Right after finding out that you should always take the lens cap off before taking a picture, the second most important lesson in photography that we usually learn is that we should not point the lens against the sun. There is a very good reason for this: the camera’s light metering system will attempt to compensate for the direct sun’s light intensity by dramatically reducing the exposure time, which in turn will render all other objects in the frame severely underexposed. (Or, if you use a telephoto lens, you can blind yourself.) We all have seen crappy pictures of people standing on the beach at sunset, rendered as muddy silhouettes against a dimly lit sky, despite the fact that the scene appeared vibrant and majestic to the person holding the camera. This is because cameras are not equipped with the most powerful of all computing machines, the human brain, which can not only record a scene, but also interpret it and selectively adjust its light parameters.
But there are ways of compensating for the seemingly overwhelming intensity of direct sunlight, and shooting against the sun is not as difficult as many photographers think. The glowing orb of our nearest star can be incorporated in many compositions, including macro shots of insects and other small organisms, with only a bit of preparation.
The first and most important rule for shooting against the sun is to make sure that your lens is clean. I mean, really, really clean. Because even the tiniest smudges, specks, or scratches will cause a tremendous amount of ugly diffraction and flare, which can ruin a beautifully composed scene. These optical aberrations are often difficult to notice through the viewfinder.
Secondly, you may need to use a source of “fill-in” light to help illuminate the object in the foreground. In most cases this will be a flash, but you can also use a collapsible silver or gold reflector (such as this one). I say “may need to” because you can position your subject in the frame in such a way that it sits directly in the path of the sunlight, blocking the most intense part of it. If the subject (e.g., a flower, a butterfly) is thin or translucent enough, the light filtering through its body will be sufficient to properly illuminate it. In most cases, however, a “pop” of flash will be needed to counterbalance the sunlight.
Exposing for shots against the sun is a little tricky. In my experience it is easier to use fully manual exposure controls, rather than using the camera’s automatic settings, such as the Aperture Priority. The easiest way to do it is to measure the exposure time by pointing the lens at a point close to the edge of the sun, but not the sun directly. Take a photo and see how the sun is exposed: its center should appear slightly overexposed, but its edges should not. Once you have found the correct exposure settings for the sun, add the counterbalancing light. Again, I would suggest using a flash in the manual mode, and adjust its power incrementally until you find the right intensity. It goes without saying that it is much easier to fine tune the exposure settings for subjects that are not particularly agile. Thus, I would suggest to practice the exposure adjustments on inanimate objects, such as branches or flowers, before you attempt to photograph a running beetle against the sun.
It is easier to shoot against the sun later in the afternoon, when the sun is low on the horizon, and its light intensity is lower. Late afternoon/early evening light will also add to the overall atmosphere of the scene.
Nearly any lens can be used to shoot against the sun, but this approach works really well with wide angle lenses. This is because it is easier to fit both your main subject and a large portion of the sky into the frame, which in turn means that the sun itself does not dominate and overpower the scene. At the other end of the spectrum, really long macro lenses (150mm and more) can also be used, and their benefit is that the sun will appear larger in relation to your subject; they may, however, require a more powerful source of the fill-in light.