Saving JPEG problem

S
Posted By
Stephan
Nov 22, 2004
Views
364
Replies
12
Status
Closed
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

How to Master Sharpening in Photoshop

Give your photos a professional finish with sharpening in Photoshop. Learn to enhance details, create contrast, and prepare your images for print, web, and social media.

E
edjh
Nov 23, 2004
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
E
edjh
Nov 23, 2004
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
S
Stephan
Nov 23, 2004
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.
S
Stephan
Nov 23, 2004
"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
EG
Eric Gill
Nov 23, 2004
"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.
N
nomail
Nov 23, 2004
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/
S
Stephan
Nov 23, 2004
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
S
Stephan
Nov 23, 2004
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
EG
Eric Gill
Nov 23, 2004
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.
F
Fixx
Nov 24, 2004
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
M
Meldon
Nov 26, 2004
"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.
LL
Leonard Lehew
Nov 27, 2004
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

How to Master Sharpening in Photoshop

Give your photos a professional finish with sharpening in Photoshop. Learn to enhance details, create contrast, and prepare your images for print, web, and social media.

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