JPEG - Revision history

Erik Krause: interwiki linked

2007-11-20T16:40:53Z

interwiki linked

Erik Krause: Prepared for new glossary template

2007-11-18T14:37:50Z

Prepared for new glossary template

Bruno: clean up redirecting links

2007-03-15T23:10:54Z

clean up redirecting links

WikiSysop: 8 revision(s)

2006-07-13T20:28:01Z

8 revision(s)

WikiSysop: 1 revision(s)

2006-07-13T19:56:40Z

1 revision(s)

Bruno: categorised

2005-11-11T12:25:23Z

categorised

Bruno: categorised

2005-11-11T12:25:23Z

categorised

New page

'''JPEG''' is an [[Image format|image file format]] for storing and distributing images, particularly photographs.
For a detailed technical overview, please refer to the [http://en.wikipedia.org/wiki/JPEG WikiPedia JPEG page].

'''JPEG''' files typically have a ''.jpg'' file extension.
If you can't see file extensions, you may want to [[enable windows file extensions]]
as you will have great difficulty editing and manipulating image files otherwise.

Digital cameras typically default to saving photographs in '''JPEG''' format as it provides a
good compromise between quality and filesize for most uses.
'''JPEG''' is also a good format for delivering photographic images over the web or in email.

=== Compression issues ===

'''JPEG''' is a ''lossy'' compressed file format, this means that a lot of information that is imperceptable to the human eye is discarded - Converting to another file format will ''not'' restore this missing data.

Unfortunately this degradation can become perceptable if an image is later manipulated, so if you intend to produce high-quality work you might want to switch your camera to take photos in lossless [[TIFF]], [[RAW]] or [[DNG]] format instead.

There are a small number of '''JPEG''' manipulations that can be performed losslessly, such as cropping, rotation (at 90 degree angles), flipping and removal of [[CCD]] artefacts such as ''bad pixels'' (see [http://www.zero-based.org/software/jpegpixi/ Jpegpixi]).

=== EXIF issues ===

Modern cameras save a lot of information about a photograph (time, lens and exposure data) within the '''JPEG''' file as [[EXIF]] data. If you are having trouble, one of these causes may be to blame:

* Rotating a photo may simply flip an [[EXIF]] tag from [[Landscape]] to [[Portrait]] without changing the image itself. The resulting image may or may not appear rotated depending on the viewing software.

* Rotating a photo may rotate the image without changing any [[EXIF]] data to suit, this may cause problems when a GUI tool reads the [[field of view]] from the file. To avoid this, use a tool like [[photomolo]] to do lossless rotation and let it reset the [[EXIF]] tags appropriately.

* Opening and saving a photo may discard all the [[EXIF]] data, switch to another image editor.

=== Color downsampling issues ===

'''JPEG''' isn't an RGB file format where each of three red, green and blue channels are saved alongside each other. A '''JPEG''' image is typically a monochrome image with two lower resolution color channels.

This means that applications where color integrity is important like correcting [[chromatic aberration]] are not suitable uses for '''JPEG''' data.

=== Other JPEG limitations ===

'''JPEG''' doesn't support multiple layers, [[alpha channel]]s or high [[dynamic range]] which means that it isn't much use for ''work in progress'' either. When working with such data, lossless file formats are preferable such as [[PNG]], [[TIFF]], [[PSD]] or [[XCF]].
[[Category:Glossary]]

Bruno: linked to jpegpixi

2005-10-24T17:35:36Z

linked to jpegpixi

Bruno: linkified

2005-10-19T14:48:42Z

linkified

Bruno: link to image format

2005-07-13T10:32:09Z

link to image format

← Older revision		Revision as of 14:37, 18 November 2007
Line 1:		Line 1:
		+	{{Glossary\|Joint Photographic Experts Group wiedely used [[Image format]]}}
	'''JPEG''' is an [[Image format\|image file format]] for storing and distributing images, particularly photographs.		'''JPEG''' is an [[Image format\|image file format]] for storing and distributing images, particularly photographs.
	For a detailed technical overview, please refer to the [http://en.wikipedia.org/wiki/JPEG WikiPedia JPEG page].		For a detailed technical overview, please refer to the [http://en.wikipedia.org/wiki/JPEG WikiPedia JPEG page].

← Older revision		Revision as of 12:25, 11 November 2005
Line 37:		Line 37:

	'''JPEG''' doesn't support multiple layers, [[alpha channel]]s or high [[dynamic range]] which means that it isn't much use for ''work in progress'' either. When working with such data, lossless file formats are preferable such as [[PNG]], [[TIFF]], [[PSD]] or [[XCF]].		'''JPEG''' doesn't support multiple layers, [[alpha channel]]s or high [[dynamic range]] which means that it isn't much use for ''work in progress'' either. When working with such data, lossless file formats are preferable such as [[PNG]], [[TIFF]], [[PSD]] or [[XCF]].
		+	[[Category:Glossary]]

← Older revision		Revision as of 14:48, 19 October 2005
Line 34:		Line 34:
	=== Other JPEG limitations ===		=== Other JPEG limitations ===

−	'''JPEG''' doesn't support multiple layers, alpha ~~channels~~ or high [[dynamic range]] which means that it isn't much use for ''work in progress'' either. When working with such data, lossless file formats are preferable such as [[PNG]], [[TIFF]], [[PSD]] or [[XCF]].	+	'''JPEG''' doesn't support multiple layers, [[alpha channel]]s or high [[dynamic range]] which means that it isn't much use for ''work in progress'' either. When working with such data, lossless file formats are preferable such as [[PNG]], [[TIFF]], [[PSD]] or [[XCF]].

← Older revision		Revision as of 10:32, 13 July 2005
Line 1:		Line 1:
−	'''JPEG''' is a file format for storing and distributing images, particularly photographs.	+	'''JPEG''' is an [[Image format\|image file format]] for storing and distributing images, particularly photographs.
	For a detailed technical overview, please refer to the [http://en.wikipedia.org/wiki/JPEG WikiPedia JPEG page].		For a detailed technical overview, please refer to the [http://en.wikipedia.org/wiki/JPEG WikiPedia JPEG page].

@@ Line 1: / Line 1: @@
 {{Glossary|Joint Photographic Experts Group wiedely used [[Image format]]}}
 '''JPEG''' is an [[Image format|image file format]] for storing and distributing images, particularly photographs.
-For a detailed technical overview, please refer to the [http://en.wikipedia.org/wiki/JPEG WikiPedia JPEG page].
+For a detailed technical overview, please refer to the [[w:JPEG|WikiPedia JPEG page]].
 '''JPEG''' files typically have a ''.jpg'' file extension.

@@ Line 24: / Line 24: @@
 * Rotating a photo may simply flip an [[EXIF]] tag from [[Landscape]] to [[Portrait]] without changing the image itself.  The resulting image may or may not appear rotated depending on the viewing software.
-* Rotating a photo may rotate the image without changing any [[EXIF]] data to suit, this may cause problems when a GUI tool reads the [[field of view]] from the file.  To avoid this, use a tool like [[photomolo]] to do lossless rotation and let it reset the [[EXIF]] tags appropriately.
+* Rotating a photo may rotate the image without changing any [[EXIF]] data to suit, this may cause problems when a GUI tool reads the [[Field of View]] from the file.  To avoid this, use a tool like [[photomolo]] to do lossless rotation and let it reset the [[EXIF]] tags appropriately.
 * Opening and saving a photo may discard all the [[EXIF]] data, switch to another image editor.

← Older revision	Revision as of 20:28, 13 July 2006
(One intermediate revision by one user not shown)

← Older revision		Revision as of 17:35, 24 October 2005
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	Unfortunately this degradation can become perceptable if an image is later manipulated, so if you intend to produce high-quality work you might want to switch your camera to take photos in lossless [[TIFF]], [[RAW]] or [[DNG]] format instead.		Unfortunately this degradation can become perceptable if an image is later manipulated, so if you intend to produce high-quality work you might want to switch your camera to take photos in lossless [[TIFF]], [[RAW]] or [[DNG]] format instead.
		+
		+	There are a small number of '''JPEG''' manipulations that can be performed losslessly, such as cropping, rotation (at 90 degree angles), flipping and removal of [[CCD]] artefacts such as ''bad pixels'' (see [http://www.zero-based.org/software/jpegpixi/ Jpegpixi]).

	=== EXIF issues ===		=== EXIF issues ===