When we want to immortalize the close ups of very small and tiny subjects such as insects, flowers, coins and etc. commonly we need to use macro lens to perform it. This type of photography is called macro photography which is very interesting to be explored since there are so many beautiful yet tiny subjects around us. But this hobby is not cheap because you are required to purchase a macro lens with variety of focal length options. However, there is a cheaper alternative for you who got only limited budget. You may use some camera accessories such as close up lens, reversal lens, and extension tube. For this very opportunity, we would like to discuss about the advantages and disadvantages of using extension tube.
The advantages of extension tube
The name of extension tube itself is based on the use and the benefit of using this item. It is pretty clear that the function of this accessory is to increase the distance between the camera and the lens. The tube creates further forward gap between the lens and the camera. It gets the lens and the subject closer so that the lens is able to focus in a closer distance with the subject so we can get a greater magnification effect. Closer focus and also magnification is the mainstay feature of macro lens which we do not see in any other lenses. Extension tubes lack optical lenses or glass materials inside them, so they will not change the quality of the camera lens we use. Today, extension tube is offered in variety of focal length such as 12 mm, 25 mm, and 36 mm.
For instance, when we would like to attach a 25 mm extension tube to a 50 mm lens, we will increase the magnification effect to 0,5x. Commonly, a 50 mm lens has a magnification ratio of 0, 15x so the effect it gets will count 0, 15+0, 5=0,65x. The magnification ratio result of a 50 mm lens fitted with a 25 mm extension tube is able to come near the ability of a macro lens that usually has a 1x magnification ratio. We can use all 2 or 3 extension tubes in order to achieve the size of magnification we want.
One point which needs to be noted is that the use of extension tube is very effective when it gets fitted with a lens that features a short to medium focal length. However, when it gets fitted with a Tele lens, it will be not at all effective which is interestingly the opposite of a close up lens that works wonders when it get merged with a Tele lens.
The types of extension tube
There are two kinds of extension tube; one that has a connection to the camera and the other which has not. The second type is clearly cheaper because it features a non electrical tube connected to the camera, and we surely cannot control the focus and exposure automatically so we need to do it manually. For some people, this is hardly an issue because most macro images usually use a manual focus to get the best result. One of the weaknesses of this type is the fact that we cannot control the lens aperture. Only when our lens has a manual ring control, we can change the aperture. But if we do not have it, the aperture will remain locked open.
An extension tube with electrical connection is able to control the exposure, auto focus and also the aperture. These two types give us some options. If we like to use it to try and see how it works, then you may use one with non-electrical connection but if you got enough budget it is better to buy one with electrical connection.
Nikon, Canon, and Olympus all produce extension tube while Sony does not. But of course, we still can use a third party item like one from Kenko and Vivitar. To mention specially, there is something odd about one from Pentax brand since the price of its extension aperture is more expensive than the micro lens itself.
The disadvantage of extension tube
There will be some light loss when we use extension tube and it will make the shutter speed get slower and the ISO gets higher. Do not hesitate to increase the ISO to get wider opening of the aperture and narrow depth of field. But it will be a different case altogether if the subject is still. You will need a tripod that will be very useful to drag the shutter speed and lowers the ISO. The best way of using extension tube is to set manual focus.
Macro extension tube by Matt Granger