Optics theory
The net effect of adding an extension tube between a lens and camera body is the “working distance” is decreased, that is, the distance from the front of the lens barrel to the subject is decreased. A smaller working distance means the same lens will focus closer to the subject, thereby increasing magnification.
The effect is greater at shorter focal lengths, as shown by the following annotated table of magnification for the two extension tubes sold by Fujifilm USA.
Table courtesy Fujifilm USA.
Theory into practice
On 27 October 2017 several Autumn Meadowhawk dragonflies (Sympetrum vicinum) were spotted perching on the small dock at Hidden Pond, Meadowood Recreation Area, Fairfax County, Virginia USA. All individuals featured in this photo gallery are male, as indicated by their terminal appendages.
All photos in this set were taken using my Fujifilm X-T1 digital camera, Fujinon XF55-200mm zoom lens, and a Fujifilm MCEX-11 extension tube. The camera was set for manual focus in order to use focus peaking; back-button focusing was used to focus automatically.
At 200mm, the working distance of the lens is 905 mm (90.5 cm, ~35.63 in), or approximately three (3) feet. With an 11mm extension tube mounted between the lens and camera body, the working distance is reduced to 665 mm (66.5 cm, ~26.2 in), or a little more than two (2) feet. At a focal length of 55mm, adding the extension tube would result in photos that look more like “macro” photos; at 200mm, adding the extension tube resulted in photos that look like a lens with a longer focal length was used to take the shots.
All of the following photos were slightly cropped for improved composition. The 11mm extension tube is the difference-maker that enables me to take close-up shots using a mid-range telephoto zoom lens such as the Fujinon 55-200mm.
ISO 640 | 200mm (~300mm, 35mm equivalent) | f/11 | 1/500s | -1 ev
ISO 640 | 200mm (~300mm, 35mm equivalent) | f/11 | 1/500s | -1 ev
When I changed the aperture from f/11 to f/16 (larger to smaller opening) for more depth-of-field, notice the ISO increased from 640 to 800. ISO was set for “Auto” with a limit of 800.
ISO 800 | 200mm (~300mm, 35mm equivalent) | f/16 | 1/500s | 0 ev
ISO 800 | 200mm (~300mm, 35mm equivalent) | f/16 | 1/500s | 0 ev
ISO 800 | 200mm (~300mm, 35mm equivalent) | f/16 | 1/500s | 0 ev
ISO 800 | 200mm (~300mm, 35mm equivalent) | f/16 | 1/500s | 0 ev
More tech tips
Focus peaking can be activated when the camera is set for manual focus mode. Using back-button focus (AF-L button) in manual mode enables one to retain full control of the exposure triangle, focus quickly, and see what’s in focus before shooting a photograph. Fuji Back Button Focus (4:06), a YouTube video by Ashraf Jandali, provides a clear demonstration of how to use back-button focus on the Fujifilm X-T1.
In order to reduce “camera shake,” I almost always shoot in shutter priority mode using the reciprocal rule. Remember, it’s the 35mm equivalent that matters: since my lens is ~300mm, the shutter speed should be set for at least 1/300s; in this case, it was set for 1/500s. In manual mode, I set the shutter speed and aperture; ISO was set for “Auto” with a limit of 800. An inexpensive Sunpak 6700M aluminum monopod was used for added stability.
Editor’s notes
Did you notice I didn’t use an external flash unit to shoot the preceding photos? The afternoon Sun is lower in the sky in late-October than it would be at the same time during mid-summer. I wanted to faithfully capture the shadows cast by the dragonflies in order to convey the feeling that the Sun is setting on these dragonflies, literally for the day as well as figuratively for the current odonate season.
Copyright © 2017 Walter Sanford. All rights reserved.
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