Torwag started a thread in the forum with lots of interesting tips for taking macro pictures of PCBs without buying an expensive macro lens:
Many here know how difficult it could be to do good detailed images of your project. A lot of point and shoot cameras are not up to this (macro) task. DSLRs might work nice, however, you have to cash out a big chunk of money to get a decent macro lens. The reverse lens trick is well known among photographers.
Basically you mount an ordinary lens with the help of a reverse ring adapter upside down on the camera body. This turns a small focal length lens into a super-macro lens.
Take a magnifying eye loupe and hold it in front of the lens, that works pretty good too. If you have a small digital camera, often the eye loupe can be held over the lens with some rubber tack.
Yes, for true macro photography (sensor image larger than physical device) a reversal ring works better than an extension tube. The lens will have better optical performance in this configuration. Whether this makes up for the possibly reduced lens functions depends on your situation. If you are doing 1:1 imaging or less, then stick with extension tubes.
For the best performance in macro work, leave your normal lens on, and screw a reversed lens on the front of it. The reversed lens can have its aperture wide open and have its focus set to infinity, and should be shorter focal length than the primary lens. You will need a good camera mount to hold this stable.
So is a lens reversing adapter that much better than a set of extension tubes (which are also cheap, and probably preserve more lens functions)?
Extension tubes are probably better, especially the ones that forward the electronics connections to the lens. YOu can also use close up Filters (probably the cheapest option, but the easiest to use…you cna get a ste of 3-4 different magnifications, They however add distorsions around the corrners, so high f-stop values are recomended, this requres more light/longer exposures, so a tripod is also needed (this is commonn to most macro photography, so I don;t see it as a negative)
Yep, reversed lenses work great. I did most of these shots with a reversed $35 lens I bought on eBay and an $8 reversed lens macro adapter ring on my bridge camera (non-removable lens):
http://diephotos.blogspot.com/
Or just stick the PCB in your flatbed scanner. As long as the components aren’t too high the results will be really sharp without too much distortion.