Saving JPEG problem

Stephan wrote:

Hi group,

Something I noticed but never bothered me…until now 🙁 I open a JPEG, duplicate it and save the copy using Quality 12 (maximum) Why is the copy so much bigger than the original? 2,700 KB becomes 3,190 KB I am assembling JPEGs in a Stitching application and it refuses my copies because they do not have the same size than the originals. What is PS adding to the file?
How can I save copies, edited or not, so they have the exact same size than the original?

Aloha,

Stephan

Use Save for Web. It won’t add any data. In the 4 up choose the quality setting you want, probably High.

—
Comic book sketches and artwork:
http://www.sover.net/~hannigan/edjh.html
Comics art for sale:
http://www.sover.net/~hannigan/batsale.html

edjh wrote:

Stephan wrote:

Hi group,

Something I noticed but never bothered me…until now 🙁 I open a JPEG, duplicate it and save the copy using Quality 12 (maximum) Why is the copy so much bigger than the original? 2,700 KB becomes 3,190 KB
I am assembling JPEGs in a Stitching application and it refuses my copies because they do not have the same size than the originals. What is PS adding to the file?
How can I save copies, edited or not, so they have the exact same size than
the original?

Aloha,

Stephan

Use Save for Web. It won’t add any data. In the 4 up choose the quality setting you want, probably High.

I would also question why you are opening and resaving. If you want the same file just copy it without opening. Resaving jpg degrades quality.

—
Comic book sketches and artwork:
http://www.sover.net/~hannigan/edjh.html
Comics art for sale:
http://www.sover.net/~hannigan/batsale.html

Use Save for Web. It won’t add any data. In the 4 up choose the quality setting you want, probably High.

I would also question why you are opening and resaving. If you want the same file just copy it without opening. Resaving jpg degrades quality.

Thanks, I have to see what Save for Web does.
I just saved without changing anything to test, otherwise I do change things to the file.
BTW, opening and closing a JPEG does NOT degrade it in any way.

I still wonder what PS does to a file when saving it.

Stephan.

"edjh" wrote in message

Stephan wrote:

Hi group,

Something I noticed but never bothered me…until now 🙁 I open a JPEG, duplicate it and save the copy using Quality 12 (maximum) Why is the copy so much bigger than the original? 2,700 KB becomes 3,190

KB

I am assembling JPEGs in a Stitching application and it refuses my

copies

because they do not have the same size than the originals. What is PS adding to the file?
How can I save copies, edited or not, so they have the exact same size

than

the original?

Aloha,

Stephan

Use Save for Web. It won’t add any data. In the 4 up choose the quality setting you want, probably High.

2,700 KB Saved for Web
High –> 591KB
Very High –> 1,163KB
Max –> 3,016KB

Where do the additional 316KB come from?

Stephan

"Stephan" wrote in news:tgwod.12444$Uj.8264
@twister.socal.rr.com:

I still wonder what PS does to a file when saving it.

Recompresses the data it decompressed for editing.

The original compression has little bearing on the final file size.

You will *never* get exactly the original file size with a lossy compression scheme. Period.

Stephan wrote:

2,700 KB Saved for Web
High –> 591KB
Very High –> 1,163KB
Max –> 3,016KB

Where do the additional 316KB come from?

From the fact that "max" uses less compression than the original compression of your file. It’s like squeezing a sponge, but this time you sqeezed a little less. Why is that so hard to understand?

—
Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/

Eric Gill wrote:

"Stephan" wrote in news:tgwod.12444$Uj.8264
@twister.socal.rr.com:

I still wonder what PS does to a file when saving it.

Recompresses the data it decompressed for editing.

The original compression has little bearing on the final file size.
You will *never* get exactly the original file size with a lossy compression scheme. Period.

I understand that now but lossy means losing something and I end up with more.

Stephan

Johan W. Elzenga wrote:

Stephan wrote:

2,700 KB Saved for Web
High –> 591KB
Very High –> 1,163KB
Max –> 3,016KB

Where do the additional 316KB come from?

From the fact that "max" uses less compression than the original compression of your file. It’s like squeezing a sponge, but this time you sqeezed a little less.

OK now I got it
Thank you.

Why is that so hard to understand?

Oh I don’t know… Maybe I’m getting stupid as I get older.

Stephan

Stephan wrote in news:jVKod.59096$hN1.57982
@twister.socal.rr.com:

Eric Gill wrote:

"Stephan" wrote in news:tgwod.12444$Uj.8264
@twister.socal.rr.com:

I still wonder what PS does to a file when saving it.

Recompresses the data it decompressed for editing.

The original compression has little bearing on the final file size.
You will *never* get exactly the original file size with a lossy compression scheme. Period.

I understand that now but lossy means losing something and I end up with more.

You lost information. As un-technically as possible, JPEG creates a less- detailed approximation of your image.

The amount of pixels is the same, which you then apply a lesser degree of compression to and wind up with a larger file.

In article ,
Eric Gill wrote:

I understand that now but lossy means losing something and I end up with more.

You lost information. As un-technically as possible, JPEG creates a less- detailed approximation of your image.

The amount of pixels is the same, which you then apply a lesser degree of compression to and wind up with a larger file.

And losing information is cumulative, each time you recompress you lose more information i.e. quality — even if datasize grows. -F

"Stephan" wrote in message

…

Oh I don’t know… Maybe I’m getting stupid as I get older.

Stephan

It seems we’re all learning things.

On Mon, 22 Nov 2004 23:58:12 GMT, "Stephan"
wrote:

Hi group,

Something I noticed but never bothered me…until now 🙁 I open a JPEG, duplicate it and save the copy using Quality 12 (maximum) Why is the copy so much bigger than the original? 2,700 KB becomes 3,190 KB I am assembling JPEGs in a Stitching application and it refuses my copies because they do not have the same size than the originals. What is PS adding to the file?
How can I save copies, edited or not, so they have the exact same size than the original?

Aloha,

Stephan

When you opened the original file, it was un-compressed into your computer’s main memory (RAM). Suppose the original image was 3000 x 4000 pixels with 8 bits per pixel. The uncompressed image occupies about 12 million bytes of memory. (3000 X 4000 X 8 bits / 8 bits/byte). When you saved it, the editing program sampled the in-memory copy of the file to produce a new JPEG file. The size of the new file is a function of the data in the file and the amount of compression you applied. It is pretty much unrelated to the size of of the original file.

Cheers,

Leonard