Digital Photo Magic: Easy Image Retouching and Restoration for Librarians, Archivists, & Teachers by Ernest Perez

Author:Ernest Perez [Perez, Ernest]
Language: eng
Format: epub
Publisher: Information Today, Inc.
Published: 2016-02-07T23:00:00+00:00

Figure 4.1illustrates a suggested post-processing workflow based on standardized use of PNG lossless compression digital image files to minimize image editing degradation. At the beginning of the processing, non-PNG files are converted to PNG format, and hardcopy original photo prints or graphic images are scanned to PNG files. These are then directed into the same main post-processing workflow. At the end, PNG files can be converted to another digital image format that is required or preferred.

•Use a file conversion utility to transform an original JPEG file directly to PNG. A conversion utility generally will not add extraneous space during a conversion to a new PNG file. Above all, don’t use the “Save As” operation in your photo editor for file conversion. “So with a JPEG that has been converted to PNG you will often get a larger file in kbytes than if you would have gone to PNG to begin with. In other words, it lowers the efficiency of the PNG compression.” (Although Chastain doesn’t mention it, I like NCH Software’s freeware Pixillon Image Converter, a link to which is available on the DPM website.)

•Chastain states that repeated JPEG file saves don’t really add all that much cumulative image degradation if you consistently use a high-quality setting of JPEG compression, such as 95% or 100%. However, if you ever save any intermediate version of your work at a lower quality compression—for example, at 70%—you’ll permanently lose image detail. Saving it later at 95% or 100% does not recapture the lost detail (Chastain, 2013a).

•She recommends using only a lossless format master copy in a format such as PNG or TIFF for any important archival storage, especially for files that you expect to edit again for future use. JPEG images lose quality each time they are opened, edited, and saved again, so you should avoid archiving with this format. Always keep a lossless master copy of any image you expect to edit again. JPEG, she says, should only be used for archival storage when disk space is your primary consideration. (Given the low cost of today’s storage space I don’t think it should be: my Hitachi SimpleTech 500 GB external disk drive, for example, cost just $70 during the Christmas sale season of 2012.)

•Chastain recommends PNG as a good archival alternative, because PNG files are considerably smaller than TIFF or BMP files. She writes, “PNG is an excellent choice for archiving. In fact, I use PNG for almost everything, especially when I need to port images between various programs” (Chastain, 2013b).

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