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digital basics
Format
Compression
amount
Original
file size
Compressed
file size
Lossy/
Lossless
JPEG Minimum
20.0MB
(PSD file)
0.14MB
Lossy
JPEG Maximum
2.86MB
Lossy
JPEG2000
Minimum
0.07MB
Lossy
JPEG2000
Maximum
2.54MB
Lossy
JPEG2000
–
5.40MB
Lossless
TIFF
LZW
10.30MB
Lossless
TIFF
Zip
10.10MB
Lossless
TIFF
None
27.30MB
Lossless
PSD
–
20.00MB
Lossless
/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.
Comparing the
compression abilities
of different file types
and settings using the
same 20MB base file
Typical artifacts resulting from applying too much compression to a photo