Photoshop CS3

digital basics

Compression amount

Original file size

Compressed file size

Lossy/ Lossless

Format

JPEG Minimum JPEG Maximum

0.14MB 2.86MB 0.07MB 2.54MB 5.40MB 10.30MB 10.10MB 27.30MB 20.00MB

Lossy Lossy Lossy Lossy

JPEG2000 JPEG2000 JPEG2000

Minimum Maximum

20.0MB (PSD file)

–

Lossless Lossless Lossless Lossless Lossless

TIFF TIFF TIFF PSD

LZW

Comparing the compression abilities of different file types and settings using the same 20MB base file

Zip

None

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/V^ SVZZ` PZ SVZZ`& The term lossy means that some of the image’s quality is lost in the compression process. The amount and type of compression used determines the look of the end result. Standard JPEG and JPEG2000 display different types of ‘artifacts’ or areas where compression is apparent. The level of acceptable artifacts and practical file sizes will depend on the required outcome for the picture. To help ensure that you have the best balance of file size and image quality make sure that you: Use the Save for Web or Save As > JPEG2000 features – both contain a post-compression t preview option. Always examine the compressed image at a magnification of 100% or greater so that t unacceptable artifacts will be obvious.

Typical artifacts resulting from applying too much compression to a photo

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