Correct vs. Creatively Correct Exposure
o doubt, you may have already discovered that the slightest shift in point of view can change the point of focus dramatically in macro work. So can the aperture choice. For this reason, I want to make one thing perfectly clear: There is a correct exposure, and then there is the creatively correct exposure. Every picture-taking opportunity—whether you’re shooting close-ups or not—offers up no less than six possible combinations of apertures and shutter speeds that will result in a technically correct exposure. Yet, more often than not, only one, or possibly two, of these combinations will be the creatively correct exposure.
Is there a way of knowing before you take the picture which one exposure is the most creatively correct? Yes, if you use an important feature found on many SLRs and DSLRs: the depth-of-field preview button. I’ll get to that on the next few pages, but first take a look at these three images to see how important aperture is.
WHAT’S NOT SHARP IS JUST AS IMPORTANT AS WHAT IS
Distance and aperture play huge roles not only in what records as sharp on the charge-coupled device (CCD) or on film but also in what doesn’t record as sharp. Knowing this, exploit the background when shooting close-ups. A simple change in the sharpness or blurriness of the background can affect the final image in a profound way.
All three of these images are exactly the same exposure, meaning the quantitative exposure value of each aperture and shutter speed combo is the same. However, you can clearly see that, visually, they are each different. The first image was taken at f/5.6 for 1/500 sec., the second at f/11 for 1/125 sec., and the third at f/22 for 1/30 sec. Again, their quantitative value is the same, which is to say that the volume of light that hits the sensor (or film) is the same. The difference can be seen in the effect on the background: In the first image, the background is limited to subtle out-of-focus tones and no distinct shapes. In the second, the background begins to offer up a bit more information, and by the third, it’s clear that the background consists of other nearby flowers. All three are a correct exposure, but as is often the case, only one or sometimes two are the creatively correct exposure. (Note that I took all three photos with my Nikon D2X and Micro-Nikkor 200mm lens on tripod.)
Top image: f/5.6 for 1/500 sec.; bottom image, left: f/11 for 1/125 sec.; bottom image, right: f/22 for 1/30 sec.