Author: David Halgrimson
Here is a little info on using extension tubes to get that super close shot.
An extension tube is used on a lens to allow for getting closer to a subject. It is mounted between the camera body and the lens. They come in many sizes, i.e. I have a 13mm, 21mm, 25mm and 31mm. They are hollow, no glass, and simply move the lens closer to the subject.
There are two types that I am aware of, those that have electronics which allows for auto focus and those without electronics. You can guess which is less expensive. Typically, manual focus will be used anyway as focusing becomes very sensitive the closer you get to the subject. The disadvantage of none electronic tubes is no adjustment for aperture unless the aperture can be set on the lens. The cost is very reasonable, a set of three starting around $40 and up unless Canon, Nikon or other brand names are preferred.
Extension tubes can be combined, i.e. a 13mm and a 25mm for a total of 38mm. The larger the mm of extension used the closer the lens can be to the subject. There is some light loss from using extension tubes and this will have to be adjusted for in the camera.
The use of a tripod when using extension tubes is almost a must as focusing becomes very tricky. Extension tubes are great for flowers, insects and any other small subjects.
I took these photos using the camera with no extension tube and then with 4 different tubes, 13mm, 21mm, 25mm and 31mm, I did not combine any. A Canon 5D mkII and a 24-105mm lens was used and the focus ring was set to the Macro area of the lens and ISO was 100 for all the images here. The camera was on a tripod and was not moved,
I started getting shadow on the subject the lager I went with the extension tubes so this is something to keep in mind. Also, focus was getting more difficult and DOF was getting very narrow, I did not try other aperture settings, this is another thing to be aware of. This was not an exact science experiment, I only wanted to show what an extension tube can do for getting those very close shots.
David Halgrimson is a trip leader with Arizona Highways Photo Workshops.