Magic Lantern Guides®: Canon EOS Rebel XSi EOS 450D

Digital Photography:

The Revolution Continues

Canon started the affordable digital SLR revolution when the original EOS Digital Rebel was introduced in 2003. For the first time, photographers could buy a digital SLR (D-SLR) for under $1,000 US. In 2005, Canon introduced the EOS Digital Rebel XT, improving on almost every aspect of the original Digital Rebel. Then in 2006, Canon presented the third generation, the Canon EOS Digital Rebel XTi. Continuing the revolution is the Canon EOS Rebel XSi, also known as the EOS 450D outside North America. With its introduction, Canon has continued to set the standard for affordable digital SLRs.

Introduced in January of 2008, the Canon Digital Rebel XSi’s body measures only 5.1 × 3.8 × 2.4 inches (128.8 × 97.5 × 61.9 mm) and weighs just 16.8 ounces (475 g) without lens. Yet the Rebel XSi offers a newly developed 12.2 megapixel image sensor, along with additional features that compare favorably with cameras that come with a much higher price tag. The Rebel XSi does far more than simply replace the Digital Rebel XTi—it has improved many features, and includes new technology like Live View shooting, 14-bit analog-to-digital conversion, and Auto Lighting optimization.

The EOS Rebel XSi is sold in both black and silver versions.

Some photographers have purchased the Digital Rebel XSi as an upgrade from the Canon EOS Digital Rebel, Rebel XT, or Rebel XTi. Others, however, are making their first high-quality digital camera investment. For those photographers new to digital SLR photography, this book begins with an assortment of basic topics and concepts. Experienced digital photographers and anyone already familiar with these terms and concepts should skip ahead to the detailed sections on camera operation, beginning on page 27.

As a matter of convenience (and easier reading), I usually refer to the Canon EOS Rebel XSi simply as the Rebel XSi or the XSi. As previously mentioned, outside of North America the same camera is known as the Canon EOS 450D.

Canon created the multi-featured Rebel XSi so it would meet the requirements of photographers of all levels of experience. While this book thoroughly explores all of the Rebel XSi’s features, you certainly don’t need to know how to operate every one of them. Once you understand what a feature does, you may decide it is not necessary to master it in order to achieve your desired photographic results. Learn the basic controls. Explore any additional features that work for you. Forget the rest. At some point in the future you can always delve further into this book and work to develop your Rebel XSi techniques and skills. Just remember that the best time to learn about a feature is before you need it.

Digital cameras do some things differently than traditional film cameras, making them exciting and fun to use, no matter whether you are an amateur or a pro. For digital beginners, many of these differences may seem complicated or confusing. Though most of the features found on a traditional Canon EOS film camera are also available on the Rebel XSi, there are many new controls and operations unique to digital. Other features have been added to increase the camera’s versatility for different shooting styles and requirements. The goal of this guide is to help you understand how the camera operates so that you can choose the techniques that work best for you and your style of photography.

Differences between

Digital and Film Photography

Just a few years ago it was easy to tell the difference between photos taken with a digital camera and those shot with a traditional film camera: Pictures from digital cameras didn’t measure up in quality. This is no longer true. With the Rebel XSi, you can make prints of at least 16 × 20 inches (40.6 × 50.8 cm) that will match an enlargement from 35mm film.

Although there are differences between film and digital image capture, there are many similarities as well. A camera is basically a box that holds a lens that focuses light onto a light sensitive frame, or medium. In traditional photography, the light sensitive frame is a piece of film that is later developed with chemicals. In digital photography, however, the light sensitive frame is the image sensor that converts the light to voltages. The camera then converts the voltages into digital data that represent the pixels that make up an image. In essence, unlike a film camera, a digital camera develops the image within the camera.

Film vs. the Sensor

Both film and digital cameras expose pictures using virtually identical methods. The light metering systems are based on the same technologies. The sensitivity standards for both film and sensors are similar, and the shutter and aperture mechanisms are basically the same. These similarities exist because both film and digital cameras share the same function: To deliver the amount of light required by the sensitized medium to create a picture you will like.

However, image sensors react to light differently than film does. From dark areas (such as navy blue blazers, asphalt, and shadows) to midtones (blue sky and green grass) to bright areas (such as white houses and snowy slopes), a digital sensor responds to the full range of light equally, or linearly. Film, however, responds linearly only to midtones. Therefore, film blends tones very well in highlight areas, whereas digital sensors often cut out at the brightest tones. Digital typically responds to highlights in the way that slide film does, and to shadows as does print film.

The LCD Monitor

One of the major limitations of film is that you really don’t know if your picture is a success until the film is developed. You have to wait to find out if the exposure was correct or if something happened to spoil the results (such as the blurring of a moving subject or stray reflections from flash). The Rebel XSi features a large LCD monitor (3 inches; 7.62 cm) so you can review your image within seconds of taking the shot. Though you may not be able to see all the minute details on this small screen, the display provides a general idea of what has been recorded, so you can evaluate your pictures as soon as you shoot them.

The LCD monitor is a valuable tool in digital photography, allowing you not only to review photos, but also to see all types of information about the settings and images, including the shutter speed, aperture, metering mode, and histograms.

The Histogram

Whether you shoot film or digital, the wrong exposure causes problems. Digital cameras do not offer any magic that lets you beat the laws of physics: Too little light makes dark images; too much makes overly bright images.

With traditional film, many photographers regularly bracket exposures (shoot the same image several times while changing settings, e.g. increasing or decreasing shutter speed or aperture on consecutive shots) in order to ensure they get the exposure they want. You can still bracket with digital if you want—the XSi can do it automatically for you—but there is less of a need because you can check your exposure as you shoot.

A histogram that stretches from left (dark tones) to right (light tones) and slopes to end at each axis will contain a full range of tones without clipping either shadows or highlights. © Kevin Kopp

The Rebel XSi’s histogram function helps in this evaluation. This feature, which is unique to digital photography, displays a graph that allows you to immediately determine the range of brightness levels within the image you have captured (see page 129).

Film vs. Memory Cards

Images captured by a digital camera are stored on memory cards. These removable cards affect photographic technique by offering the following advantages over film:

More Photos: Standard 35mm film comes in two sizes: 24 and 36 exposures. Memory cards come in a range of capacities, and all but the smallest are capable of holding more exposures than film (depending on the selected file type).

Reusable: Once you make an exposure with film, you have to develop and store the negative and print. Due to a chemical reaction, the emulsion layer is permanently changed, so the film cannot be reused. With a memory card, you can remove images at any time, opening space for additional photos. This simplifies the process of organizing your final set of images. Once images are transferred to your computer (or another storage medium—burning a CD is recommended), the card can be reused.

Durability: Memory cards are much more durable than film. They can be removed from the camera at any time (as long as the camera is turned off) without the risk of ruined pictures. They can even be taken through the carry-on inspection machines at the airport without suffering damage.

No ISO Limitations: Digital cameras can be set to record at different light sensitivities or ISO speeds at any time. This means the card is able to capture images using different ISO settings, even on a picture-by-picture basis. With film, you must expose the entire roll before you can change sensitivity.

Small Size: In the space taken up by just a couple rolls of film, you can store or carry multiple memory cards that will hold hundreds of images.

Greater Image Permanence: The latent image on exposed, but undeveloped, film is susceptible to degradation due to conditions such as heat and humidity. With new security precautions at airports, the potential for film damage has increased. But digital photography allows greater peace of mind. Not only are memory cards durable, their images can also be easily downloaded to storage devices or laptops. This flexibility comes with a risk—the chance that images may be inadvertently erased—so make sure you make backups.

ISO

ISO is an international standard method for quantifying film’s sensitivity to light. Once an ISO number is assigned to a film, you can count on its having a standard sensitivity, or speed, regardless of the manufacturer. Low numbers, such as 50 or 100, represent a relatively low sensitivity, and films with these speeds are called slow films. Films with high numbers, such as 400 or above, are more sensitive and are referred to as fast. ISO numbers are mathematically proportional to the sensitivity to light. As you double or halve the ISO number, you double or halve the film’s sensitivity to light (i.e. 800 speed film is twice as sensitive to light as 400 speed, and it is half as sensitive to light as 1600 speed).

I can photograph my old dog Bucko indoors in low light using ISO 800, and then immediately lower ISO to 100 when I follow him outside to get some shots as he plays in the backyard.

Technically, digital cameras do not have a true ISO. The sensor has a specific sensitivity to light. Its associated circuits change its relative sensitivity by amplifying the signal from the chip. For practical purposes, however, the ISO setting on a digital camera corresponds to film. If you set a digital camera to ISO 400, you can expect a response to light that is similar to ISO 400 film.

Unlike film, changing ISO picture-by-picture is easy with a digital camera. By merely changing the ISO setting, you use the sensor’s electronics to change its sensitivity. It’s like changing film at the touch of a button. This capability provides many advantages. For example, you could be indoors using an ISO setting of 800 so you don’t need flash, and then you can follow your subject outside into the blazing sun and change to ISO 100. The Rebel XSi D-SLR offers an extremely wide range of ISO settings, from 100 to 1600.

Noise and Grain

Noise in digital photography is the equivalent of grain in film photography. It appears as an irregular, sand-like texture that, if large, can be unsightly and, if small, is essentially invisible. (As with grain, this fine-patterned look is sometimes desirable for certain creative effects.) In film, grain occurs due to the chemical structure of the light-sensitive materials. In digital cameras, noise occurs for several reasons: sensor noise (caused by various things, including heat from the electronics and optics), digital artifacts (when digital technology cannot deal with fine tonalities such as sky gradations), and JPEG artifacts (caused by image compression). Of all of these, sensor noise is the most common.

In both film and digital photography, grain or noise emerges when using high ISO speeds. And, on any camera, noise is more obvious with underexposure. With digital cameras, noise may also be increased with long exposures in low-light conditions. The Rebel XSi’s new sensor gathers more light and has improved noise reduction circuitry to minimize digital noise. This technology gives the camera incredible image quality—at high ISOs with low noise—that simply wasn’t possible in the past. This camera also has a number of technologies that create better images with long exposures.

File Formats

A digital camera converts the continuous (or analog) image information from the sensor into digital data. The data may be saved into either of two different digital file formats, RAW or JPEG.

One very useful feature of digital SLRs is their ability to capture a RAW file. RAW files are image files that include information about how the image was shot but have little processing applied by the camera. They also contain 14-bit color information, which is the maximum amount of data available from the sensor. (It is a little confusing that the RAW file format is actually a 16-bit file, though the data from the sensor is 14-bit.) The Rebel XSi uses the CR2 file, the same advanced RAW format developed for the Canon EOS-1D Mark II.

JPEG (Joint Photographic Experts Group) is a standard format for image compression and is the most common file created by digital cameras. Digital cameras use this format because it reduces the size of the file, allowing more pictures to fit on a memory card. It is highly optimized for photographic images.

Both RAW and JPEG files can produce excellent results. The unprocessed data of a RAW file can be helpful when you are faced with tough exposure situations, but the small size of the JPEG file is faster and easier to deal with. It is important to consider that a JPEG image might look great right out of the camera, while a RAW file may need quite a bit of adjustment before the image looks good. When in doubt, the XSi offers the option of recording both RAW and JPEG files of each image.

The Color of Light

Anyone who has shot color slide film in a variety of lighting conditions has horror stories about the color resulting from those conditions. Color reproduction is affected by how a film is balanced or matched to the color of the light. Our eyes adapt to the differences, but film does not.

In practical terms, if you shoot a daylight-balanced (outdoor) film while indoors under incandescent lights, your image will have an orange cast to it. For accurate color reproduction in this instance, you would need to change the film or use a color correction filter. One of the toughest popular lights to balance is fluorescent. The type and age of the bulbs affect their color and how that color appears on film, usually requiring careful filtration. Though filters are helpful in altering and correcting the color of light, they also darken the viewfinder, increase the exposure, and make it harder to focus and compose the image.

With digital cameras, all of this changed. A digital camera acts more like our eyes and creates images with fewer color problems. This is because color correction is managed by the white balance function. White