Extension tubes on the Hasselblad
Published on 13 June 2017
Extension tubes are a very easy and extremely flexible way to add close-up and macro capabilities to a camera. They are also considerably less expensive than dedicated macro lenses. Extension tubes increase the magnification by moving the lens further away from the focal (film or sensor) plane. It is this 'extension' of the lens which increases the magnification; the tubes are just light-tight cylinders without optical elements.
Lens magnification increases by the extension divided by the focal length. As a result, they are most useful with shorter focal lengths. For instance, on the photo at left the Hasselblad 32E (32mm) extension tube has been attached to the Carl Zeiss 50mm Distagon C T* resulting in a magnification increase of 32/50=0,64x. Adding also the 16E tube to this lens will result in nearly 1:1 magnification (0.96x to be exact).
Benefits and disadvantages
There are a few aspects to the use of extension tubes which may, depending on the particular photographic application in question, be beneficial or disadvantageous.
First off, extension tubes exist with and without electric contacts. The former are normally brand-specific and therefore more expensive. The benefit is that they will retain metering and autofocus. That said, for macro photography manual focus is often useful for full control and metering can often be done manually or by activating the camera's meter separately from the focusing system. Extension tubes without electric contacts can therefore be a very inexpensive way to explore macro photography.
The use of extension tubes will affect the minimum and maximum focusing distance of the lens. For macro photography this is obviously good because one is able to get close to the subject. By using tubes to obtain a high magnification with a short focal length it is possible to fill the frame with a subject or details of a subject. But reduction of the minimum focusing distance is not only useful for macro applications; it can also be beneficial with longer lenses for portrait photography. For instance, a shorter tube on may permit a tight headshot whereas without it one would only have been able to shoot a portrait with the shoulders visible. To put this in perspective, consider this information (distances counted from the front of the lens):
|50 Distagon C T*||w/o tubes||16E||32E||16E+32E|
|80 Planar FE||w/o tubes||16E||32E||16E+32E|
|350 Tele-Tessar FE||w/o tubes||16E||32E||16E+32E|
See how the distances shrink dramatically with the shorter focal lengths, and how very narrow the working distance (min. to max.) is with the 50 Distagon C T*. Conversely, by using the 16E tube with the 350 Tele-Tessar FE, it is possible to move quite close to a subject and fill the frame with the subject's face. For macro purposes, an 80mm lens in medium format is in some way a "sweet spot" lens because it retains a useful working distance also at higher magnification, such as with the 16E and 32E tubes combined. This magnification is enough to get close without getting too close. Here is an example where both tubes were used with the 80 Planar FE.
Extension tubes will reduce the depth-of-field, and often by quite a bit. This means that in practice one needs to use a much smaller aperture (higher f/stop) than what one might think is necessary to get sufficient depth-of-field. Below is a shot where I used the 16mm extension tube with the Carl Zeiss 80 Planar FE at f/11. The distance was 25cm. This is an old 1990s harddrive that is approximately 10x14x2cm. Focus was on the arm, but even at this fairly small aperture the barcode is slighly out of focus. There is a 2000dpi scan on Flickr.
An extension tube will also affect exposure, though in my experience and for most of my photography the effect is negligible. When I shoot macro outdoors there is usually plenty of light around so I never adjust exposure. Film is also so forgiving that in most cases the small changes in exposure will have little real impact on the result and can easily be countered in post. But it is important to be aware of the light loss, particularly with longer extension and in view of the fact that one will normally also need to use a much smaller f/stop to obtain sufficient depth-of-field. For some applications, such as indoor macro photography where one must control the light oneself, it may be necessary to calculate exposure quite carefully. For reference there is a Hasselblad Close-Up Photography document which describes the technical side of using extension tubes, including adjustments to exposure.
I use extension tubes a lot for outdoors macro work and often shoot handheld because I like the simplicity of light camera gear. But while the light is normally enough for sufficiently fast shutter speeds and sharp photos with short focal lengths, the narrow depth-of-field may make accurate focus a challenge when shooting handheld. It pays off to have a stable shooting position or use tripod.
Extension tubes with the Hasselblad V system
For the Hasselblad V system there are tubes without electronic contacts which were made for the 500 series cameras and tubes with contacts made for the electronic 200/2000 series cameras.
All non-electronic extension tubes can be used on all Hasselblad V series reflex cameras made since 1957, including the electronic cameras. There are two shorter tubes, 8mm and 10mm, which cannot be mounted directly on these cameras due to the protruding shutter speed ring, but they can be used in combination with an electronic tube. This obviously breaks the electronic connection and one therefore needs to stop down the lens and meter manually.
The electronic extension tubes can be mounted on all V series cameras, whether electronic or not. As can be seen above, they also work with non-electric lenses, but one needs to stop down the lens to meter manually.
When attaching and removing extension tubes it is important to follow the right protocol to prevent the lens from jamming. The rules are:
1) never attach a tube directly to a lens, or
2) never remove a lens with a tube attached.
This is the step-by-step procedure: One first attaches the extension tube to the camera. Then any second or more tubes in turn. Only with the tube(s) attached can one attach the lens. To remove extension tubes one does the same but in reverse order, that is, start by removing the lens, then the tubes one at a time. As always lenses and the camera body must be cocked. It sounds complicated but it is very easy in practice. Hasselblad Historical has a copy of the instruction manual for electric tubes.