Quality Settings

You can choose the image quality settings used by the XTi to store its files. You have three choices to make:

■ Resolution. The number of pixels captured determines the absolute resolution of the photos you shoot with your Digital Rebel XTi. Your choices range from 10 megapixels (Large, or L), measuring 3888 X 2592 pixels; 5.3 megapixels (Medium, or M), measuring 2816 X 1880 pixels; to 2.5 megapixels (Small, or S), measuring 1936 X 1288 pixels.

■ JPEG compression. To reduce the size of your image files and allow more photos to be stored on a given Compact Flash card, the XTi uses JPEG compression to squeeze the images down to a smaller size. This compacting reduces the image quality a little, so you're offered the choice of Fine compression or Normal compression. The symbols help you remember that Fine compression (represented by a quarter-circle) provides the smoothest results, while Normal compression (signified by a stair-step icon) provides "jaggier" images.

■ JPEG, RAW, or both. You can elect to store only JPEG versions of the images you shoot, or you can save your photos as uncompressed, loss-free RAW files, which consume more than twice as much space on your memory card. Many photographers elect to save both versions, so they'll have a JPEG version that might be usable as-is, as well as the original "digital negative" RAW file in case they want to do some processing of the image later. You'll end up with two different versions of the same file: one with a .jpg extension, and one with the .cr2 extension that signifies a Canon RAW file. When you choose RAW+JPEG, the JPEG file is always stored using the FINE compression setting.

To choose the combination you want, access the menus, scroll to Quality, and press the Set button. A screen similar to the one shown in Figure 3.2 will appear. Use the cross keys or Main Dial to cycle among the eight choices. In practice, you'll probably use only the Large-Fine, RAW+Large Fine, or RAW selections.

Why so many choices, then? There are some limited advantages to using the Medium and Small resolution settings and Normal JPEG compression setting. They allow stretching the capacity of your Compact Flash card so you can shoehorn quite a few more pictures onto a single memory card. That can come in useful when on vacation and you're running out of storage, or when you're shooting non-critical work that doesn't require a full 10 megapixels of resolution (such as photos taken for real estate listings, web page display, photo ID cards, or similar applications). Some photographers like to record RAW+JPEG so they'll have a moderate quality JPEG file for review only, while retaining access to the original RAW file for serious editing.

However, for most work, using lower resolution and extra compression is false economy. You never know when you might actually need that extra bit of picture detail. Your best bet is to have enough memory cards to handle all the shooting you want to do until you have the chance to transfer your photos to your computer or a personal storage device.

Reduced image quality can also sometimes be beneficial if you're shooting sequences of photos rapidly, as the XTi is able to hold more of them in its internal memory buffer before transferring to the Compact Flash card. Still, for most sports and other applications, you'd probably rather have better, sharper pictures than longer periods of continuous shooting.

Figure 3.2 Choose your resolution, JPEG compression, and file format (Large/Fine JPEG in this case) from this screen.

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You'll sometimes be told that RAW files are the "unprocessed" image information your camera produces, before it has been modified. That's nonsense. RAW files are no more unprocessed than your camera film is after it's been through the chemicals to produce a negative or transparency. A lot can happen in the developer that can affect the quality of a film image—positively and negatively—and, similarly, your digital image undergoes a significant amount of processing before it is saved as a RAW file. Canon even applies a name (Digic II) to the digital image processing (DIP) chip used to perform this magic.

A RAW file is more similar to a film camera's processed negative. It contains all the information, captured in 12-bit channels per color (and stored in a 16-bit space), with no compression, no sharpening, no application of any special filters or other settings you might have specified when you took the picture. Those settings are stored with the RAW file so they can be applied when the image is converted to a form compatible with your favorite image editor. However, using RAW conversion software such as Adobe Camera Raw or Canon's Digital Photo Professional, you can override those settings and apply settings of your own. You can select essentially the same changes there that you might have specified in your camera's picture-taking options in creating a new file that leaves the original RAW file untouched.

RAW exists because sometimes we want to have access to all the information captured by the camera, before the camera's internal logic has processed it and converted the image to a standard file format. RAW doesn't save space like JPEG. But it preserves all the information captured by your camera after it has been converted from analog to digital form.

So, why don't we always use RAW? Although some photographers do save only in RAW format, it's more common to use either RAW plus one JPEG Fine, or just shoot JPEG and eschew RAW altogether. While RAW is overwhelmingly helpful when an image needs to be fine-tuned, in other situations working with a RAW file can slow you down significantly. RAW images take longer to store on the Compact Flash card, and they require more post-processing effort, whether you elect to go with the default settings in force when the picture was taken, or make minor adjustments.

As a result, those who depend on speedy access to images or who shoot large numbers of photos at once may prefer JPEG over RAW. Wedding photographers, for example, might expose several thousand photos during a bridal affair and offer hundreds to clients as electronic proofs for inclusion in an album. Wedding shooters take the time to ensure that their in-camera settings are correct, minimizing the need to post-process photos after the event. Given that their JPEGs are so good, there is little need to get bogged down shooting RAW. JPEG was invented as a more compact file format that can store most of the information in a digital image, but in a much smaller size. JPEG predates most digital SLRs, and was initially used to squeeze down files for transmission over slow dialup connections. Even if you were using an early dSLR with 1.3-megapixel files for news photography, you didn't want to send them back to the office over a modem at 1200 bps uncompressed.

But, as I noted, JPEG provides smaller files by compressing the information in a way that loses some image data. JPEG remains a viable alternative because it offers several different quality levels. At the highest quality Fine level, you might not be able to tell the difference between the original RAW file and the JPEG version, even though the RAW file occupies, by Canon's estimate, 9.8 MB on your memory card, while the Fine JPEG takes up only 3.8 MB of space. You've squeezed the image by more than half without losing much visual information at all. If you don't mind losing some quality, you can use more aggressive Normal compression with JPEG to cut the size in half again, to 2.0 MB. In my case, I shoot virtually everything at RAW+JPEG. Most of the time, I'm not concerned about filling up my memory cards, because I usually have a minimum of 15 GB worth of Compact Flash cards with me. If I know I may fill up all those cards, I have a tiny battery-operated personal storage device that can copy a 4 GB card in about eight minutes. Sometimes when shooting sports, I'll shift to JPEG FINE (with no RAW file) to squeeze a little extra speed out of my XTi's continuous shooting mode, and to reduce the need to wade through eight-photo bursts taken in RAW format. On the other hand, on my last trip to Europe, I took only RAW (instead of my customary RAW+JPEG) photos to fit more images onto my 60 GB personal storage device, shown in Figure 3.3, as I planned on doing at least some post-processing on many of Figure 3.3 If RAW storage space is a concern, consider a portable the images for a travel book I was working storage device like this one.

MANAGING LOTS OF FILES

The only long-term drawback to shooting everything in RAW+JPEG is that it's easy to fill up your computer's hard drive if you are a prolific photographer. Here's what I do. My most recent photos are stored on my working hard drive in a numbered folder, say XTi-01, with subfolders named after the shooting session, such as 080301Trees, for pictures of trees taken on March 1, 2008. An automatic utility copies new and modified photos to a different hard drive for temporary backup four times daily.

When the top-level folder accumulates about 30 GB of images, I back it up to DVDs and then move the folder to a 500 GB drive dedicated solely for storage of folders that have already been backed up onto DVD. Then I start a new folder, such as XTi-02, on the working hard drive and repeat the process. I always have at least one backup of every image taken, either on another hard drive or on a DVD.

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Digital Camera and Digital Photography

Digital Camera and Digital Photography

Compared to film cameras, digital cameras are easy to use, fun and extremely versatile. Every day there’s more features being designed. Whether you have the cheapest model or a high end model, digital cameras can do an endless number of things. Let’s look at how to get the most out of your digital camera.

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