It may be strange to think of light as a tool because it always seems to be there. After all, you can take a snapshot almost anywhere with either available light or the illumination from a built-in flash which turns on automatically. In fact, you are always choosing your lighting (even if only by default), and it is shaping how your subject appears.
The key to effective product photography is lighting, and the key to effective lighting is control. Once you understand how, you can control the strength, size, position, color and number of lights you use. And each of these controls changes how the subject looks.
However, let's take it one light at a time...
An Easy and Simple Window Lighting Photo Setup
If I had to choose just one light to use for product photography, it would be the illumination coming from a bright, non-sunny window. That's because this light is both large (which is what makes it diffuse and soft), and it is directional which can help show off the shape and texture of my subject.
Here is probably one of the most basic eBay photo setups, right next to a bright window. In this setup, a sheet of white posterboard is clamped to a small table, curved up and clamped again to the back of a chair.
Use a Tripod for Sharp Photos
Notice that my camera is on a tripod. A solid support for your camera is another important tool because it will avoid subject blur due to camera motion. Most "out of focus" shots aren't really that at all. They look blurry because the camera moved a tiny bit during the exposure.
Notice also that while the window throws a nice soft glow on the little bronze rabbit I'm shooting, the left side of the rabbit is pretty dark...
Creating a Second Light with a Photographic Reflector
So, I'm going to add a second light to lighten or fill the shadows on the other side of the subject. In this case, my fill light is nothing more than a flat piece of posterboard, propped up and used as a reflector. For those who like to know the "in" jargon, such a flat reflector is commonly referred to as a "flat."
This concept of a main light (sometimes called the "key light" more jargon) and a fill light is important because it's a way for you to control the highlight and shadow values in your scene. Thinking of the reflector shown above as a fill light, I could have increased or decreased its strength by moving it closer to or farther away from the subject. Or, I could have made it much brighter by covering it with aluminum foil.
If the main light is too strong in relation to the fill light, the highlights will be washed out and the shadows will be too dark. If the fill light is too strong, you might wipe out the shadows completely and lose the sense of shape they give your subject.
One of the advantages of a digital camera is seeing an immediate review of your results on the LCD screen, so you can easily experiment with your fill light until the ratio of highlights and shadows looks right to you.
So, here's our little rabbit, shot with the above setup...
Basic Artificial Light Photographic Setup
But what if you don't have a handy window like that or need to shoot at night?
Then, you can use plain old tungsten (incandescent) light. These are just regular household bulbs the kind you use in your table lamps. A couple of 150 watt bulbs would be enough as long as you remember to use that tripod.
You can use these bulbs in either photographic reflectors with light stands (available on eBay or from a camera shop) or just in simple clamp-on reflectors (sold at home centers for $10 or less) such as this one...
Here, thanks again to shipscript, is a simple indoor two-light setup...
Notice both lights are at about 45-degree angles to the subject and the fill light is farther back so it won't be as strong. In general, if the wattage of the two lights is the same, you want the fill light to be about 50% farther away. Or you can use a lower wattage bulb in your fill light and position it at about the same distance as your key light.
Photographic Light Diffusing for Window-Like Softness
You can turn those lights into soft, window-like sources by aiming them through translucent white material (a sheet of tracing paper, a piece of white plastic, etc.) or by bouncing them off reflectors.
Professional photographers use many tools and techniques to diffuse light. If you don't mind spending a few bucks (or more), here are a couple of the more useful ones.
Using a Photographic Umbrella as a Diffuser
First, below is a white photographic umbrella attached to a studio light. In this case, the light is shining through the umbrella, but the whole thing could also be turned around to use the light bounced off the inside surface of that umbrella...
A Softbox Diffuser
Below is another professional lighting tool, a softbox (not to be confused with a light tent more about that later).
A softbox is a large cloth reflector. The light is placed at the rear of this reflector and shines through a large translucent front panel. It's almost like having a large window but one you can place and aim wherever you want. Here is one aimed horizontally...
And in this case, it is aimed straight down over my eBay shooting table...
Accent Photo Lighting for Effect
In addition to key (main) lights and fill lights, photographers often add accent lights for special effects. For instance, in portrait photography, a photographer will sometimes use a "hair light" to add highlights on the subject's hair. This can also help separate the subject from a dark background. This small light is placed high, on the back side of the subject (often somewhat to the side, to keep it out of the picture).
However, you don't have to buy or use lots of lights when you're dealing with small items for eBay. For instance, a simple magnifying makeup or shaving mirror can reflect your main light in a small controlled spot back at the subject. I use one whenever I want to add some sparkle to an item. Here is one being used to brighten up that little rabbit, along with a single softbox...
You might notice I also used a long piece of black posterboard to create a graduated shadow on the background. Here's the resulting shot...
Check out Jewelry where I take up the subject of how to shoot jewelry and other shiny items using a light tent.