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Newbie: file size after editing .



 
 
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  #1  
Old November 23rd 04, 01:12 PM
ABC
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Default Newbie: file size after editing .

I notice this with the files I work on. After saving, the file gets
much bigger, although it has the same format.

So I opened a .jpg file of 677k size, did nothing to it and
immediately "save as" in . jpg with a different name. My Photoimpact
7 opened a dialog box and I chose 100% quality so I should have no
loss. The new file is now 1.7M in size but with the same image( in
fact there seemed to be some slight change in the quality)

why is this? how can I get a file of the same size and quality ? Is it
just Photoimpact??

TIA

ABC
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  #2  
Old November 23rd 04, 01:35 PM
Toke Eskildsen
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Default

ABC wrote:

So I opened a .jpg file of 677k size, did nothing to it and
immediately "save as" in . jpg with a different name. My
Photoimpact 7 opened a dialog box and I chose 100% quality so I
should have no loss.


It is still lossy.

http://www.faqs.org/faqs/jpeg-faq/part1/section-13.html

The new file is now 1.7M in size but with the same image( in fact
there seemed to be some slight change in the quality)


You lost a little quality by saving it as a JPEG again.

http://www.faqs.org/faqs/jpeg-faq/part1/section-10.html

why is this? how can I get a file of the same size and quality ?


You can get the same file size by choosing a quality setting that is
about the same as the one your camera uses. As for quality, the you
have to select another format that JPEG.

Is it just Photoimpact??


No, it's all programs that saves as JPEG (except for special programs
that uses lossless conversion for rotation, mirror and crop).
  #3  
Old November 23rd 04, 01:35 PM
Toke Eskildsen
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Posts: n/a
Default

ABC wrote:

So I opened a .jpg file of 677k size, did nothing to it and
immediately "save as" in . jpg with a different name. My
Photoimpact 7 opened a dialog box and I chose 100% quality so I
should have no loss.


It is still lossy.

http://www.faqs.org/faqs/jpeg-faq/part1/section-13.html

The new file is now 1.7M in size but with the same image( in fact
there seemed to be some slight change in the quality)


You lost a little quality by saving it as a JPEG again.

http://www.faqs.org/faqs/jpeg-faq/part1/section-10.html

why is this? how can I get a file of the same size and quality ?


You can get the same file size by choosing a quality setting that is
about the same as the one your camera uses. As for quality, the you
have to select another format that JPEG.

Is it just Photoimpact??


No, it's all programs that saves as JPEG (except for special programs
that uses lossless conversion for rotation, mirror and crop).
  #4  
Old November 23rd 04, 04:35 PM
John McWilliams
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Posts: n/a
Default

Toke Eskildsen wrote:

ABC wrote:


So I opened a .jpg file of 677k size, did nothing to it and
immediately "save as" in . jpg with a different name. My
Photoimpact 7 opened a dialog box and I chose 100% quality so I
should have no loss.



It is still lossy.


Is it just Photoimpact??



No, it's all programs that saves as JPEG (except for special programs
that uses lossless conversion for rotation, mirror and crop).


On a Macintosh at least, using Save As in all programs I have tried,
allows one to rename and change the directory in which the jpeg is
stored. It does not change a pixel. There is no loss in that scenario.

Moreover, the amount of loss is usually tiny after rediting, but can be
avoided easily by saving in the native format of PS, Elements, or PSP.

--
John McWilliams
  #5  
Old November 23rd 04, 05:03 PM
David Hearn
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Default

ABC wrote:
I notice this with the files I work on. After saving, the file gets
much bigger, although it has the same format.

So I opened a .jpg file of 677k size, did nothing to it and
immediately "save as" in . jpg with a different name. My Photoimpact
7 opened a dialog box and I chose 100% quality so I should have no
loss. The new file is now 1.7M in size but with the same image( in
fact there seemed to be some slight change in the quality)

why is this? how can I get a file of the same size and quality ? Is it
just Photoimpact??


JPEG compresses images in a way which means some data is lost - the amount
of data loss is varied by the quality setting. If you chose no compression
then it will be maximum size. What has happened in your situation is that
you've opened a 667k file, which decompresses to about 2MB. When you then
save the image again you have to re-compress the image again to get it back
to 667k - which would require further loss of image data to get it back to
that size. If you chose no compression (or actually, no data loss
compression) then you end up with a 1.7MB file.

This is exactly why people use RAW/lossless image formats, and only save as
JPEG when outputting the final image. Each saving of a jpeg will lose more
and more data (unless no loss is specified, in which case, you get
no/practically no compression).

David


  #6  
Old November 23rd 04, 05:03 PM
David Hearn
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Posts: n/a
Default

ABC wrote:
I notice this with the files I work on. After saving, the file gets
much bigger, although it has the same format.

So I opened a .jpg file of 677k size, did nothing to it and
immediately "save as" in . jpg with a different name. My Photoimpact
7 opened a dialog box and I chose 100% quality so I should have no
loss. The new file is now 1.7M in size but with the same image( in
fact there seemed to be some slight change in the quality)

why is this? how can I get a file of the same size and quality ? Is it
just Photoimpact??


JPEG compresses images in a way which means some data is lost - the amount
of data loss is varied by the quality setting. If you chose no compression
then it will be maximum size. What has happened in your situation is that
you've opened a 667k file, which decompresses to about 2MB. When you then
save the image again you have to re-compress the image again to get it back
to 667k - which would require further loss of image data to get it back to
that size. If you chose no compression (or actually, no data loss
compression) then you end up with a 1.7MB file.

This is exactly why people use RAW/lossless image formats, and only save as
JPEG when outputting the final image. Each saving of a jpeg will lose more
and more data (unless no loss is specified, in which case, you get
no/practically no compression).

David


  #7  
Old November 24th 04, 01:35 AM
ABC
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Posts: n/a
Default

This is the answer. Thanks.

would tiff solve my problem? I do not think my camera has RAW.


On Tue, 23 Nov 2004 17:03:31 -0000, "David Hearn"
wrotd:

JPEG compresses images in a way which means some data is lost - the amount
of data loss is varied by the quality setting. If you chose no compression
then it will be maximum size. What has happened in your situation is that
you've opened a 667k file, which decompresses to about 2MB. When you then
save the image again you have to re-compress the image again to get it back
to 667k - which would require further loss of image data to get it back to
that size. If you chose no compression (or actually, no data loss
compression) then you end up with a 1.7MB file.

This is exactly why people use RAW/lossless image formats, and only save as
JPEG when outputting the final image. Each saving of a jpeg will lose more
and more data (unless no loss is specified, in which case, you get
no/practically no compression).

David



ABC
Do not reply by email.


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  #8  
Old November 24th 04, 01:35 AM
ABC
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Posts: n/a
Default

This is the answer. Thanks.

would tiff solve my problem? I do not think my camera has RAW.


On Tue, 23 Nov 2004 17:03:31 -0000, "David Hearn"
wrotd:

JPEG compresses images in a way which means some data is lost - the amount
of data loss is varied by the quality setting. If you chose no compression
then it will be maximum size. What has happened in your situation is that
you've opened a 667k file, which decompresses to about 2MB. When you then
save the image again you have to re-compress the image again to get it back
to 667k - which would require further loss of image data to get it back to
that size. If you chose no compression (or actually, no data loss
compression) then you end up with a 1.7MB file.

This is exactly why people use RAW/lossless image formats, and only save as
JPEG when outputting the final image. Each saving of a jpeg will lose more
and more data (unless no loss is specified, in which case, you get
no/practically no compression).

David



ABC
Do not reply by email.


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  #9  
Old March 3rd 05, 07:30 PM
DM
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Posts: n/a
Default

Convert the original JPG to TIF whilst editing & only convert back to JPG
when you're sure you have your 'final' image

Regards

DM

"ABC" wrote in message
news
This is the answer. Thanks.

would tiff solve my problem? I do not think my camera has RAW.


On Tue, 23 Nov 2004 17:03:31 -0000, "David Hearn"
wrotd:

JPEG compresses images in a way which means some data is lost - the amount
of data loss is varied by the quality setting. If you chose no
compression
then it will be maximum size. What has happened in your situation is that
you've opened a 667k file, which decompresses to about 2MB. When you then
save the image again you have to re-compress the image again to get it
back
to 667k - which would require further loss of image data to get it back to
that size. If you chose no compression (or actually, no data loss
compression) then you end up with a 1.7MB file.

This is exactly why people use RAW/lossless image formats, and only save
as
JPEG when outputting the final image. Each saving of a jpeg will lose
more
and more data (unless no loss is specified, in which case, you get
no/practically no compression).

David



ABC
Do not reply by email.


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News==----
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Newsgroups
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