Chapter 7

Using Flash

7.1 Why Use Flash?

In the previous chapter we considered methods for achieving good exposures—that is, for getting images that are not too dark and not too bright.  By adjusting the aperture, shutter speed, and ISO setting, we can control the amount of light reaching the camera’s imaging sensor—up to a point.  On overcast days or in deep forest you’ll often find that there’s not as much light available as you’d like.  In order to achieve reasonable exposures in these situations you’d normally have to compromize either the noise level (by boosting ISO), the depth-of-field or lens sharpness (by using an extremely wide aperture), or the ability of the camera to freeze the bird’s motion (by using a slow shutter speed).  The use of flash—i.e., a brief pulse of artificial lighting—can both alleviate lighting constraints and in some cases provide an extremely effective means of freezing very fast motion (such as the rapid wingbeats of a hummingbird). 

Fig. 7.1.1 : In deep forest settings, flash is a necessity.  This mother owl and her baby
were lit from below by flash, producing far more detail, and better color capture,
than could have been done without the flash.  Note that the blue glow in the adult’s
eye is not an artifact of flash: she’s blinking her nictitating membrane.
(1/80 sec, f/4, ISO 800, TTL flash at -2/3 FEC w/Better Beamer, 600mm)

     The above image illustrates the value of flash in dim environments.  In this case I was photographing a mother owl and her baby beneath a dense forest canopy on an overcast day.  This image simply wouldn’t have been possible without the use of flash.  Even with the use of a wide aperture (f/4), a slow shutter speed (1/80 sec), and a moderately high ISO setting (ISO 800), a comparable image couldn’t have been obtained without flash, considering the low noise level, the sharpness and detail, and the color fidelity of the image that was captured using flash.  While it’s easy to propose that natural lighting should produce the most natural color, the real issue (assuming your purpose in photographing birds is to produce aesthetic images) is how to obtain the most pleasing colorskeeping in mind that our eyes see more color in direct sunlight than in shady ambient light.  Since flash units are typically calibrated to the same color temperature as noon sunlight (around 5700 degrees Kelvin), they provide a far better approximation to white light than does indirect sunlight, since indirect sunlight (what we call ambient light) carries with it the color biases that are imposed by the various natural surfaces off of which that light has reflected (or passed through, in the case of clouds or water vapor).  In short, since flash mimics the color distribution of pure sunlight, it’s much more suited to bringing out vibrant colors in bird plumages than the impure ambient light available in shaded or overcast environments.
    Another example of the color advantage of flash is shown below.  This figure shows two different birds, both warblers, shot on different days with different cameras and lenses (the bird on the left is a black-throated green warbler, and the bird on the right is a hooded warbler).  But the main contributing factor to the differences in lighting and color rendition is the use of flash for the photo on the left, and the absence of flash in the photo on the right.

Fig. 7.1.2 : To flash or not to flash?  The flash image (left) shows more detail and more vibrant
colors than the non-flash image (right).  Note the fine detail in the black throat patch in the bird
on the left, due to flash.  Finally, note that both birds have a catchlight in the eye
the one created
by flash, and the other a reflection from the ambience of the bright, overcast sky.

Notice in this example that while both birds have yellow and black heads, the yellow on the flashed bird (left photo) is much richer, and that even the black plumage shows fine detail in the flash image.  In contrast, the image on the right shows no detail whatsoever within the black part of the bird’s plumage.  The photo on the right is even overexposed, with the gray sky appearing almost white instead of gray, and yet the bird is still very lacking in detail and color as compared to the photo taken with flash (left).
    As we’ll see in the next section, flash tends in most cases to affect the luminance of the foreground far, far more than it does the background.  This often has the effect of making the subject (the bird) stand out more from its background than would occur without flash, and for bird photography that’s most often a desirable trait.
    Flash even has its uses in bright environments, as illustrated in the figure below.  Here we’re dealing with a bird that is extremely back-lit, meaning that the sunlight is striking the far side of the bird—i.e., the side of the bird that’s facing away from the camera. 

Fig. 7.1.3 : Flash in backlighting is a godsend.  The sunlight was shining on the far
side of the bird (and on a small portion of the bird’s back).  Full-power flash with a
flash extender allowed details in the underside of the bird to be brought out far better
than they would via ambient light alone.  (1/160 sec, f/6.3, ISO 125, TTL flash at +3 FEC).

In this case I was able to bring out a very considerable amount of detail in the bird’s right wing and on its chest and belly, which were not in direct sunlight.  Notice the fine details on the bird’s black legs, which were also fully shaded from the sun.  This bird was about 40 feet from my camera, requiring the use of very strong flash lighting to illuminate its darker features.  I accomplished this by turning up the flash to full power (actually, by turning up the flash exposure compensation
well get to that in section 7.5) and using a large flash extender; flash extenders will be discussed in section 7.9.
    Even subtle uses of flash can be very effective in improving a photo’s exposure.  In the twin images below you can see that one image has more shadow areas—and less detail—than the other.

Fig. 7.1.4 : Fill flash (right) versus no flash (left).  The fill flash has partially dispelled some
of the shadows, particularly around the eye and in the parts of the bird’s upper plumage facing
away from the sun.  Flash has also created a catchlight in the bird’s eye, though an off-center
catchlight would look better (this can be trivially fixed in postprocess).

The right image used what’s termed fill flash—meaning that flash was used not as the main light source for the scene, but as a subtle augmentation of lighting to dispel unwanted shadows.  These two photos were taken in rapid succession using continuous drive mode (discussed in the previous chapter).  For the image on the right, which was taken first, the flash fired properly, but when the camera took the image on the left just a fraction of a second later, the flash failed to fire because its capacitor wasn’t yet sufficiently re-charged.  Notice that the backgrounds are essentially unaffected by the flash, while many of the shadow areas on the bird have been illuminated by the flash in the image on the right.  Techniques for effective use of fill flash are discussed in section 7.6.
    Although flash can introduce unpleasant image artifacts in the bird’s eye (so-called steel eye, or red eye in some species), in some cases it can actually improve the rendering of the eye by adding a catchlight, as demonstrated by the image below.

Fig. 7.1.5 : Another example of a catchlight created by flash.  Note also the enormous
amount of detail in the white feathers (retaining details in pure white subjects is always a
challenge in photography).  Much of this detail is due to the
micro-contrast phenomenon
commonly produced by flash, which was explained in section 4.3.

The small, white spots in this eagle’s pupils are reflections from the flash, and while they may not perform an especially strong role in this particular image, for other birds (especially those with completely black eyes) a catchlight can make the difference between eyes that appear natural and those that appear dead.  Catchlights often occur naturally from direct sunlight, but when the sun doesn’t cooperate, an artificial catchlight (either from flash or drawn in later in Photoshop) can significantly improve an image of a black-eyed bird.
    One very significant benefit of flash, especially when used at close range on small birds such as warblers and vireos, is the effect that I call micro-contrast.  This phenomenon was described previously in section 4.3.  Although it can occur with natural sunlight, it’s more consistent and controllable when induced via flash.  The vireo image below illustrates micro-contrast quite well.

Fig. 7.1.6 : Another example of micro-contrast.  The individual feathers are visible in almost
all parts of this tiny bird’s plumage, due to the effect of flash.  Although sunlight can also create
micro-contrast, flash tends to do so more reliably and over more of the visible portions of the bird.
A small amount of steel-eye is visible in the lower half of this bird’s eye; this can be fixed in postprocess.
(1/1600 sec, f/8, ISO 500, TTL flash at -1 FEC, 800mm)

In the image above, micro-contrast appears via the minute feather details on the bird’s cheek, throat, chest, belly, and flank.  As explained previously, micro-contrast emerges when fine feather details are illuminated by light from a single direction.  Individual facets of a feather’s filaments (the rachis, barbs, and barbules) reflect light in different directions, depending on their orientation relative to the camera’s sensor plane.  Facets parallel to the sensor plane reflect back much more strongly than other microscopic features just thousandths of an inch away, resulting in an exaggerated degree of contrast between neighboring microscopic features on the bird, as seen by the imaging sensor.
    The kinglet image below gives another example of microcontrast.  Of all the ruby-crowned kinglet photos I’ve seen posted on the internet, most of them depict the bird as having a largely uniform beige color.  As you can see below, the bird’s plumage actually has quite a large range of colors.  While the unidirectional nature of flash light enhances the micro-contrast of the bird’s feather filaments, the use of stronger lighting—and lighting with a more neutral color temperature than that of ambient light—results in more subtly discernible color gradients than would otherwise occur.

Fig. 7.1.7 : Yet another example of micro-contrast.  Capturing this level of detail in such
a tiny bird (a ruby-crowned kinglet) requires high magnification and good lighting.
The lower catchlight and small amount of steel-eye can easily be removed in postprocess.
The upper catchlight is likely from ambient light.

    A final advantage of flash that we’ll consider in this chapter is its ability—when used properly and in the right conditions—to freeze fast motion.  Many novice photographers don’t realize that the duration of a single flash pulse can be much, much faster than the fastest shutter speed on an SLR camera, and that freeze-frame images of hummingbirds and other fast-flapping birds are typically obtained using flash to freeze the bird rather than a fast shutter-speed.

Fig. 7.1.8 : Freezing a bird’s wings via flash.  Although theres still a lot of motion blur
in this bird’s wings, without the flash it’s doubtful the wings could have been frozen as
well as they were.  This shot was not planned: if you take enough photos of warblers
you’re likely to get a few with the wings spread like this, by sheer luck.  Note that the
background of this image was replaced via Photoshop.

In this chapter we’ll consider all of these advantages of flash photography, and we’ll show in detail how they can be used to improve your ability to capture stunning images of wild birds.