Up for Discussion – Using Extension Tubes
On this blog I have noticed how many of you seem to enjoy macro photography, me among them. I don’t have a macro lens and it was frustrating me quite a bit, and then Ben, from APERTURE64, suggested I get some extension tubes. He told me how I could use them with my 50mm lens. So I did and they have been fantastic. I also like, now that I have the loan Tamron 90mm Macro lens, I can also use the tubes on it as well. I asked Ben if he would write a post on using them for us.
What is an Extension tube?
Extension tubes are a tube that goes between your camera and lens, at present extension tubes are available for DSLRs with full frame and cropped sensors. An extension is a tube placed between the lens and camera reducing the minimum focus distances of the lens, enabling you to get closer to your subject. As you move closer to the subject the bigger it becomes.
There are many companies that make extension tubes, when buying you really get what you pay for. The more you spend the better the build, which means it is less likely to cause problems with your camera and lens (eg lenses getting stuck or even tubes getting stuck to cameras, it can happen).
There are two types of extension tubes, those with electronic connections, and those without. Electronic connections are important as they allow you to change the aperture of your lens as well as use auto focus. Non-connector tubes won’t let the camera talk to the lens, leaving you unable to change the aperture while the lens is connected to the tube as well as not being able to use the auto focus. The non-connector type will be fine with older lenses with manual focus and aperture ring.
One element of extension tubes that seems illogical is that; the smaller the lens (shorter focal length) the closer you can get to a subject. An 18mm lens will let you get closer than a 100mm lens. Although zoom lenses are great, I tend to use prime lenses as they create sharper images and are lighter. If you attach a heavy lens to a long extension tube, if the lens is not supported this could cause damage to the camera.
How to use
Using an extension tube is just the same as a normal lens. I use Polaroid tubes that came in a set of three; 13mm, 21mm and 31mm. These three tubes can be mixed and matched with each other, with all three connected I have a 65mm extension tube. I add my lens to the tube/s and then attach everything to the camera.
I have found that although I can use auto focus on my lenses it doesn’t really focus and I always manually focus with my lens. The inability to focus is because the AF system doesn’t have enough light to focus with. I manually focus the lens to infinity and move close to the subject until it is sharp. I am usually seen swaying in and out as I take macro shots with my extension tubes, as the area of focus is really slight sometimes a matter of a mm.
Depth of field of the lens is extremely narrow compared to the lens by itself. I prefer to use the sharpest aperture so that the details I capture are sharp instead of having a larger area in focus which is not as sharp. Also as you get closer to a subject the less light there is, using the smallest aperture may not be possible.
I favour the use of a tripod although there are times when that isn’t possible. When using a tripod I use the LCD screen, not the view finder to compose and focus my image, as I can magnify the area I am focusing on to make sure that it is sharp.
Some issues and photo hacks
Extension tubes mean longer exposure times because there is less light reaching the sensor. Without a tripod the rule of thumb for the minimum shutter speed for sharp images is, no slower than the focal length of the lens. Attaching all my tubes and my lens equals an exposure faster than 1/100. As I said early it is not possible to use your tripod all the time, I have found this especially true when photographing insects and bugs. The only way increase shutter speed is to raise the ISO or use a larger aperture. In Raising the ISO you are adding more noise to an image resulting in a lower image quality and using larger aperture would result in a smaller depth of field.
Another option is to use flash. When using flash you want to have even defused light, nothing too harsh as this will create contrast in the image. An expensive option is to buy a ring flash which is attached to the end of your lens. A cheaper photo hack is to use a Pringles tube and some tracing paper.
I call it a flash extender; I eat the Pringles (the fun part) and then cut a square hole on the bottom side of the tub, I then tape tracing paper over the hole. I place this on my flash and securing with tape and then photograph. If it gets battered and damaged eat some more Pringles and start again.
When it comes to photographing insects the major drawback is the lack of auto focus and the need to move in and out to take the shots, this with the need to get quite close to the insects as well has a habit of to making them more skittish. One option is to carry sugar water and place a drop for the insect to feed on giving you some time to take the shot.
Extension tubes are not only for Macro photography they can also be used to dramatically decrease the depth of field, great for portraits and standard still life pictures. Also if used creatively can be great for creating abstract pictures with a large aperture.
Extension tubes are a good cheap alternative to a Macro lens but I will admit once you start to get into Macro photography you will crave to move on from them and buy a macro lens. This doesn’t mean that the tubes are then a waste of money as they can be used with a macro lens to get you even closer.
Thank you Ben, great explanation of what they are and how to use them. I hope you will all thank Ben. He is going to answer comments, so if you have any questions, please ask. If you would like to see more of his work please visit his blog, APERTURE64. I am going to put the images from the post and a couple of others that Ben sent in a gallery for you now.