1. What are the optimal settings for my image capture devices to promote saving the images, including moving them through several environments? Brew a strong pot of coffee and read on.
After much reading… if you’re going to preserve digital image files, they should 1) be high resolution, 2) contain all of the original pixels, 3) have been minimally manipulated (or not at all), 4) be in a format that accommodates 1) and 2), and 5) be in a format that is not hardware- or software-dependent. The successful combination of these factors should result in a file that can migrate across multiple environments and be viewed in standard image software or on the web.
In the case of my Sony DSC-W5:
- The image should be high resolution: The image size should be as large as possible. For this camera, that setting is 5M. Other options were 3M, 1M or VGA.
- The image should contain all of its pixels: Briefly, the compression should be low in order to record a high quality picture. This setting is Fine (FINE in the menu).
- The image should be minimally manipulated: Move images regularly off the camera into an appropriately named folder on a computer (e.g., yyyymm_archiveImages). I’ll discuss other storage steps elsewhere. If there are images to manipulate, copy them to a separate folder (e.g., yyyymm_workingImages). There is much discussion about the extent to which you can manipulate and save files without experiencing degradation. I’ll save that for the detailed workflow process. In short: Do NOT import directly into iPhoto or image viewer programs. Do NOT use the manufacturer’s software to manage images. Do NOT save the photos to a MyAnything folder. DO establish your own folder structure and transfer the files from camera to computer.
- The image should be in a format that accommodates 1) high resolution and 2) low compression: The Sony DSC-W5 creates JPEG files, so I have to make do. Some digital cameras create RAW files, which are proprietary to the manufacturer and therefore in conflict with 5)…
- The image should be in a format that is not hardware- or software-dependent: While JPEG is a common format, TIFF or JPEG2000 would be best. There are lots of resources that explain the differences between image file formats, but the US Library of Congress has a great page of Format Descriptions for Still Images. Also, the UPDIG Photographers Guidelines have a great discussion of archiving with regard to formats from a professional photographer’s point of view. Mad props to Ken Fleisher and Peter Krogh for this work.
Less briefly, digital images are comprised of pixels, and each pixel contains 3 bytes of data to capture red, green, and blue. An image that contains all of its bytes creates a large file. The more you compress the pixels, the smaller the file but the more information about the image you lose. A lossless compression algorithm discards no information. It looks for more efficient ways to represent an image, while making no compromises in accuracy. In contrast, lossy algorithms accept some degradation in the image in order to achieve smaller file size. It’s difficult to talk about compression without veering into details of camera sensors, image structure, file formats, etc. I gathered basic info from Bob Atkins’ and Rick Matthews’ sites, but there is a gloriously detailed discussion of color sampling, albeit for video, from Karl Soule.
Summary: I’ve configured my camera to ensure the best quality images for preservation. However, I can’t be guaranteed that the JPEG format will continue to be a standard in the future. If converting the JPEG images to TIFF won’t increase the image quality (but might increase the file size, requiring more storage – something to test), then the only reason to convert all of my images to TIFFs is to feel secure that I’ve done everything possible, at the file level, to ensure their preservation. And, even if the files are converted to TIFFs, I’ll continue to not overwrite the JPEG images on the storage Memory Stick(s), I’ll continue to store the original JPEG images in separate archival folders, and I’ll continue to backup those folders in different locations. Is it worth it to replicate this process for TIFF files? I’m not sure. More in the next installment…
An excellent read from the Library of Congress: Guidelines for Electronic Preservation of Visual Materials