"Smart Phones" and notebooks/tablet PCs have great cameras that are capable of amazing close-up, macro images just by adding a simple supplementary lens mounted in a plastic holder. The first image in this intro is a photo is regular table salt using the added lens; next to it is an image of the same salt on a magazine cover with a "normal", zoomed camera. The materials and tools needed are readily available if you don't have them already, and it doesn't require a lot of expertise to make the holder.
Step 1: Tools and Materials
table saw or fine toothed hand saw
7/16" or 1/2" brad point drill bit (or whatever size is appropriate for your lens)
drill press with vise or clamps
1/2" hand reamer
3/16" acrylic plastic. This should be at least as thick as your lens so you can get a firm seat to hold the lens. I make my lens holders the same size as my phone, with the lens centered over the camera phone's lens so it's easy to place it in front of the phone when you're going to use it. As far as the color of the plastic, consider that most camera phones and notebook cameras like the Asus Prime that I use have one or more LED flashes right next to the camera lens. If you use clear plastic for the lens holder, your flash can be used as needed. Keep in mind that a flash exposure will often reduce your exposure time, thereby lessening the effect of camera/subject movement causing a blurred image.
lens - 12mm diameter (or larger), 22-25mm (+/- ) focal length, plano-convex lens works well for me. An achromat lens is preferable for better color imaging, but these are apt to be about twice the cost of a plain, single element lens. You can use a slightly larger lens, but you'll need to match the hole that you drill accordingly of course.
Note: I've purchased lots of lenses from Anchor Optics, a division of Edmund Optics. The lenses that I've been using for the camera phone adapters as described above cost about $15 typically. Anchor sells optics for greatly reduced prices, and they have a huge selection of "seconds" and experimental optics. Also, check out their free downloads of some great "How To" documents from the many great experiments in optics from the old Edmund Scientific days at http://www.anchoroptics.com/documents/ . Alternatively, you can also use the "field lens" from a microscope eyepiece - typically, this is the larger of two lenses found in most of them. It's apt to be 20-23 mm in diameter and a focal length of about 22 mm. Just give the lens a try before going to the trouble of mounting it in a holder by holding it in front of the camera and seeing how it works for you.
Step 2: Measure and Cut Acrylic
Cut the piece of acrylic plastic as appropriate. I cut the piece to match the profile of my camera, about 2" X 4". Cutting acrylic plastic can be tricky - you'll want to leave the protective covering on the plastic until you're all through with cutting and drilling it so that it won't get scratched up by handling. The plastic needs to be cut with a very fine toothed blade or it will chip and fracture. You absolutely must use safety glasses! If you don't have a fine toothed saw to do this yourself, or are not used to cutting this stuff, have the plastics vendor cut this for you.
Step 3: Drill and Ream the Hole for the Lens
Drill a hole that is centered where it will match up to the center of your camera's lens. I recommend using a brad point drill for this. This will make it less likely to have the plastic "climb" up the drill bit as it pierces through. You should clamp the plastic onto the drill press or use a vise with soft jaws to make sure that the plastic doesn't get grabbed by the drill bit - this is very dangerous, so be sure that you hold the plastic safely! Wear safety glasses!
With a hand reamer, very gently turn the reamer into the hole. You want to ream from only one side of the plastic so that your opening is very slightly tapered. I have mounted lots of lenses this way, with just a friction fit, but you need to open the hole very gradually to get a good fit. You can see in the included photo that the reamer is just about at the limit of the cutting for this diameter. The lenses that I've been using are exactly 12.5 mm in diameter, and it happens that a 1/2" reamer just makes the correct size. If you have a larger lens, drill out the opening carefully to the right size and, if you want to (you may have to do this...) put a very tiny amount of CA adhesive or a very thin layer of epoxy. This will obviously require a steady hand to avoid getting it on the lens.
Step 4: Place the Lens in the Holder
You want to have the convex side of the lens pointing away from the camera and it's best to push the lens's flat surface till it's flush to the plastic of the lens holder or even very slightly farther, so that you won't have to worry about it getting scratched if you set it down on that side. As I've said, I have had no problems with mounting my lenses as a "friction fit". You will surely want to treat this adapter with care when using it, and hopefully put it into a soft case or or a plastic envelope to protect it, so it shouldn't get bent enough to cause the lens to come out. As mentioned previously, if you want to do so, use a very tiny drop of thin CA adhesive or acrylic adhesive (probably a safer method) and hopefully it will just "wick" into the circumference of the lens.
Step 5: Take Some Pictures!
I have taken some of the images with my Samsung Exhibit phone, which is just about the most basic camera that I've ever used - it doesn't have a zoom (optical nor digital) and the ability to manually focus is pretty limited, but it still takes pretty decent close-up photos. The image of the table salt crystals was made with an ASUS Prime tablet, and it has lots of options for exposure, focus, and zooming. I've also used these lenses with the DROID, and it's capable of taking excellent close-ups. If your camera has a zoom function, try putting it to about 3/4 of the zoom; this seems to work well for close-ups with the supplementary lens. Just experiment with different settings and see what works best for your subjects and lighting conditions. You will find that, when you're very close to your subject, any camera movement is magnified, so you'll want to use the fastest shutter speed that you can.
Step 6: Other Options for Holding the Lens...
You can use a rubber band to hold the plastic lens holder to a phone as is described here. I've also mounted the lens in a small piece of acrylic and then attached some velcro straps (sold as cable ties at office supply and hardware stores) that will wrap around a phone. Another option might be to use velcro directly on the plastic mount to attach it to your phone or notebook....