In last week’s post I discussed my progress through the
Strobist.com L102 lesson on position. This is the first of seven ways to control
light. The takeaways from this lesson
were:
- By altering the angle of our light source we can control how highlights/shadows are cast upon a subject.
- By altering the distance ratio between our subject and the flash versus the background and the flash we can control the exposure of the subject and the background independently.
This week I’ll be discussing Strobist.com’s second way to
control light apparent light size. This lesson begins with an exercise that
illustrates the effects of altering the apparent size of a light source and
then gets into a discussion on Specular Highlight Control. Hopefully by the end of this post that last
term won’t sound so foreign and complicated.
The first exercise instructs readers to take a series of
photographs while changing the apparent size of a light source. Please note that there is a major difference
between simply the size of the light source and the apparent (or relative) size of the source. When thinking about the apparent size you need to think about the size of the light source
from the subject’s point of view. Ask
yourself how the subject sees your light source.
For instance, a speedlite might look huge to a matchbox car,
if it’s close enough, but tiny to a full-size sedan. To get the same effect on a full-size sedan
as the matchbox car, you just need to use a light source that is slightly
larger than the car. Sounds easy,
right? In my Headshots post I discussed
bouncing a flash off a wall or ceiling.
Instead of using a car sized flash you could use a room sized ceiling to
bounce a small flash off of. By bouncing
the flash off a ceiling the car would see the entire ceiling as the light
source. Other ways to modify the size of
a light source include umbrellas, softboxes, reflectors or any number of things. When using these, the subject is no longer
seeing the relatively small speedlite as the light source but the entire
modifier as the light source.
 |
| Using a bare speedlite |
 |
| Using a shoot-through umbrella |
The bare flash in the first shot
was an apparently small light source
that creates a harsh shadow. This is
referred to as hard light. The umbrella used in the second shot diffused
the light over its entire surface making the area between highlight and shadow
much larger. This, photographers refer
to as soft light. It’s
important to remember that whether a light is hard or soft has nothing to do
with how powerful the light is but rather the apparent size of the light source.
The apparent size
of a light source also depends largely on distance. In the last example I kept the distance between
the pumpkin and the flash constant. Now
try to visualize what would happen if I used that same shoot-through umbrella
but instead of being two feet away from the pumpkin the umbrella was, say fifteen feet away. Would the umbrella still be an apparently large light source?
To help answer this question, think of the largest light
source you can think of, the sun for instance.
We know from elementary school that the sun is incredibly large (and
powerful), but on a clear sunny day it casts harsh shadows. How can this possibly be!? It’s because the sun is also incredibly far
away. This principal is the same for
your speedlite, the farther away it is the smaller it is, and the more powerful
it needs to be. Now on a cloudy day you
get much better shadows. This is because
the clouds are diffusing the sunlight making the entire sky your light
source. You can think of a cloudy sky as
giant shoot-through umbrella. This
diffused sunlight also improves color saturation. So go out and have fun when the sun is
shining, but when the clouds roll in, go grab your camera.
Up close the umbrella makes a huge impact compared to the
bare flash. When that umbrella is moved
out to a much greater distance the umbrella doesn’t make the light source apparently much larger. It’s really just robbing power out of your
flash so at a large distance you might think of ditching the umbrella.
As part of this exercise, Strobist.com instructed us to use a
fruit, of our choosing, to be the subject of this exercise. I typically work through these exercises a
week or two before my post discussing them is published. This means that even though this post is
published in November, I was working through the exercises in late October so I
felt using a pumpkin was fitting. I
realize I failed to follow one of the easiest instructions of the exercise by
choosing a pumpkin as my subject but it just seemed right at the time. I also learned this week that a pumpkin,
believe it or not, is a fruit. Now I feel like I’m just making shit
stuff up. I also no longer think I have
a clue as to what a vegetable is.
Most speedlites also have a zoom function, so I wanted to
debunk a misconception that you might have on how this effects the apparent size of the
speedlite. Let me show you an example of
how this works.
 |
| Flash at 24mm zoom |
 |
| Flash at 105mm zoom - no change to apparent size |
There isn’t much because the
zoom function of the flash does nothing to the apparent size of the flash.
At 105mm I’m wasting much less light outside the frame so I need less
lighting power but the size of the light source remains
constant. You can see that the second
photo is slightly brighter over all because of this. Please ask questions in the comments section
below if this explanation has left you confused.
Now let's get into Specular
Highlight Control. This is a pretty
scary term, at least it was to me, but hopefully it won’t be once we are
done. A specular highlight is the light
reflecting directly off an object into your camera. Look again at the last shot of the pumpkin. That reflection of the light off the left side of the pumpkin is the specular highlight. You can control the specular highlight by the
position of the light source and/or by modifying the shape and size of the light source by using an umbrella, softbox, etc. To illustrate this control I used a billiard
ball. It is highly reflective so it is
easy to see changes to the specular highlight.
 |
| Bare speedlite |
In the first shot I used a bare flash and you can see that
small light source reflecting off the ball.
I modified the light source in the second shot by using a shoot-through
umbrella. You can clearly see the
reflection of the umbrella on the billiard ball. These are specular highlights. These highlights can be modified by modifying a light source.
 |
| Shoot-through umbrella |
That’s it, that’s the specular highlight and a couple ways to
modify it. It’s not so scary now, is
it?
To play around with this more I took
a third shot of the billiard ball.
Can you tell what the light source is, how many there are,
and what I’m using to modify them?
Instead of just telling you the answers straight away I’d like you to
take another look at the photo and let me know what you think the answers are in the comments section below. Reverse
engineering how other photographer’s photos were made will help you when you’re
planning your own shoots. I’ll let you
know in my next post how this shot was created.
There are two upcoming assignments
in the L102 coursework. The Position and Apparent Light Size lessons include exercises that illustrate these controls. The exercises are not designed to create
great photos to hang on a wall. They are designed to allow you to play around
and learn the controls in a practical way.
Assignments are focused on refining
your skills to produce a finished product.
In my next post I’ll be discussing my progress through the Cooking Light and Umbrella Specular assignments.
You can preview these assignments on strobist.com, here, for a sneak peek at the goals of these assignments.
Until then, try these exercises out for yourself and
continue having fun with your camera.
I’m always excited when I finish a blog post because it means that I can
go shooting again! Don’t forget to add
any questions you have in the comments section and let me know how you think I
created the last photo of the billiard ball.
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