A digital camera can tell you all you need to know to grow happy, healthy indoor plants.

Let's shed some light on the subject of houseplant growing. For plants to thrive, they need proper sun exposure. To figure out how much you have, you'll need to measure it. Have a digital camera? Great -- if it has an aperture priority setting (many recent models do). How about a large piece of white poster board? Get one at an office-supply store. Then, follow our easy instructions to gauge your room's light. Now you can pick your plants (see our lists of bright-, medium-, and low-light species) and shake that "black thumb" label forever.

Make sure the camera's flash is off (E), and then turn on the aperture priority mode (A). You should see an "A" or "AV" on the camera's screen. Next, set the ISO speed setting (the image sensor's sensitivity to light) to 100 (B). Finally, set the aperture value to 4.0 (C). (Use the diagram, left, as a guide, using the owner's manual if necessary. Manuals are often online.)

Place the white board where your plant will sit. On a table or shelf, prop it vertically (you may need help). On a windowsill, lay it flat (left).

Stand as close as possible to the light source (window) without blocking the light or casting a shadow. If you are reading windowsill light, you may need to stand on a stepladder.

Point the camera at the white board, as if taking a photograph. The board must fill the entire frame without the camera zooming in. Push the shutter button halfway.

The bottom number of the shutter-speed reading (D) approximates the amount of light received in foot candles (fcs). Bright light will register 400 to 800 fcs; medium, 250 to 400 fcs; and low, 50 to 250 fcs.

Record this reading every day for a week, at various times of day. Then calculate the average by adding your readings and dividing by the number of readings you took. You can repeat this process in all seasons for greater accuracy.

Rooms with large, unobstructed windows that let in a generous amount of light during most of the day accommodate a range of flowering and fruiting plants, as well as desert and Mediterranean natives.

If you keep it cool and moist in winter, this plant will earn its keep with pretty, pendulous flowers in saturated colors.

Given little water, bright light, and cool winter temperatures, cacti will respond with stocky growth, as well as showy blooms in spring.

Prized for their unique leaf shapes, ranging from pealike beads to rosettes or waves, succulents store water in their stems, leaves, and roots.

Their stiff leaves make bromeliads striking even after the bright flowers disappear. They tolerate low humidity and dry spells.

This stately, slow-growing conifer has lots of tiny leaves that need even moisture, temperatures above 40 degrees, and good air circulation in order to thrive.

Succulents are a varied group of plants that need little care. If in doubt about watering a succulent, always err on the side of caution and wait a few more days instead. Succulents can tolerate lower light but look their best in full brightness.

The key to success with pomegranates is to simulate their Mediterranean habitat as closely as possible: plenty of bright, direct sun the whole year through, with excellent air circulation and cool (55 degrees) temperatures in the winter. Flowers appear throughout the summer. Never allow soil to dry out completely.

These dry-climate natives tolerate neglect but require plenty of sun to maintain their coloring and tidy shape. The leaves are edged and tipped with spines, so they may not be a good choice in households with pets or children. Water infrequently.

Crotons provide a bold dash of drama and color if used appropriately. They are true tropicals, requiring high humidity, ample water from spring through early fall, and a drier rest during winter.

With lustrous green foliage and sweet goldfishlike flowers, this sprawling plant is nearly irresistible. It requires bright but not direct light and plenty of humidity, and must not be allowed to dry out during the growing season.

Closely related to edible asparagus, this plant isn't a fern at all; rather, it is in the lily family. It requires bright light to maintain its dense columns of foliage but can tolerate short periods of dryness and low humidity. For best growth, water regularly and mist in wintertime.

Myrtle topiaries such as this are very popular, but few homes have the bright light and cool conditions that keep the plants healthy enough to maintain their tight, attractive shapes. They require some direct light and should not be allowed to dry out. Prune growth regularly for the best shape.

Probably the most common exposure, this light results from average-size windows that are not blocked by trees or buildings within 100 feet. It suits most garden-center plants and fosters colorful or variegated foliage.

Lacy, black-green foliage makes this dramatic plant (far left) a standout. The soil should never be allowed to dry out completely.

With its long-lasting red or pink flowers and glossy, heart-shaped foliage, this is an all-season favorite. It likes warm air, ample moisture, and high humidity.

The textured, wafflelike leaves of this small plant (named for its ease of propagation) are irresistible to touch, but avoid wetting them when watering.

Best grown as a hanging plant or in a tall pot to show off its romantically cascading stems, this fuzzy-leaved tropical prefers cool conditions, good air circulation, and ample water.

Calatheas display all kinds of interesting variegation, and most have a hint of tropical pink. Rainforest-floor dwellers, they require consistently moist but not wet soil.

Ivy has a reputation as a difficult houseplant because it prefers cooler conditions than are found in most homes. However, with good air circulation, even moisture, and a site well away from heat sources, it makes an elegant, versatile choice.

Alocasias are better suited to outdoor summertime growing, but they can be successfully overwintered in a bright, but not directly lit, room. Water infrequently in winter; the tuber in the soil will rot readily otherwise during the dormant season.

A wide variety of philodendrons are suited to indoor culture. All are tropical and need ample moisture and high humidity. This handsome vine requires bright light to preserve its silver spots and looks best in a hanging basket or a tall pot.

Most people dislike this plant, not just for its name but also because they have seen only the spindly, sickly looking specimens that have been grown in the wrong location. Sufficient light yields stockier stems and lusher, more attractive foliage. Keep out of cold drafts, and water less during winter.

This sprawling plant with unusual variegation is a bit of an oddball: The red-and-lime markings will actually fade if there is too much light, so medium light is ideal. Do not let the soil dry out, and keep leaves clean with frequent misting or washing.

Spider plants are the ultimate pass-along plant, because of their habit of setting numerous plantlets on long stems. Leave the plantlets in place for a luxuriant, full look. Good light and even moisture will ensure healthy plants.

This is found in rooms where the windows are very small or are shaded by trees (especially evergreens) or buildings. Although few plants thrive in such dim places, some tolerate it. They have rich, green foliage but rarely flower.

These classic houseplants are woody vines from the tropics, and it's best to contain them in small pots. New varieties feature many different kinds of variegation. Although they don't need much light, they do require consistently moist soil.

Don't have a green thumb? This tough customer (center) is almost impossible to kill. It's long been called the barroom plant for its tolerance of darkness and poor air. Water when dry, and dust the leaves. Since it's a perennial in Zones 7 and warmer, you may find it in regular nurseries.

With its need for humidity, this graceful moss relative is the perfect bathroom plant. Keep it moist, watering from the bottom.

The beloved staple of offices and rec rooms. Given just a bit of natural light, the golden and variegated forms will glow.

Sculptural and striking, this plant will survive everything but cold or overwatering.

Many types of dracaena are sold in garden centers, but it is the green variety of the corn plant that best tolerates low light. Dust the leaves to encourage health and vigor, and be sure not to let the soil dry out completely.

These popular houseplants have a reputation for being difficult. They require some natural light, but they also need a great deal of humidity to maintain their graceful profile. Mist frequently, and avoid sodden soil.

Although the plants themselves can tolerate low light, they will be less likely to produce their unusual white flowers in such conditions. The plant should not be allowed to dry out, though it can recover very well from drought stress. If the plant wilts constantly, repot with fresh soil.

A relative newcomer on the houseplant scene, this plant truly thrives on neglect. It is rather slow growing, so start with a plant near the size you'd like. Water when the soil is dry, and wash or dust off leaves occasionally.

This attractive plant grows as a shade perennial in Zones 7 and warmer, so look for it in garden centers. Indoors, it demands cool temperatures and good air circulation, along with moist but not soggy soil.

Popular in Victorian times for its ability to tolerate dark , moody interiors, this plant remains a mainstay. It can withstand occasional drying out and low humidity. Though it tolerates low natural light, it looks its best under brighter conditions.

As with most low-light-tolerant plants, variegated forms will fade or become muddy in very dim environments. To keep this plant looking good, water thoroughly during the growing season and less in winter. Try to provide some humidity, if only through occasional misting.

Find inspiration and practical ideas.

• Shade-Loving Plants
• How to Plant a Tree
• Textured Plants