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Whale photo-identification: Digital photography techniques, using EXIF data, and photo editing tools

When whale photo-identification studies first began in the 1960s and 1970s, researchers used either 35mm slide film or high resolution black and white film to document individual whales. Some photo-ID programs evaluated negatives magnified with dissecting microscope to look for matches and other programs made custom black and white prints in a photo darkroom, carefully enlarging, rotating and adjusting each image to bring out all the fine detail on the negative.

Today's digital photography equivalent of a film negative is the RAW format image file. RAW images are the most accurate photo record that your camera can produce. Because RAW files can’t be modified, they are akin to a negative and must be processed to use them effectively (see Appendix I for a description of some common image file types).

JPEG format files should not be used in the field for photo-ID photos. The JPEG format does not capture the reality of the image nearly as well as the RAWformat. It does not contain detail that can be edited if the lighting is poor or the animal is distant, and JPEG compression algorithms can tend to add digital artifacts (erroneous markings) that show when the image has been enlarged (see Appendix II).

Recent advances in photo editing tools allow us to work directly (and efficiently) with RAW files rather than having to pre-process RAW files using the digital camera’s software tools. Photo editing tools now allow users to view, edit and “Batch Convert File Format” to convert RAW files (7-15 Mbytes on average) to “best compressed” JPEG files (about 300-600 Kbytes on average). These compressed JPEG files show an amazing amount of detail even when enlarged over 200%. And if the quality of the compressed JPEG is not sufficient, the RAW file can be edited and re-converted to compressed JPEG.

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Whale photo-identification: Digital photography techniques, using EXIF data, and photo editing tools