 Jack F. Swallow |
Taking Close-ups I have Pentax 645 and a Heliciod tube. Is there anyone who ca help?
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Jon Close |
Yes. http://www.pentaximaging.com/files/manual/645_Helicoid_Extension_Tube.pdf
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Jack F. Swallow |
thanxs, I have that document. I was hopping for some hands on.
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Michael H. Cothran |
I'm not sure exactly what your question is with the helicoid tube on your Pentax 645. I can offer some generic info, and if it's not what you're after, perhaps you can re-respond with a more specific inquiry. Close-up photography is achieved by lengthening the distance between the camera (ie, film plane) and the lens. The farther the lens is from the film plane, the "closer" you can focus. This is the purpose of an extension tube - to "extend" the lens farther from the camera body than it would normally be able to go by itself. The term "Helicoid" refers to the common focusing mechanism found in modern lenses. It is a threaded device, that when turned (by the focusing ring), causes the lens to move forward or backwards in order to focus. Extension tubes are usually "fixed" in length, and cannot be extended any farther than the tube size that it is cut. Normally, you can buy extension tubes from a manufacturer in at least three different lengths, and all can be combined in any order to achieve different length tubes. The longer the extension tube, the closer it will allow you to focus with any given lens, as it is "extending" the lens farther and farther away from the film plane. A helicoid extension tube is an extension tube which has the advantage and luxury of helicoid threads built inside, just like your lens, which enables you to "vary" the length of the tube, yielding variable close-up distances. As a final analogy, consider this - Hope this helps somewhat.
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