Pixiq

Incandescent Continuous Lighting

Continuous lighting may have a longer association with portrait photography than flash, but for most professional photographers it is no longer their first choice. The main reason for this is because flash is more versatile. Unlike a flash unit, a photographer has very little control over continuous lights such as incandescent lamps, as the power is largely determined by the strength of the bulb and the lamp’s distance from the subject. The warm tungsten glow is also a far cry from the color temperature of daylight, meaning the lights have to be filtered if you want to use them in daylight and match the color temperatures of both light sources.

However, perhaps the least desirable trait of incandescent lighting is the amount of heat they generate—it isn’t for nothing that these lamps are often referred to as “hot lights.” Because incandescent lamps work by heating a tungsten filament to produce light, they naturally create a large amount of heat, which can become particularly unpleasant for all involved if several lamps are used at once in a fairly small studio.

It isn’t just the photographer and their model that suffer from the heat; the accessories fitted to the lights will suffer too. Because of the high temperature generated by even a relatively “weak” 800-watt bulb, incandescent lights require specialist heat-resistant softboxes, which cost more than their flash counterparts. Any sort of reflector dish that might stifle the flow of air—such as a snoot—is also not a good idea as it can cause the lamp to overheat, and possibly explode.

Having said all that, incandescent lights do have one major advantage over flash—what you see is what you get. Unlike flash lighting, which generally requires trial exposures to see how the lighting looks, when you’re using a continuous light source, the effect of any light can be seen “live” on the subject and, if it isn’t falling where you want it to, it’s easy to identify and fix the problem. Because of this, continuous lights are great for those starting out in portrait photography who don’t have an in-depth knowledge of flash. The low purchase price of incandescent photo lights also means you don’t have to commit yourself to spending a lot of money if you simply want to give it a go.

Color Temperature

Unlike the other lights shown here, incandescent lighting has a much warmer color temperature than daylight—3200K (degrees Kelvin) compared to the 5500–5600K of daylight. This is more of an issue with film-based photography than it is with digital, as you can simply set your camera's white balance to incandescent, but you'll still need to use blue gels over the lights if you want to match their color temperature to daylight.

Incandescent Safety Tips

To avoid any hot light disasters, observe the following:

• Take regular breaks and switch off the lights to allow them to cool.

• Never leave incandescent lamps unattended when they’re switched on.

• Use dichroic filters to convert the tungsten light to daylight, rather than acetate gels— dichroic filters will better withstand the high temperatures.

• Never try to make your own lighting accessories. A card snoot may work on a flash, but on a hot light it’s a potential fire hazard.

• Only use accessories designed specifically for incandescent lighting. The softboxes might cost more, but that’s because they’re heat resistant.

Pros/Cons

+ Very easy to use—what you see is what you get.

+ Low cost.

– Produce a lot of heat. 

– Need to use gels to balance them with daylight.

– Limited range of accessories.

HMI Continuous Lighting

An abbreviation of Hydrargyrum Medium-arc Iodide, HMI lighting became a popular alternative to flash in digital photography’s infancy, especially with high-end advertising and fashion photographers. The problem for pioneering photographers using digital backs on their medium- or large-format cameras was that the early digital backs “scanned” an image, rather than making a momentary, split-second exposure. This meant a continuous light source was needed, and the answer was HMI lighting—a technology already established in movie and television production.

One of the main reasons HMI works so well for photographic work is that it operates at a color temperature of 5600K, so it mixes readily with daylight. In addition, HMI lights use an arc lamp that consumes far less power than an incandescent lamp and runs at a much cooler temperature—an important consideration when multiple lights are needed in the confines of a studio.

However, while HMIs are still used widely in the movie and television industries, their use in stills photography has declined. Today, cheaper continuous lighting alternatives have been developed, and the “scanning” digital camera backs that once made continuous lighting a necessity have largely been updated, at least when it comes to portrait photography.

Pros/Cons

+ Cool running.

+ Daylight balanced.

+ Generally exceptional build quality.

– VERY expensive.

– Lack of accessories for stills photography.

– Require a bulky "ballast" pack to ignite and regulate the electrical arc.

Fluorescent Continuous Lighting

Fluorescent studio lighting is a relatively recent addition to the continuous lighting options available to photographers, and it largely falls into two distinct groups: high-end, professional fluorescent lighting equipment (from manufacturers such as Kino Flo and Balcar) and “prosumer” lights that are becoming ever more prevalent in photo stores and on Internet auction sites. It’s the latter that we’ll focus on here as the typically low purchase price potentially makes them the most appealing option for portrait photography.

Many of the prosumer fluorescent lighting kits you’ll see use a variation of a screw-fit, “daylight balanced” fluorescent bulb, with numerous bulbs housed in a single lamp to increase the brightness of the light. Regardless of the number of bulbs used, the temperature of the lights remains cool when they’re turned on, especially compared to incandescent lamps. However, with a nominal color temperature of around 5000K, many of these lights aren’t quite a true match for the accepted temperature of daylight (5500–5600K). Although they aren’t far off (and the disparity can be overcome with a custom white balance setting on your camera), if you wanted to mix them with daylight or flash, the difference would show.

It’s also worth considering what accessories are available for the lights. As we’ll see on pages 22–25, accessories that modify the light will give you greater versatility in what you can achieve in your portrait photography, but only a few manufacturers produce lighting accessories for their fluorescent lamps. Unless you’re careful, you could easily find yourself with a couple of low-cost lights that restrict your creativity...

Pros/Cons

+ Cool running.

+ Low cost.

– Not necessarily daylight balanced.

– Limited accessories.

– Some models suffer from poor build quality.

Above: Most low-cost fluorescent lights use a screw-fit bulb that has a nominal color temperature that matches daylight.