Fun and Limitations with Extension Tubes: Macro/Closeup Photography Part II

Perhaps my last post on macro and close-up photography didn’t convince you to (virtually) run-out and buy a nice new — or even slightly used — macro lens. I get it: they are pricey specialty lenses and you are not going to be #StayAtHome quarantined forever, right? So, how do you explore the fascinating micro world around you without a macro lens? There are in fact several other ways to accomplish this. For this post I am going to explore the fascinating and frustrating use of extension tubes. What’s that, you ask? At a bare minimum it is simply the addition of a hollow section between your lens and your camera body: an extension that happens to be tube! How and why does it work? Basically the further forward from your sensor (or film) that a given lens element is, the closer your lens can focus to your subject. Extension tubes work because they increase the distance between the sensor and a lens. The closer in that one can focus, the more magnification one will capture. Those are the basics though of course there is some nice math behind it. One calculation you might want to remember is that if your extension equals your focal length you have achieved true 1:1 macro resolution.

If you do a search on B&H Photo (okay: I’ve done it for you) you can see that extension tubes range in price from under to $10 a set to more than $100. Why? After all they are just hollow tubes, right? That depends. First, most extension tubes come in sets of 3 (though there are sets of two and some are sold individually) and the usual widths are 12mm, 20mm, and 36mm. They be used solo or combined. But the other thing one should be aware of is that extension tubes come either ‘smart’ or ‘dumb.’ Dumb or manual tubes merely act as extensions and pass NO electronic information to your camera body. Smart tubes pass auto-focusing and usually TTL-exposure data to your camera. They are also more expensive. They also are not made for every make of camera out there and you of course will need to purchase a set — whether manual or electronically-enabled — that has your camera’s mount. I am one of those rare breeds that still shoot with Pentax cameras. It is nice to be in a league of one’s own, but there are limitations…lots in fact. One is specialty gear for the Pentax mount is often as rare as the Blue-Eyed Ground Dove and sometimes even falls into the category of the Dodo. Case in point: several years ago when I first starting exploring macro photography the only extension tubes I could find for the Pentax were non-electronic ones made by Vivitar. I would love to have the TTL exposure control but frankly you will usually have better luck at these extremely close ranges and small depths-of-field foregoing any auto-focusing. I would also suggest that you break out your tripod and cable-release: hand-holding can be bit a bit brutal with tubes. The final recommendation is to experiment with different lenses and different focal lengths. Having said that, extension tubes are considered at their best when used with short to medium focal lengths.

The images below were all captured with an old manual 50mm f1.7 lens shot completley wide-open. They progress from images using the 12mm, the 20mm, the 36mm, and finally using the 12mm and the 36mm combined to give me 48mm, or near 1:1 macro. Click on the first image and view them in slideshow mode and you can also read the technical information about each image. As you view them in order, you can see that as the extension grows the images become in fact more abstract with distortion and incredibly shallow DOFs. I actually consider these technical limitations to be artistic liberations when using tubes versus my straight “real” macro lenses. You might do so as well.


Jeff Clay
Board Chair (but not Chairman of the Bored)

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