy needed in photography (or rather lack of it), the inverse square law is still a very useful method to calculating changes in exposure.
What can I say great video and explanation . . . but . . . my head hurts.
Jump 1:55 to skip the sales pitch...
make more simple please, mucho habla.
The basic idea of the inverse square law is this:
As light travels over distance, it loses intensity at a predictable rate.
That’s really all there is to it.
Now, if you want to use that predictability to figure out the intensity of a light source (such as a flash) at any distance from the light, you have to do some math.
To do the math, you need a unit of measurement. It doesn't matter what unit of measurement you use, but for this example I will use the standard foot.
To figure out the intensity of the light at a distance, simply square that distance.
The intensity of the light at that distance is equal to 1 / the squared distance.
For example. Let's say you have a flash set up and your subject is 2 feet from the flash.
First we square the distance (2 feet)
2*2 = 4
Then we invert the results to determine the intensity. (4 inverted is 1/4)
So the intensity of the light at 2 feet from the light is 1/4 of the lights intensity.
IMPORTANT NOTE:
The intensity you calculate using the inverse square law is relative to the initial intensity/power level of the source.
So if your flash is set to full power (1/1), then at 2 feet the intensity of the light is equal to 1/4 of the flash at full power (1/1)
If you had your flash set to 1/2 power, then at 2 feet, the intensity of the light is equal to 1/4 of the flash at 1/2 power.
you always talk about foot, how about the metric system?
+gytn25 Your Speedlight Manual publishes metric with the Guide Numbers…Better yet? Are you telling everybody on TH-cam that you cannot convert 3.28-Ft into 1-meter…10-Meter is equal to 32.8-Feet? Seriously?!
Metric Converter iPhone Apps? Hello?!
So how about seven meters, is like 22.96 feet, which equals 275.590551 inches. Well, that's just fucked up man. I mean 1 foot is like 25.4 inch, which is 914.4 yards...... just use the metric system, makes things so much easier... anyways, have fun with your calculator! ;)
+gytn25 1-Foot is equal to 12 inches; 3 Ft=1Yard (One Step; One Pace;American Football Referees use Pace to walk penalty yardages); 22.96 feet = 7.6533 Yards = 22.96 inches…Use Pace Count to step off your Flash-To-Subject Distance measurements...1 Yard = 36.00 inches…
Like Spyros has mentioned, stick with Metric System or the Imperial System (American Measurement)…The Tables in the NIKON Manuals are configured with both Metric (M) and Imperial (Ft.)...
slow down, between your hands moving excessively which is a distraction..... your simply talking to fast........ too much caffeine!