Starting with a hand lens

As I explained in Embiggening, there is a right way and a wrong way to use a lens. The real Sherlock Holmes would have known this, but the actors who played him don’t. For the best results, you need to hold the lens close to your eye, and move the object towards you until you see it in clear focus. With the lens near your eye, you will find there is a small flat zone where everything is in focus.

Photographers call this area the focal plane. It is flat and lies at the exact distance of best focus. Anything above or below this level will be out of focus and blurred. When you hold the lens close to your eye, the things you are looking at appear less distorted if they are in the focal plane. Note that this applies in all aspects of looking at small things.

Any hand lens will help, but the best sort is the two-lens variety, lower left in the pictures above (and also on the right). In that right-hand picture, look at the size of the image where the lenses overlap. Each lens magnifies, and together, they give around x20 (meaning a magnification of 20 times).

For field work, you need a folding hand lens, or jeweller’s loupe. You can buy these at natural history shops, camera shops and telescope shops. A web search on <jeweller loupe site:.au> will find people selling reliable loupes from about $10 or $15 upwards.

For about $30, you can get a lens advertised as x30 and x60: I have one of those, and it seems good, but you don’t quite get the claimed magnification. You never do, with cheaper optical gadgets.
 

The main benefit from these new lenses is the light. The shots on the right were taken with a similar power clip-on. Here, you see a thumb print and a hairy leaf, taken with a clip-on.

Get to know your hand lens before you start examining living things. Look at your fingertips, cloth, wood, newspaper, stones, leaves and anything else that is in reach. Then look at some leaves and flowers, any insects you can find, and some soil. Once you have mastered the hand lens, why not examine some sand, close up? Microscopes are usually better, but we will get to them later. I will deal with sand next.

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