Retaining image size

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Posted By
Niceguy
Nov 13, 2005
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401
Replies
5
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Closed
I have the following problem:
When I have made changes to an existing image (JPEG), and saves it, PS asks me to set the compression ratio. Actually just opening an image and saving it under another name requires this.

All I want is to have the changed image to be of the same quality and thus approx. the same size as the original. In fact I can even set the compression so that the resulting image is larger than the original, which makes no sense, since the quality cannot get better than the original. So please, can anyone explain how to do this or why it is so complicated in PS.

Thanx.
Niceguy
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T
Tacit
Nov 13, 2005
In article <43778cd7$0$8812$>,
"Niceguy" <(removeNOSPAM)> wrote:

When I have made changes to an existing image (JPEG), and saves it, PS asks me to set the compression ratio. Actually just opening an image and saving it under another name requires this.

You’re already making a mistake.

JPEG uses losy compression. It degrades the quality of your image. If you open and then re-save a JPEG, you get cumulative degradation. This is why you never open and re-save a JPEG. When you make an image, always, always save a copy of the original file in some non-degraded file format, like TIFF or PSD.

All I want is to have the changed image to be of the same quality and thus approx. the same size as the original. In fact I can even set the compression so that the resulting image is larger than the original, which makes no sense, since the quality cannot get better than the original. So please, can anyone explain how to do this or why it is so complicated in PS.

You can’t.

You can not open a JPEG and re-save it without re-compressing it and causing additional degradation. This degradation is cumulative and irreversible. Even if you open it and re-save it at maximum quality, you still cause additional, cumulative loss.

The solution to your problem is to save your images twice, once in a lossless format, then go back to your lossless original when you need to make changes or re-save the image.

—
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Niceguy
Nov 13, 2005
"tacit" skrev i en meddelelse
You can not open a JPEG and re-save it without re-compressing it and causing additional degradation. This degradation is cumulative and irreversible. Even if you open it and re-save it at maximum quality, you still cause additional, cumulative loss.

The solution to your problem is to save your images twice, once in a lossless format, then go back to your lossless original when you need to make changes or re-save the image.

Thanks a lot for the quick response, tacit.
I know that JPEG is not giving the best quality pictures.Unfortunately my camera gives no other possibilities than different sizes, but all JPEG 🙁

However I do not understand why it is not possible when saving in PS to select what the resulting image size (in megabytes) should be, and then leave it to the program to set the resolution (while maintaining the height and width of the picture). I see no function like this in CS, or is it just not present when working with JPEG?
R
Roberto
Nov 14, 2005
"Niceguy" <(removeNOSPAM)> wrote"

However I do not understand why it is not possible when saving in PS to select what the resulting image size (in megabytes) should be,

You can, Sir. See this image:
http://elearning.winona.edu/staff_o/jjs/tmp.gif

In File – ‘Save For Web’ find the little arrow shown in the circle I added. Click it and the menu you see there will fly out. Set the file size you want, and save it.
SG
Steve Green
Nov 15, 2005
On Sun, 13 Nov 2005 19:58:06 +0100, "Niceguy"
<(removeNOSPAM)> wrote:

I have the following problem:
When I have made changes to an existing image (JPEG), and saves it, PS asks me to set the compression ratio. Actually just opening an image and saving it under another name requires this.
Mr. Guy:

Your compression issues have been addressed, but to save a file under another name–don’t use PS. Just right-click and "Rename".
BH
Bill Hilton
Nov 17, 2005
I know that JPEG is not giving the best quality pictures.Unfortunately my camera gives no other possibilities than different sizes, but all JPEG 🙁

What many do is open this jpeg and make the edits in Photoshop and then save as a PSD or TIFF so you save as much info as possible. Then if you need to make a jpeg you can make it from this PSD or TIFF but still have a copy of the original with edits. Later if you decide to make more edits (typically after printing) just re-open the PSD or TIFF instead of the jpeg. As Tacit pointed out if you are re-saving and re-compressing jpegs the quality degrades pretty quickly but if you keep the data from the original jpeg intact in a PSD/TIFF file you can minimize this.

Bill

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