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Film - Digital

What is a bellows focusing unit lens?

Another way to allow the lens to focus on a subject to a much closer distance is to use a bellows unit. These are manufactured to fit on 35mm and 120 cameras between the camera body and the lens to extend the focus of the lens for doing close up work. Because these units allow the focus point to be precisely located within their range, - they can be extended out to any length - they give much more flexibility than a series of extension rings which have a set focus distance.

Because the focus is often very critical, when using both an extent ion ring and a bellows unit it can be difficult to locate the subject in the viewfinder, a technique for overcoming this is to move the camera closer and further away from the subject until the objects appears in a recognizable way in the viewfinder. From here you can use the normal focus of the lens to complete the critical focus.


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If we use a standard lens on the camera ( say a 50mm on a 35mm DSLR) with extension tubes or a bellows unit we migh find that the lens is phyically so close to the subject it blocks out the light. By using a longer focal length ( a telephoto say 100mm lens we find to fill the subject in the viewfinder the camera position is now moved back consderably. This allows light to fall uninhibated on the subject. We can also augmet this with a flash light.

Tillandsia plant taken with a standard 50mm lens on maximum focus
Taken with a 100mm lens on a bellows unit
With the bellows unit fully extended
Enlargement of a section of this image



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