In the days of film cameras, I seldom recorded exposure settings that would have helped me better analyze my pictures. Now, digital cameras handle all that work for me, and I can use that information to figure out what went right or what went wrong.
Every time you click the shutter, your digital camera records valuable picture data that describes the image you just captured. Data such as time, shutter speed, aperture, focal length, and ISO are written to the file header in the Exchangeable Image File (EXIF) format. This information becomes part of the total image file and can be displayed with applications such as Photoshop.
In essence, each picture file contains a complete photographic history of the decisive moment, which can be analyzed to help you understand why the image was successful or give you clues as to what went wrong. In this hack, I'll show you how to retrieve this data and use it to perfect your photography portfolio skills.
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 specifically to output EXIF information. For example, iPhoto on the Mac provides the basic time, date, file size, and camera information when you click on the Photo tab of the Show Info window. If you click on the Exposure tab, you get more data, such as shutter speed, aperture, focal length, exposure compensation, metering pattern, and flash status.
But iPhoto doesn't provide you with other data sitting there in the file header, such as whit balance. If you need that information, you have to open the file with another application designed to grab that data. The point is that the EXIF specification dictates what goes in to the picture file, but image editors typically give you only a portion of that information. So, if you get serious about reading this stuff, you might need to add a couple tools to your imaging bag of tricks.
Why Would I Want to Read EXIF Data?
When you take pictures, some turn out better than others. Why is that? Beyond good composition and subject matter, there are many factors that contribute to powerful images. These include time of day, depth of field, proper shutter speed, and exposure compensation as needed.
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 handwritten notes to help me remember the settings for particular shots. I hated that! Now, the camera records all that information for me, and I'm free to concentrate on taking good pictures.
I know that I can control the way water appears by adjusting the shutter speed. The 1/250-of-a-second exposure "stopped the action" to some degree and the 1-second exposure created a soft look. Now, the next time I shoot running water, I can capture the exact effect I want by adjusting the shutter speed.
Source: O’Reiley | Website for Photographers | Portfolio website for students
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