Every lens has a minimum focusing distance: the closest point where the lens can get a sharp focus. Generally, the longer the focal length of the lens, the greater the minimum focusing distance.
Most of the time, this distance isn’t too important: with longer lenses you’ll generally be photographing a distant subject, because you just can’t get close to it.
But, sometimes you can get close to your subject and you’ll want to use a long lens to get that great bokeh (a result of the narrower angle of view). Good examples of this include wildflowers and butterflies. In these cases, to fill the frame with your subject, you’ll usually need to focus closer than that minimum focusing distance.
So, how do you make your lens focus closer?
Solution: use an extension tube
An extension tube (pictured above) is a pretty basic piece of equipment: it’s just a hollow tube that extends the distance between the lens and the camera’s sensor. The more you increase this distance, the closer the lens can focus.
Extension tubes come in a variety of different sizes, from 12mm to 50mm, but the 25mm should be suitable for most cases. For example, if you put the 25mm extension tube on a Canon 70-200 F/4L lens, you can change the minimum focusing distance from 4.9 ft to about 4 ft! This 1 ft difference may not sound like much, but test it out in the field, and you’ll surely be glad you have that extension tube.
You can also use an extension tube as a cheap way to turn your 50mm lens into a macro lens. If you add a 25mm tube to that lens, you’ll end up with 1/2X magnification (where a true macro lens would be 1.0X). As a rule, magnification equals the total extension divided by the focal length of the lens.
Where to buy extension tubes
Most camera stores carry extension tubes, but please feel free to support PhotoNaturalist by purchasing them through our B&H affiliate link (we earn a small commission through each referral). I purchase about 90% of my equipment through B&H because of their great selection and service.
If you use a Canon, you can save some money by purchasing the Kenko tube instead of the Canon one. I’ve been using the Kenko C-AF Uniplus Tube for awhile, and it works great!
I’ve heard the Kenko tube for Nikons causes vignetting, but I can’t confirm this (I just have a Canon). So, to be safe, I’d just get a Nikon tube.
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About the Author: Steve Berardi is a naturalist, photographer, computer scientist, and founder of PhotoNaturalist. You can usually find him hiking in the San Gabriel Mountains or the Mojave Desert, both located in the beautiful state of California.
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Great article. You should write how you attach the extension tube to your camera.
Love the ‘tubes … I use the Kenko 36mm with my Nikon cameras/lens and it works fine. No problems with any lens I have used … 20mm, 50mm, 105mm macro, 18-55mm, 18-200mm, or the 80-400mm (haven’t used it with my 12-24mm – for that I use the shorter 12mm tube).
No worries. I have even tried it with my 1.7X converter …
Nikon and Kenko work fine together as far as I can see over the past dozen years or so I’ve used them.