“The art of art, the glory of expression and the sunshine of the light of letters, is simplicity.” – Walt Whitman
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I was asked recently by a relatively-new amateur photographer, “Why use flash?”
He was mainly shooting photos in locations where there was plenty of ambient light available to make a proper exposure with his camera, and I suspect that the unspoken subtext to his question was that he was wondering if there was any particular reason for him to spend the money to buy an external flash for his camera (or even to use the built-in “pop-up” flash).
Here’s what I told him:
There are two main reasons for people to use flash when making photographs:
- There’s not enough ambient light to make a photograph without flash, or
- The ambient light that’s there is not to your liking, and you want to modify or replace it with “good” light of your own.
Most beginners only think of reason #1. (It’s dark, so I use flash.) Simply adding more light quantity, without giving consideration to its qualities (such as its hardness, color, direction, and relative brightness), typically results in the dreaded “person in a dark cave” portrait.
A more experienced photographer will use flash to supply the light that he wants, where and how he wants it, either alone, or in addition to the existing ambient light.
Personally, I use flash most often when I’m shooting outdoors, in full sun, which is a situation where most amateurs wouldn’t even consider using flash at all.
In full sun, you have plenty of light, but it’s almost always very hard (the sun may be huge, but it’s 93 million miles away, and casts very hard-edged shadows). Also, full sunlight rarely comes from a flattering direction; it’s almost always overhead, which gives people raccoon eyes, and hides their faces in shadow if they’re wearing a hat. Also, full sunlight gives your images more contrast than any camera can capture in a single frame.
Adding flash from my camera position allows me to fill in those shadows without erasing them completely. This way, I can reduce the contrast in the scene to the point where my camera can actually record detail in the shadow areas, and I can avoid raccoon eyes and see people’s faces up under their hat brims. The flash also adds a bit of “sparkle” to the eyes, in the form of a “catch light” reflection.
Outdoors, I’m not generally looking to overpower the sun with my flash. I usually prefer to use flash that doesn’t call attention to itself. Instead of making the scene look “artificially lit”, I simply tame the shadows, and bring them under control.
It all boils down to control. Using flash, you’re able to take control of the lighting in your images, and are no longer at the mercy of the ambient light. To a photographer, that’s a very good thing.
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A recent discussion thread on the Strobist Flickr group did something that Internet discussions frequently do: it diverged rapidly from the original topic, and devolved into an argument over terminology.
The argument centered on the made-up term “light depth of field”. (For the record, I find this term silly; even worse, I find it misleading. I won’t be using it again, and I suggest that you forget it was ever mentioned.)
The context of the discussion, however, is both useful and instructive to examine. The key issue in that context is:
Given the inverse square law, how do you determine the minimum distance away from your subjects to place a light, in order that the exposure variation across those subjects due to falloff stays within acceptable limits?
It sounds complicated, but it really isn’t. There’s a smidgen of math involved, but it’s nothing harder than very basic high school algebra.
For those who’ve forgotten, let’s go over the inverse square law:
The intensity of light falling on a subject at a certain distance from a light source is inversely proportional to the square of the distance from the light source.
In layman’s terms, when you double the distance, you get the light intensity. Triple the distance, you get
the light intensity. Move n times further out, you get
times the light intensity.
We photographers like to deal in “stops” of light. Each “stop” is a doubling or a halving of light intensity. Put in math terms, the intensity difference in stops is the base 2 logarithm of the ratio of the intensities in foot-candles or lux.
And now, a little bit of high-school math:
Don’t worry — I’ll do the math for you. You can feel free to skip to the end, if you just want the answer….
First, we describe the setup. We have a light source (“L”) that is a certain distance (“x”) away from the closest subject (“C”). A second subject (“F”) is further away. How far? Subject F is “y” distance past subject C.
Something like this:
L -------------------x----------------- C ----y----F
So, the distance from L to C is x, and the distance from L to F is (x+y).
If a light intensity falling on C (“x” distance units away from L) is “i” lux, then that same light falling on F at “x + y” distance units away has an intensity of , which is a change of
stops.
We’re looking to find out how far away to put our light in order to get the light falling over our subjects to be even within a certain number of stops, when the group is spread out over a certain distance from the closest to the furthest subject. In other words, we’re looking for “x”, given the number of stops and “y”:
If y is a positive number (which it will be, as we’ve laid out the diagram), then the number of stops will be a negative number, indicating that the light is getting dimmer the further away that we go. While mathematically accurate, most photographers aren’t used to be thinking in negative numbers. To make the equation more useful, let’s flip the fraction over, which will reverse the sign on the logarithm. That way, we can specify the number of stops down as a positive number, rather than having to think of it as a negative number of stops up.
Now, we just need to solve for “x”.
And, finally….
There is our answer. It’s a bit ugly, but it’ll tell us what we need to know.
If the closest subject and the furthest subject are y feet apart, and we want the exposure across the group to be consistent within “stopsdown” stops, we can calculate the distance x in front of the group at which to place our light.
As an example, if we want at most a variation of 1 stop from front to back across a group of people, and the distance between the closest and furthest people is 3 feet, then our light has to be approximately:
in front of the group.
If we want to limit ourselves to 1/2 stop of variation across the same group, we need to place our light further away:
in front of the group.
The Bottom Line:
The further away your light source is from your group, the less variation in light intensity you’ll have across the group due to falloff. The overall intensity will, of course, be lower. That’s not in question. However, the important thing to remember is that there will be less variation of intensity across the group. You’ll have more even — although dimmer — light.
If you know how much variation in light intensity you can tolerate (in stops) and you know the size of the group (from front to back, as seen from the perspective of your light source), then you can fairly-easily calculate the minimum distance to your light source.
To make this easy for those of you without a scientific calculator, I’ve pre-calculated a few factors that you can use in the following equation, just by multiplying:
| # of stops | factor |
|---|---|
| 2 | 1.00 |
| 1.5 | 1.47 |
| 1 | 2.41 |
| 2/3 | 3.85 |
| 1/2 | 5.29 |
| 1/3 | 8.17 |
| 1/4 | 11.05 |
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The photos from NSL 2011/ROCstock 33 are now online for your viewing and purchasing pleasure. Click on the “Browse and Buy Photos” button in the left sidebar to get to the CrayonPhotos.com online store.
If you are one of the people who won a free 8″ x 10″ print in one of the raffles held during NSL/ROCstock, please contact me via email with your address, and the number of the picture you’d like to receive as your free print. (When you’re looking at the preview of an individual image, the picture number appears right underneath it, in the format “NSL11-xxxxxxxx”.)
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National Association of Rocketry President, Trip Barber, presents a plaque to Rocketry Organization of California President, Rick Dickinson, in appreciation for hosting NSL 2011.
After five days and four nights in the Mojave desert, I’m back home, and recovering from one of the best “working vacations” that I’ve had in quite some time.
As I mentioned in my last post, I was on-site at the NAR‘s National Sport Launch in Lucerne Valley, CA, this past weekend. I arrived last Wednesday evening, and didn’t get home until nearly 9:00 PM on Sunday, exhausted but happy.
I did, however, leave out one small detail that many of my readers are probably already familiar with: I’m actually the current President of the Rocketry Organization of California (ROC), who were hosting the event.
Rocketry is my hobby, and I’ve been an active member of ROC for well over a decade, now. As in most hobbies, there are clubs, and the folks who hang around and help out with the clubs’ activities over time tend to get handed more and more responsibilities. I’ve been on the ROC board for a while, now, and last year, they voted me in as President. It’s a lot of work, but very rewarding.
In any case, that explains the picture at the start of this post. I was very pleasantly surprised by Trip Barber, the NAR President, on Sunday morning, when he took the microphone at the launch control table, and called me up to present me with a plaque in recognition of my role as Event Director for this year’s NSL. It was a pleasure doing it, and the thanks really ought to be shared among a large number of volunteers. (But, all the same, I’m going to keep the plaque myself!)
I have just started to process the many photos I took at NSL, and I’ll post them in my online store as soon as I’ve gone through them, probably in about a week or so. In the meantime, here are a few liftoff shots to whet your appetites:
Liftoff of Jim Wold's "Naked Fat Man" rocket on a Kosdon by Aerotech K700 motor.
Veronica Kirk's Level 2 Certification Flight Lifts Off
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- Rocket launch at Lucerne Dry Lake
Come join CrayonPhotos.com at the National Association of Rocketry‘s annual National Sport Launch this coming weekend, June 10-12, 2011, in Lucerne Valley, CA, where we’ll taking pictures of amateur rocketeers and their rockets.
Hosted by the Rocketry Organization of California (ROC), this three-day event brings together young and old rocket flyers from all over the country. There should be over a thousand people gathered over the weekend in the middle of Lucerne Dry Lake’s vast flat expanse. FAA approval has been granted to allow rocket flights up to 19,000′ above ground level, so expect some spectacular sights.
We’ll be posting pictures from this weekend’s festivities once we get back in town, so if you can’t make it out in person, please check back next week to see what you missed!
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I’d like to offer my sincere thanks to all veterans for their service. You put your lives on the line so that the rest of us can enjoy the benefits of freedom. We don’t thank you enough for your service, and for that I apologize.
Thank you, again, for being willing to make the ultimate sacrifice. You honor us with your service.
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Wedding photography is an interesting specialty, which can really separate the pros from the amateurs. As always, what’s behind the viewfinder is the most important piece of equipment (your brain!).
But, with the number of naive photographers with their first DSLR who seem to see wedding photography as an “easy way to make some money” with their brand new camera kits, I thought it made some sense to look at the minimal entry requirements, from a camera equipment standpoint.
Weddings combine the technical aspects of fashion and portrait photography with the high pressure and tight time-lines of corporate event photography. You have to produce elegant portraits of brides in delicate white dresses standing next to grooms in black tuxedos, while preserving detail in both, under challenging (and often variable) lighting, and working on-the-fly with no chance for a re-shoot.
Continue reading “Equipment for Wedding Photography” »
If you read any of the camera review web sites or magazines, you’ll see that a lot of noise is made over noise. From the articles I’ve read, it seems as though if you can’t shoot black cats in coal mines without flash and get perfectly clean, noise-free output, then your camera must be junk, and you need to rush out right now and spend multiple thousands of dollars to buy the next generation of über-camera before everyone else notices what an amateur hack you are.
Guess what? They’re wrong. All that noise about noise is, as Shakespeare put it, “full of sound and fury, signifying nothing.”
If you were to consider all of the many factors that go in to making a photograph that grabs your attention and draws you in, and rank those factors in order of importance, “absence of noise” would never even make the top 10.
Continue reading “Your camera doesn’t matter.” »
