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Light Falloff Cheat Sheet Card
As part of my ongoing exploration of portrait photography in general and flash studio photography in particular, I wanted to examine the effect that a large light source will have on light fall off. This was a great chance for me to produce a new cheat sheet to companion the portrait lighting cheat sheet and reflector cheat sheet that are already out there. (And this time we have a special guest, read on...)
What is Light Falloff ?
When ever we use a light source to illuminate an object, that object is being hit with multiple "rays" of light. Some of those rays are hitting the object in the place which is nearest to the light source, and some of the rays are hitting the subject where is furthest from the light source. OK, nothing new until now.
As a crude generalization one can argue that the light that falls on the closer side to the light source will be brighter then the light hitting the furthest side. This is because the light will scatter more when it makes it long journey to the far side. (This is not true for focused beams and laser, but this thumb rule can be applied to most studio lights and strobes).
The effect in which the light is dimmer on the far side is called light falloff. The simplest way to see this effect is to take a picture of a road at night with a strobe as a light source. The area close to the strobe will be well lit and as the road gets further from the strobe it will get darker and darker, until it will become totally black.
This effect is also true in portraiture. When you are taking a portrait using only a key light (i.e. a single light portrait). Your subject will be more lit where the light is close and darker where the light is far.
In the picture below you can see how light falloff looks like. Notice that the light is bright on camera left and it falls off to camera right.
Image cc by Meredith Farmer
What Effects Light Falloff?
The distance of light from the subject:
The closest the light source is to the subject, the stronger light falloff you'll get. The Strobist uses this fact to discover if the light source was close to the subject when discussing how to reverse engineer lighting.
The size of light:
The larger the light source the more diffused the light it produces and the less light falloff you will experience. For example, a large softbox will produce less light falloff then a small softbox; a bare flash will produce more light falloff then a flash shot through an umbrella.
(Click here for a bigger size, and here for a super size)
Using The Light Falloff Card
When making this cheat sheet card, I wanted to explore the effect that a large light source will have on light falloff. The beautiful model on the picture is my wife, who kindly agreed to rid herself from two weeks of doing the dishes help with this exercise and.
The idea is simple, I took four lovely images, each one with a different flash to subject distance. The first image was taken with a very close flash to wife distance: 80 cm, I increased the distance 80 cm more for each shot.
You can also see the effect that a close by silver reflector had on the portrait.
On the top, you'll find the distance of the light from my wife's head. Distances are 80 centimeters, 160 centimeters, 240 centimeters and 320 centimeters. Under those columns you'll find a portrait done with a single light source, a companion portrait done exactly the same but with a reflector on the left, and a picture of the setup.
I hope it will help you plan your next shot.
Here are my conclusions:
- I have a beautiful and photogenic wife (no, offense, Yossi, your cheat sheet cards are OK too)
- As the book says, the further one takes the light source, the less light fall of one can expect.
- How far should you place the light source? That depends, but here are some ideas and thoughts that may lead to an answer:
(1) The furthest the light the less light falloff and less drama.
(2) If you increase the distance of the light source from your subject the light is getting "smaller" and harsher. This effect is only slightly shown in this exercise, but it will be more noticeable if you are using a smaller softbox.
(3) To create a really even light, you can use a close reflector. Then the reflector will provide softer light if the light source is closer.
The Making of the Light Falloff Cheat Sheet
Below you can see the setup I used to take the shots. At camera left, you'll find my wife facing an overwhelming softbox. (about 1 meter X 1 meter) the flash I used is a local brand called vLen 400, but it is quite similar to the older alien bees.
The image does not show it, but I places Gaffer Tape "X"s to mark the locations of the flash - this helped me to create repeatable results. (I got this tip from Pro Photo Life, see 1:05)
Another thing I have notices is that my ceiling is not high enough. This is why I went with side lighting and not classic Rembrandt lighting. I could have done Rembrandt lighting for the first two pictures, but as I got further and further, I had to raise the flash higher and higher, until I met the ceiling and could not keep proper lighting.
Spreading The Word
Like my other cards, I placed the Portrait Lighting Reflector Cheat Sheet Card under CC license. Feel free to download it, print it and spread it around. The idea is that you can use the collection to build better lighting.
If you have ideas on how to use this card differently, of you just want to say something about it hit me in the comments.
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Related:
- Portrait Lighting Cheat Sheet Card
- High Key and Low Key
- Measuring and Adjusting for Light Falloff
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Comments
thanks...
...for Your work.
Best regards
Greg
Great!
Really nice job as usual.
Simple and really useful, thanks!
Marcello
Great exercise
It really is good to go through the exercise of what light and different lighting situations offer. Thanks for sharing the cards, they are extremely valuable.
Rosh
http://www.newmediaphotographer.com
Thanks guys
I appreciate the positive feedback. If there are other cards you;d like to see, just let me know about it.
some thoughts...
Hey! Thanks for your continued posting on the DIY blog. I check it regularly.
A couple of things to consider with your post:
First, you don't mention, but I assume you are adjusting your light power (or aperture, or ISO) to get a proper exposure for each image. It won't be obvious to the beginner that the light needs to be cranked up when you move it further away, to achieve the same general exposure.
And with that in mind, one has to control for the rest of the room acting as a 'fill reflector' when you move the strobe further away. In a perfectly black room, this wouldn't be a problem. But in the real world, when you move your light further back, you have to boost the power (or change the aperture or ISO). This in turn makes the reflected strobe light from the walls and other sources more significant in relation to the strobe itself. So while you might get a 'harder' light source further away, the issue might get a little confused by reducing the light ratio…which can sometimes look like a softer light source was used.
This is evidenced by the silver-reflector series of shots. The contrast actually appears to be less in the 320cm shot, even though as a harder light source (because of the distance), one would expect more defined shadows. The reason of course is because the silver reflector hasn't changed its distance, and is more of a 'player' with the strobe being further away.
This is not to correct or dispute anything you've said, just more of a clarification. :)
Keep up the good work!
More Thoughts
Hi Matt,
Thanks for putting up those thoughts and idea. It looks like I am up for another challenge to try and eliminate any bounce from nearby walls.
I have to options for this:
1. use a really big studio (not really possible - you've seen my living room :)
2. try and use a flag to cast off any bounce from other places.
and actually there is a third option which is to shot in an open place. - I think this one will be the easiest. If I can get some external power I will definitely try this to make the card more complete.
Your assumption about the flash intensity is correct. as you can see from the setup shots, I pumped more and more power to the flash as I got it further away (otherwise, I had to change camera setting).
Nice tutorial
Hey, thanks for the photo credit and the use of my self portrait in your article. That photo was taken next to/under a lamp-shaded floor lamp at my parents house - no technical set-up by a long shot. ;-)
Your contact sheet lighting is beautiful. As is your (wife) model.
Self Portrait
Thanks Meredith.
I love your self portrait - it shows how well you can do with not pro equipment.
My wife says thanks :).
Thank you for your work
It's knowledge well laid out on the post. Thanks!
-joshua
If you've ever taken a
If you've ever taken a gander through my collection of photos on Flickr, you've probably noticed that I don't shoot many people, and when I do, it's normally candid photo work. There's a really simple reason for this: I don't find portrait work to be particularly easy, and I hate sucking. Still, I've been building up my arsenal of lighting equipment (Pocketwizards, a portable Manfrotto lighting stand, a couple strobes, Justin Clamp, a couple umbrellas, etc.), and slowly edging my way towards overcoming my fear of failing miserably. This fear of failure is, apparently, a pretty common problem. Henri Cartier-Bresson, the co-founder of Magnum Photos, once famously said: As you've probably noticed by now, I started a photography project on the 1st of the year where I shoot and post one picture every single day until the beginning of 2010. I decided to start off the year by shooting a series of portraits, in part because I want to overcome this fear of failure with lighting and portraiture, and because embracing Cartier-Bresson's maxim sooner than later means I can stop sucking that much more quickly. In any case, just blithely setting up some equipment and firing away won't mean I get better at my craft, so I always jump at the chance to get a good introduction to some aspects of this process that I might not otherwise have known about.
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