Field Guide 101: Clos-ups with Extension Tubes

Monarch butterfly, Danaus plexippus

Natural Bridges State Park, 2007

Sometime in October of every year the Monarch Butterflies start arriving in Santa Cruz at Natural Bridges State Park, the Monarch Butterfly Natural Preserve, and feed upon the abundant Milkweed plants in the area. They don't start to cluster in the groups until later in the year at which point they will reproduce and die. This yearly cycle creates an endless source of photographic opportunities, the most obvious being macro photography.

I own the excellent Canon 100mm macro lens but it doesn't have the working distance often required for such skittish creatures. When working with butterflies you have two choices: Wait for one to land within your photographic reach or watch for one landing and sneak up on it. I use both approaches. When I'm waiting typically I'm using a tripod and a very large lens as was the case with the photo above. It was taken early in the season just as the Monarchs arrived in town. I used a 500mm lens with a 1.4x extender to get an effective focal length of 700mm on a Canon 5D. I then turned this 700mm lens into a super macro lens by adding a 20mm extension tube. The extension tube reduces the minimum focal distance so I can maintain a working nice working distance but get close enough to fill the frame with a butterfly.

Kenko Extension Tube Set



An extension tube is simply a tube with lens mounts on either side that mounts between the lens and camera and is designed to move the lens farther from the film or sensor. By moving the lens farther away from the film or sensor the focus distance is reduced effectively turning the lens into a macro lens. Actually the focus plane of the entire lens is moved closer so not only is the minimum focus distance less, but the lens can also no longer focus to infinity. The longer the extension tube the closer the minimum focus distance becomes. Extension tubes are just a tube with no optical elements so the quality of light is not degraded but the amount of light is reduced. Most extension tubes sold today have electronic contacts so the lens can auto focus but the loss of light may make auto focus difficult in low light conditions. Usually the light loss is a stop or two.

When I'm not patient enough to play the wait game I put a 20mm extension tube on my Canon 100-400mm or 70-200mm lens and use my Canon 1D Mark II for it's increased auto focus performance when at f/8.

I personally prefer to use extension tubes on a telephoto lens as opposed to a dedicated macro lens such as the Canon 100mm or 180mm for three reasons:

1. None of the macro lenses have Image Stabilization.
2. I prefer to have a general purpose lens in my bag that can be used for more than just macro work. This is really important when traveling or hiking when weight really matters.
3. The macro lenses are slow to auto focus and when working with small critters you need all the speed you can get.

When I was staring out I wanted to shoot small things and asked a friend what to get and he suggested extension tubes. I went out and bought the Canon 100mm macro lens because it seemed to be more of what I wanted. Looking back, I wished I had bought something like the Canon 70-200mm f/4 and some extension tubes. This would cost a bit more but there are many more photographic possibilities with this equipment.