The
human eye can perceive
a contrast ratio of 800:1;
the best slide films,
30:1; and the best digital
sensors,
40:1. So photography
has always been about
compromising.
When shooting slide films,
the old adage was “expose
for the highlights, pray
for the shadows.” With
digital, that has changed
a bit, especially with
RAW files.
You can process the RAW
file two (or more) different
ways and combine these
images using an image-editing
program to get the best
of each exposure. When
shooting with a digital
camera in the RAW format,
you have the capability
of processing your image
specifically for different
exposure values, highlights,
midtones and shadows. You
can use this flexibility
of the RAW format to your
advantage when photographing
scenes with a high dynamic
range of light.
Is it best to slightly
underexpose or overexpose
RAW images? When you
lighten a dark RAW image,
you risk
adding a lot of noise
to the shadow areas.
When
you darken a light RAW
image, you might not
have good highlight detail.
I find when shooting
under
contrasty light that
it helps to slightly
overexpose
the image and then process
it twice—once to
have more shadow detail
and once to bring back
the highlight detail.
The image shown here
is from the wonderful
light
show at Chicago O’Hare
International Airport
in the tunnels between
terminals.
I had a four-hour layover
at the airport, and being
a photographer, I appreciated
the neon lights that
played around the moving
walkway
that connects the different
concourses, so I decided
to photograph them. I
rode back and forth on
the walkway,
shooting many different
exposures at many different
shutter speeds.
That’s one great
thing about digital—using
the image review on the
LCD, I could check the
shots and look for such
things as the highlight
warning to make sure I
wasn’t overexposing
the bright highlights.
I placed the highlights
just on the verge of
overexposing so that
I could keep the
overall photo bright
while still retaining
detail
in the highlights.
When I returned home, I
processed the image in
Adobe Camera Raw, built
into Photoshop CS2. Photoshop
CS2 is the first version
of Photoshop that allows
you to open two copies
of a file with the same
name, which makes this
technique easier. Otherwise,
when you first open a processed
file, you have to rename
it before you can open
a newly processed image
from the same file.
(STEP
1) Process
For Highlights. The
first time I processed
the
image, I moved Exposure
down to a minus number
to bring the overall
exposure down about a
half-stop. I watched
the bright colors to
make sure I held all
the detail and color
in the brightest areas
of the picture. The darkest
parts of the photo are
unimportant at this point.
I opened this version
into Photoshop.
(STEP
2) Process
For Shadows. I went back
into Camera Raw and processed
the image a second time.
This time, I opened up
the shadows by moving
the Shadow slider to
the left (which reduces
its setting) and by adjusting
the Exposure slider to
the right. This processing
step is purely about
the dark areas, so having
the bright colors lose
detail didn’t matter.
You may find, as I did,
that when the shadows
are opened up like this,
they appear a bit flat.
I added a little contrast
to the image because
of that. I also opened
this version into Photoshop.
(STEP
3) Create
A Layered Image. Now you bring
the two processed images
together into one file.
Since they come from
identical files, they
will match exactly. I
put both images side
by side in Photoshop.
Using the Move tool and
holding down the Shift
key, I clicked on the
lighter image and dragged
it in perfect registration
onto the darker image
(the Shift key keeps
them aligned). You must
move your cursor completely
onto the second photo
or you’ll get an
error message that says
you can’t move
the background layer.
The result is a file
with two pixel layers,
the light image over
the darker image. You’ll
find that some photos
do better with the darker
image over the lighter
image. There’s
no absolute rule for
this, though often it’s
best to put the image
needing the least amount
of work on top.
(STEP
4) Add
A Layer Mask. I then added a
layer mask to the lighter
image layer. The easiest
way to do this is to
click on the Layer Mask
icon on the Layers palette
(the icon is a rectangle
with a circle inside
it). This creates a Reveal
All (white) layer mask
on the active layer (you
also can go to Layer > Layer
Mask > Reveal All).
The secret to all masks
in Photoshop is that
black hides the layer
and white shows the layer.
At this point, all the
pixels of the lighter
layer show because the
layer mask is white.
(STEP
5) Bring
In The Lower Layer. To
show the darker pixels
of
the layer below, you
need to paint with black
on the mask to hide the
pixels of the lighter
layer. In this case,
I needed to balance the
bright lights along the
top of the photo with
the darker bottom area
of the image and I also
needed to bring in the
better highlights of
the underlying layer
to blend into the upper
layer that had the good
dark tonality. I used
the Paintbrush with black
as the foreground color
in order to paint with
black on the upper
portion of the mask.
With the layer mask active
(click on the mask to
make sure it’s
active), I selected a
soft brush with a fairly
low opacity; I recommend
20% to start. Then I
painted over the image.
I built up density by
going over some areas
multiple times. If you
just drag your cursor
back and forth across
the image, you won’t
be able to build up any
more density than the
20% opacity you set.
By releasing the mouse
or raising the pen (on
a tablet) as you go,
you can build up density.
If you use a soft brush
and build up the density
of your strokes, it’s
easy to make the blends
seamless.
(STEP
6) Refine
Your Layer Mask. You can see
your mask by Alt/Option-clicking
on the Layer Mask icon.
From the screenshot shown
here, you can see that
the edges of the mask
were refined and blended
to make the two photos
go together better.
Once the mask was complete,
I had an image that showed
good detail and contrast
throughout the image,
balancing the exposure.
So what was once difficult
to record in a single
exposure is now possible.
With one click of the
shutter, you can record
the information needed
in a RAW file, which
you can process in different
ways to bring out better
detail in both the highlights
and shadows. Then it’s
a simple matter of combining
the two images by using
a layer mask to make
your picture more closely
resemble what your eye
could see instead of
what technology can record.
It opens up many possibilities
for capturing reality
in a way that was never
before possible. |