During this lockdown period, I, like every other landscape photographer, have had to direct my attention to subjects close to hand around the home or garden. You have probably seen from my Facebook page that I have recently taken a few shots of the flowers in my garden, but these are a challenge as I don’t own a macro lens. This week I wanted to do some closer images than are possible normally, so I decided to make a rather crude and rudimentary extension tube for my camera. Extension tubes are used in macro photography to allow the lens to focus at a closer distance than normal. They are a good way to try out macro photography as they are relatively cheap, certainly much cheaper than buying a dedicated macro lens, but they do have some limitations. Compared with a macro lens, the image quality will probably not be as good because a ‘normal’ camera lens is not optimised for close focussing. The lens will also only focus at one point, with the entire camera/lens assembly needing to be moved backwards and forwards to achieve focus, although if used with a zoom lens, the zoom function may allow focussing. The extension tube is essentially just a light-tight spacer that fits between the lens and the camera body - there is no lens inside - but they do usually have the electrical contacts that allow the lens and camera body to communicate about aperture and focus settings, and, of course, the mount to fit the camera body on one end and the lens on the other. They are available in two or three depths to allow a variation in distance between the lens and camera body, thus giving a variation in the magnification factor of the image. If you fit extension tubes that are the same length as the focal length of the lens, then you should be able to achieve a life size (1:1) image on the sensor. This, however, results in the subject needing to be very close to the front of the lens in order to focus, perhaps even touching it, which is not very convenient.
Extension tubes come in various depths to enable different magnification factors
My home-made extension tube is a piece of cardboard tube similar to the centre of a kitchen roll, and has a depth of 10mm. I then taped this to the back of the lens and attached the whole to the front of the camera, again using sticky tape, to make a snug fit, whilst ensuring that the alignment was maintained between the lens and the camera body. Obviously, with no electrical connections between the lens and the camera body, I am unable to change the aperture, which remains wide open on this lens. To get the correct exposure, I am reliant on the selection of the appropriate shutter speed, which can be done manually, but I am letting the camera decide. This is how my camera looks with the home-made extension tube fitted - all a bit difficult to handle, but capable of some good results.
As you can see, this is all bit like a ‘Blue Peter’ project, but effective when used properly
