Extension tubes are a good low cost alternative for photographers who want to experiment with macro photography without having to buy a lens especially designed for macro. They are a few empty tubes (with no optical elements inside) set between the camera body and your lens, thereby increasing the distance between the lens and the focal plane of the camera (either a sensor or a negative). This fact considerably reduces the minimum focusing distance of our lens and allows us to get much closer to the object to be photographed in macro. In the other hand, when we use optical extension tubes the lens loses the possibility to focus to infinity, so we can only use them to photograph items that are close to us. Another aspect to consider when working in macro photography is the depth of field: it becomes critical and can be only about a few millimeters. Therefore you will usually have to work with closed apertures, that will help you increasing the depth of field to keep a focused scene. In addition, we also have to consider the fact that separate the lens from the camera also causes that less light reaches the sensor, so you have to compensate this fact with ISO or adding more light to the scene. Since the optical principle that use these macro extension tubes is so basic, there are many online tutorials to build them yourself, even starting from toilet paper rolls! But for the same reason we can find some models with good construction quite affordable. Basically there are two types of macro extension tubes: those that have electronic connections and those that don’t. If we chose the electronic ones, our camera will be able to access the information that the lens is transmitting, change the aperture and autofocus. On the other hand, if we use extension tubes that do not have electronic connections we will not be able to modify the lens aperture or auto focus from the camera body, and therefore we’ll need to use manual lenses that allow us to modify these parameters directly on the lens. Extension tubes with no electronic connections can cost about 15€, if you want them with...Read More
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