The majority of the macro shots I create are made a few hours after the sweet light of sunrise and a few hours before the golden glow of sunset. This entails having to deal with the strong contrast of late morning and early afternoon sun. During these times of the day, shadows are deep and highlights burn out. Whether you're shooting film or capturing the picture digitally, the contrast range exceeds what can be recorded. With slide film, the exposure needs to be based on the highlights which causes shadow areas to go dark. Digitally, two exposures can be made for first the highlights and then the shadows. The two can be blended in a computer which produces wonderful results, but this creates an extra step and is time consuming. I prefer an easier solution.
Diffusers are a simple and inexpensive answer to solving contrast problems when shooting macro subjects. Their purpose is to soften the source of light and eliminate harsh shadows and hot spots that would otherwise be eyesores in the image. When a diffuser is used, the light that's produced emulates the light of a bright overcast day. The light wraps around the subject which creates even tones and soft contrast. Studio photographers spend thousands of dollars on flash equipment and soft boxes to achieve this look to create portraits and product shots.
For use in the field for macro work, a diffuser can be very basic. If you're on a tight budget, an old shower curtain liner works fine. Other materials that do the job are white bed sheets, tissue paper, or an old white sun umbrella. As long as light can pass through the object and it doesn't add any color to the scene, it's a good candidate. Commercially made diffusers come in all different size diameters and can be had for under $50.00, even for the larger ones. The smaller they are, the more they drop in price. They're very convenient in that they have a unique way of collapsing by twisting the outer rim so they fold to about one fourth their overall size.
To use, simply place the diffuser between your subject and light source. Metering is straight forward in that all the tones become even. You'll see the results as you place the diffuser nearer or farther from the subject. Make sure the diffused area covers the background or else you'll wind up with gorgeous soft light on your subject and bright, out of focus distractions in the background.
