$10 Extension Tube Tutorial
By Mike (www.mikeotto.net) with help from Tara (bloodredme.deviantart.com)
The purpose of this tutorial is to show you how to make an extension tube for your film or digital SLR. In case you don’t know, an extension tube is simply a piece that is placed between the lens and body of your camera. What it does is allow you to focus much closer with the same lens than you normally could. I recommend using this with a 50mm prime lens, for two reasons. The addition of space between the lens and body will allow less light to hit the film, and therefore a good fast prime will still allow a useable macro lens. Secondly, we will be adding approximately 50mm of space, giving you a macro lens that goes to about 1:1! “Real” extension tubes cost upwards of $100. What we’re going to build shouldn’t cost much more than a tenth of that. Things you need to know: 1. 2. 3. This is not a macro lens! You will not be able to focus from infinity to 1:1. As soon as you put on the extension tube you will be stuck with a lens that is only able to focus at about two inches from the front of the lens. This is not a real extension tube set. You will not be able to vary the amount of extension. If you want anything less than 1:1, you’re out of luck. IMPORTANT! You need to verify that your camera will meter without a lens mounted. This is simple to test, simply remove the lens and see if your camera produces some sort of useable light reading. Most older cameras do this fine, some newer ones don’t. Some cameras require you to set a certain custom option to allow you to do this, others require you to press some obscure button combination while turning the camera on. See your instruction manual. I know my Minolta Maxxum 4 works if a certain custom option is set right, and Tara’s Minolta XD-11 works great. And lastly, what exactly you will get out of this is rather uncertain. My Maxxum AF tube is rather shoddy since it can easily come off the body, and it doesn’t quite hold the aperture open all the way. Tara’s MD tube is excellent though, it stays on the body perfectly and since she has an aperture ring it’s like bonus DOF preview!
4.
Materials First off you will need a body cap for your camera’s mount. Obviously, it should be opaque and not one of those translucent white ones. It will also need to be one that actually mounts to the body, not just pushed in. You should verify that it stays on fairly well. If it unmounts too easily, like mine, you’ll need to babysit your lens to make sure it doesn’t fall on the dirt beneath the flowers you’re shooting. Secondly, you’ll need a rear lens cap. Again, opaque, and again, make sure it stays mounted solidly. If your lens is one that closes down when unmounted, make sure this cap opens up the aperture, otherwise you’ll have a useless f/22 macro lens. Lastly, you’ll need to venture into your local hardware store for a bit of pipe to act as the spacer. I used a 1.5” ABS pipe coupler, but anything that is about 30mm long and that fits well with your body and lens caps will work fine.
Get on with it! Alright, after a page full of writing we’ll finally get to building the damn thing. First you’ll want to ensure that the surfaces we’ll be putting together are smooth and parallel. Our ABS pipe coupler came with writing on it so we had to smooth it off using what probably isn’t the right tool. I am in no way responsible for any intentional or unintentional amputations that may or may not occur.
Next you’ll want to drill a hole through both the body and lens caps. This is like horseshoes, hand grenades, and shooting architecture: close is good enough. Don’t spend hours obsessing over getting it perfectly centered. You probably don’t have a garage full of tools at your disposal, so you may have to improvise something other than a proper hole saw. Make sure you go good and slow, this is cheap plastic and you probably don’t want to break it.
After that’s done it’s a good idea to smooth out the edge and remove any loose bits of plastic. You really don’t want this stuff getting into your camera body and screwing with your shutter or mirror.
Before gluing the parts together you should try to line them up so that when the whole rig is put together and mounted on the camera, the top of the lens will still be upwards. If your aperture ring is facing the ground all the girls will laugh at you and nobody likes that. Here I use a hot glue gun but you could probably get away with a regular old-fashioned epoxy. No, a glue stick won’t work, but yes, I dare you to try anyway. I like to run a bead inside the part, squish the other piece on top, then run a bead around the outside. Make sure you get your pieces parallel, this is much more important than having them exactly centered. If they are off center slightly you’ll have a slight shift, no big deal, but if they’re not parallel with each other you’ll end up with a tilt and your plane of focus will be all screwed up. After the whole deal is assembled try to tear it apart a bit so that you’re sure it won’t drop your relatively expensive prime lens on the ground. When you’re done you should have something a lot like this. Sexy. If you have any problems or questions email me and I’ll help you out. Hopefully you had fun making this little toy, and have more fun using it on the world of small things around you. Happy shooting! Mike