This is how to make a cheap macro lens for a camera which does not have a built-in macro feature. The one I am showing here is designed around a housing for my cheap underwater camera, but you can easily re-design this to fit whatever camera you'd like.
For those of you who don't know, the purpose of a macro lens is to allow your camera to take closeup photo's. Most cheap point-and-shoot cameras only let you get to within 1m or so of your subject. With the addition of a macro lens you can get much closer. A 2-3x magnifying lens will allow you to get within 10-15cm.
This project is quick, simple, can be put together for a few bucks, and only takes an hour to do!
I've made similar lenses to fit onto underwater video housings and an SLR housing. They all work fairly well. Unfortunately, I only took pics of the first, simplest lens I made. For you underwater SLR junkies out there, if you're using a flat port this is a way of getting a limited macro ability with a normal/wide-field lens. Unfortunately, it is not cross-compatible with dome ports.
A few note on lenses:
1) The lens you pick will have a huge effect on your final results. Generally speaking you want a 2x-4x lens; any less and you won't get enough magnification; any more and your working distance will be too short to be useful.
2) Glass is better than plastic, especially for underwater use. Glass is more durable, and less prone to scratching. Under water, both types of lenses will loose magnification (because the refractive index of water is not the same as in air), but the effect will be less for a glass lens.
Step 1: What You Need.
1. 2x to 4x magnifying lens. Glass is better than plastic. Lenses are not to hard to find - I "borrowed" mine from a dead microscope at work, but you can get yours from coin/stamp collecting shops (good lenses quality lenses are used for their inspection lenses - loupes I think they're called). Some hobby/science stores may sell loose lenses.
2. Sheet of thermoset plastic, 1/16 to 1/8 inch thickness. This should be available from most hobby stores.
3. Bottle, tube, or some other container the same approximate diameter as
the lens port on your housing (this is used as a mold). You need to boil this, so don't use your camera ;-)
4. Cyanoacrylate (instant/crazy) glue
5. Silicone glue
6. Short piece of cord (optional)
Step 2: Making the Retaining Ring
Cut a piece of thermoset plastic 1.5-2x as wide as the housing port is deep, and 4-5x longer then the circumference of the lens port.
Step 3: Set the Curvature If the Retaining Ring
Wrap plastic around the mold, securing in place with duct tape. Dip the mold into boiling water for 20-30 seconds, this will set the plastic into a coil with the same diameter as the mold.
I've found if I just bend the plastic, and don't use thermosetting, that the lens tends to burst apart after a few days.
Step 4: Cut the Retaining Ring
Once cooled remove the coil from the mold. Cut 1 complete spiral, plus a bit extra, from the coil.
Step 5: Make the Retaining Ring
Fit the coil around the lens port. Trim it such that it is exactly the right diameter, and will tightly grip the lens port when glued shut.
Now, peel off the protective plastic coating and remove the ring from your camera. Use instant glue to temporarily hold the two ends together. When dry, test the fit. This bond isn't too strong, so if the ring fits the camera too loosely you can just break this seal, trim, and re-glue.
Step 6: Mount the Lens
So I forgot to take a few pictures here, so here's the rest of it without much ado:
First, reinforce the joint by cutting a short (2cm) long pieces off of the coil you made in step 3. Glue this piece on the outside of the joint with instant glue.
Next, press-fit the collar onto the camera and inert the lens. Tack the lens in place with instant glue, and remove the collar.
Seal the lens firmly in place with silicone glue, or some other type of flexible glue. Instant glue doesn't bond glass well, and lacks flexibility, so it isn't sufficient to hold the lens in place. I had my first few lenses pop out an inopportune times until I began using a flexible glue.
Let the whole thing dry, and you're ready to go.
Step 7: Take Pictures
The lens is now done! Simply pop it on an start shooting your close-ups.
1) Most cheap cameras are fixed focal-length cameras, meaning that they lack the ability to focus. If your camera is one of these then you'll have a fairly narrow range where your subject will be in focus. With practice this isn't too hard to deal with, but it can be frustrating. Practice is about the only way to get around this.
2) The focal length will be different underwater, so if you're doing this for an underwater camera you'll need to practice under water to get the focal length right.