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Hack 28 Analyze Metadata to Improve Your Shots
In the days of film cameras, I seldom recorded exposure settings that would have helped me better analyze my pictures. Now, digital
Every time you click the shutter, your digital camera records
In essence, each picture file contains a complete photographic history of the
2.14.1 What Is EXIF?
The EXIF format is an international specification, first established in 1995, that enables digital cameras (and other imaging devices) to write data to the file header of the image. EXIF files use the JPEG DCT format specified in ISO/IEC 10918-1. The picture portion of the file can be read by any application supporting JPEG, including web browsers and image editors. The metadata can be accessed by applications designed to extract that information out of the header and display it. The most common imaging applications have no problem displaying at least some of the EXIF data.
However, the picture file usually contains more information than what's typically displayed by a given application, unless that application is designed
But iPhoto doesn't provide you with other data sitting there in the file header, such as white balance. If you need that information, you have to
2.14.2 Why Would I Want to Read EXIF Data?
When you take pictures, some
If you look at a picture of running water, for example, and you like the way it's rendered, wouldn't it be nice to know the settings that you used, so you could duplicate the effect? Before digital cameras were available, I would take
I know that I can control the way water appears by adjusting the shutter speed. The 1/250-of-a-second exposure "
Time of day also has a dramatic impact on pictures. (Make sure you have your camera's time and date settings correct so that they are accurately recorded with the picture.) Over the course of a few hours, a scene can totally change in appearance. When I checked the metadata for Figure 2-22 in iPhoto, it said that the image was captured at 10:45 a.m. The shot in Figure 2-23, from
Even though these pictures were captured from roughly the same location, only a day apart, they are very different. The sun was higher in the first picture and it flattened out the scene, rendering more even highlights and shadows. The same picture shot two and a half hours earlier on the following day shows the difference when the sun is lower and creates harsher highlights and shadow areas.
If I were to go back to these lakes at the same time next year, I could then determine what time to start shooting based on my review of the metadata for the pictures I'd already taken. If I wanted more even, less dramatic lighting, then late morning seems ideal for that effect. On the other hand, if I like the harsher contrast of darks and lights, then I know I have to get there a few hours earlier.
Figure 2-22. The lake at 10:45 a.m.
Figure 2-23. The lake at 8:15 a.m.
These are just a couple ways to review EXIF data to analyze your pictures. Other settingssuch as flash on or off, exposure compensation, white balance, and aperture setting (for depth of field)are all important clues to understanding the success or failure of your images.
2.14.3 What Should I Use to View EXIF Data?
You have many options for viewing the EXIF data your camera captures. As I mentioned before, digital shoeboxes such as Adobe Album, iPhoto, and iView Media Pro provide you with most of the important information that you commonly need. Also, take a look at the software bundled with your camera. For example, both Nikon and Canon provide image utilities that are pretty good at displaying the data your camera captures. A good universal tool is Photoshop Elements, which can serve as your
Figure 2-24. Viewing EXIF data in Photoshop's File Browser
This application shows me settings, such as white balance, that aren't displayed in more basic image editors. I don't always need this level of detail, but it's nice to know it's there if I want it.
2.14.4 Final Thoughts
I recommend you keep a set of original files for all of your important images. In part, I think this is just good file management. But I also like to have those original pictures because I know that the metadata will be intact for me to review whenever I want it.
When you manipulate pictures and save them in optimized formats, important metadata is sometimes removed from the header. If you don't have those original files to fall back on, you might lose that information forever. Plus, it's always wise to have the unaltered, uncropped picture stashed away safe and sound.
This hack just scratches the surface of metadata use. Soon, GPS-equipped cameras might be able to record positioning coordinates to the EXIF file, which could later be translated into locations when browsed with the image editor. Who
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