ISO & WHITE BALANCE 

WHITE BALANCE

Ever wonder why certain film is labeled as daylight film? This designation is used to differentiate between films created for daylight lighting, Tungsten (studio) lighting, or infrared lighting. Film comes with various light ratings because different types of light have different color casts that can affect the quality of your photos. A classic example is the heavy green cast film prints suffer from when pictures are taken under florescent lighting. Just because photography has gone digital, it doesn’t mean that problems from different types of light have been solved. It just means that the digital photographer has more control over these lighting situations than his film counterpart. The easy way to handle various lighting situations is to make sure your camera’s white balance (WB) setting is on auto, and just forget about it. Most digital camera’s auto white balance features do a good enough job of choosing the right setting. Sometimes though, the right setting isn’t the best setting. There’s no rule that says that just because it’s sunny out, your white balance has to be set for sunlight. You can experiment with white balance settings to create different color casts that may be more in tune with the image you want to create. When in doubt, take two pictures: one at the indicated setting and one with the experimental one. Here’s one example. Because heavy shade has a lot of blue light, digital camera white balance settings for shade will add some red to neutralize that blue light. Setting your white balance to shade for a picture taken under direct sun will produce a “warmer” image because of that red.

ISO

Next, consider your choice of ISO settings. ISO (International Organization for Standards) is a measure of how sensitive your film or recording sensor is to light. One of the great advantages of digital cameras is that you can change the ISO settings on the fly. Back in the days when film ruled, if your lighting conditions changed, you had to change your film to match. Digital cameras enable you to change ISO settings to adapt to both changing lighting conditions and also to respond to different shooting situations. Most point-and-shoot digital cameras offer ISO settings of 100, 200, and 400, with each increase doubling the sensor’s sensitivity to light. Many DSLR's offer even more choices and a greater range of sensitivities. Light sensitivity doesn’t come for free. As you change ISO settings to compensate for falling light levels, noise becomes more of an issue. Noise is a problem caused by individual pixels within the camera’s sensor misfiring as their sensitivity is boosted. This problem shows up as individual pixels in the image being the wrong color. Noise becomes most apparent in shadow areas where, instead of a solid black, you find individual red, yellow, and green pixels mixed in with the black ones (see Figure 2-2). Generally, you want to choose the lowest ISO setting that gives you a workable combination of lens opening and shutter speed for the kinds of photos you want to make. Remember, changes in ISO setting affect the overall exposure needed to expose an image properly. Your lens opening and shutter speed are part of that equation, so changing ISO affects those settings too.