When shooting any close-up composition with your macro lens, or your Canon 500D close-up lens or extension tubes AND if within your composition there is a single or multiple light source in the distance, that light source will assume the shape of the aperture and record as out of focus spot of light. IF you wish to record perfect circle shapes of out of focus spots of light you MUST use the largest lens opening and depending on the lens you are using that may be f/4, f/3.5 or f/2.8.
In
addition to the very narrow depth of field that macro/close-up work is known
for, there is also another phenomenon about close-up work that most
photographers don't either know about or at the least, they fail to exploit
often enough. I am referring to what are called 'specular highlights'. Specular highlights are the out-of-focus hexagonal shapes that show up in the background and foreground of the single focused blade of grass you see here, (right); they are nothing more than out of focus dew drops, within which is the reflection of the sun itself. And when ANY out of focus spot of light is part of a close-focused composition, the out of focus spot(s) of light will assume the shape of the aperture opening of the lens. You will also see that the size of these highlights vary and that is because of the following: the closer you focus on a given subject, the specular highlight in the background will become larger and more diffused. So as you look at this dew-laden blade of grass, the larger out of focus specular highlights are simply other backlit dew drops that are further away from the focused blade of grass. Let's see how this translates into another creative technique that is at your disposal whenever those skies are clear at sunrise and/or sunset. As fun as it is to shoot dew drops on blades of grass, lets now take this idea of out of focus spots of light even further!
I know I don't have to twist your arm to shoot a sunset AND, if you get in the habit of also shooting a simple yet effective composition of a subject against an out of focus spot of light, (a single shaft of the sun's light) you will soon double your production of winning images.
It is during the last few minutes of sunset or the first minutes of sunrise where you have the opportunity to shoot directly into the sunset or sunrise light and record that single out of focus ball colorful of light.
In this wheat field landscape before me (below left), the sun is starting to rise and I have already picked my three stalks of wheat, holding them in my left hand. With my camera and 60mm Micro Nikkor on tripod, and with the addition of an FLW Filter , ( a deep magenta color that I often favor for sunrises and sunsets) I began to focus on the three stalks of wheat which I am holding directly out in front of the lens, directly in line with the sunrise taking place at the infinite horizon. Immediately, I see an out of focus ball of yellow light, (a shaft of light from the distant sunset) a welcomed contrast to the three-silhouetted stalks of wheat. To assure that I record a circular shape of the distant sunset light, and NOT a hexagonal shape, I have set my aperture to wide-open, f/2.8. All that remained was to adjust my shutter speed until a correct exposure was indicated and then shoot (below right).
This idea is NOT limited to the sun as any out of focus light source will perform in the same manner e.g. a flashlight, a match, a porch light, headlights and taillights, bright sunlight reflecting off of rivers and streams, even Christmas lights. And to better familiarize yourself with this optical phenomenon, let me suggest the same exercise to you that I recently did with one of my students, Eugene Almazan. Eugene was one of the participants in my Chicago On-Location workshops this past June. We were all shooting the Chicago skyline from North Beach when I suggested that Eugene turn around and take note of the parking lot street lamp that had just turned on.
It was then that I grabbed a nearby dandelion seed head and suggested that Eugene mount his 105mm Micro Nikkor lens and Nikon D300 to his tripod and set his aperture to WIDE-OPEN, (f/2.8 in this case) and following that, I suggested that he now hold the dandelion at roughly arms length and focus on the dandelion while also including the distant street lamp in his composition (below left). He was quick to exclaim, "WOW! It looks like a sunset is taking place behind the lone dandelion seed head!" And sure enough, as you can see here, (below right) it does indeed look like a big ball of setting sun is going on behind the dandelion seed head.
This idea is of course not limited to actual sunrises and sunsets, as you can clearly see even a lone parking lot street lamp can be a good substitute! Try this next exercise yourself and you will see exactly what I mean: Dim the lights in the dining room or kitchen and grab a flashlight, turn it on and lay it down on one end of a table, pointing it towards you where you have set up your camera along with your macro lens, or a zoom lens in combination with a Canon 500D close-up lens or with an extension tube. Now grab a fork or a straw or heck even a toothbrush which you have placed in a glass, and focus on the tongs of a fork, the straw, or the head of the toothbrush and what do you see? You should see an out of focus 'ball of light' directly behind your focused subject! And if you want to record that perfectly circular out of focus ball of light, you MUST set your aperture to wide-open. Okay, so what are you waiting for? Get out there in the real world and make this a summer to remember!