Compressed Image Files

Our full resolution digital images tend to be very large files. A typical image file for one of our full resolution photos might be as large as 15 megabytes in uncompressed Tagged Image Format (.tif). We frequently encounter customer Internet Service Providers (ISPs) that limit e-mail attached file size to about 10 megabytes per e-mail. We have rarely encountered ISPs that do not allow e-mail attached files as small as 5 megabytes. We cannot send e-mail from our ISP with attachment files larger than about 11 megabytes per e-mail.  Because of attached file size limitations with ISPs, e-mail delivery requires that most of our image files be delivered in compressed image file formats.

Compressed image file formats are computer image files that are compressed to smaller file size in the file saving process (smaller size = fewer megabytes).  Compressed image format files, with their resulting smaller file sizes, are far more likely to be within the sizes allowed for computer file attachment to e-mail by Internet Service Providers (ISPs). In addition to being easier to e-mail, compressed image format files upload and download faster, as well as taking much less space to store on computer hard drives. Compressed image files come in two basic types, lossless compressed image file formats and lossy compressed image file formats.

Lossless compressed image format files are much smaller than uncompressed format files of the same image are. Lossless compressed image formats open in image editing software (Photoshop, Photoshop Elements, Paint Shop Pro and many others) to be a full sized, uncompressed version of the image and are said to have identical quality to the image gained using an uncompressed file version of the same image (lossless = no image information loss during the file saving compression process). Once opened in image editing software, lossless compressed image format files can be resaved in uncompressed image file formats, such as uncompressed Tagged Image Format (.tif). In this way, you can receive an e-mailed version of one of our images that should be identical to the uncompressed Tagged Image Format (.tif) file we might send you on a CD through the mail. E-mailed files get to you far more quickly though, via what is normally an easier process for all concerned and come to you without postage and handling charges. Common lossless formats available from us include lossless LZW compressed Tagged Image Format (.tif), lossless JPEG 2000 (.jp2) and lossless JPEG (.jpg). Our experience indicates lossless JPEG 2000 format files are especially compact compared to other lossless compressed image file formats we have encountered.

Lossy compressed file formats are compressed in the file saving process to smaller file size than uncompressed file formats and lossless compressed file formats. Lossy compressed image file formats provide the smallest file sizes for a given image but lose some of the image information in the compression process. A lossy file format version of an image opens in image editing software to be a full resolution version of the image with lower quality than uncompressed and lossless compressed versions of the same image. Quality losses are probably least, for the smallest size of file gained through file compression, with lossy JPEG 2000 format (.jp2). Our experience indicates, however, that almost all image editing software supports use of standard lossy JPEG format (.jpg) image files. Lossy JPEG format files, with up to 8:1 compression, normally can provide images with loss of image quality that is very hard to see. JPEG files with as little as 3:1 compression are still very compact and normally have excellent image quality.

Some versions of Photoshop do not support JPEG 2000 and some other common image formats with the default installation of that software. A plug-in program on the Photoshop CS setup disk, for example, can be installed from the software's installation disk to make using a wider variety image file formats possible with Photoshop. Information about image format file support can normally be found within your software' documentation or at the software manufacturer's web site. Support software for using many common image file formats may also be available for download from your software manufacturer's web site.

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