Is CS altering my images without me knowing it?

When i open a JPEG from my camera the file is approx 2Mb, but when i then save it from Adobe Photoshop CS with maximum compression the file gets up to mayby 6 Mb. Why?

Is there a way to get Photoshop to choose the same quality as i opened the JPEG in?

I would be very thankful for any help (as some of you might have guessed i am a complete newbie )

Erik

It's not altering the picture but it stores info that all other programs don't. If you opened the same picture in Windows or PSP it would only be 2Mb.

Dikim said:

When i open a JPEG from my camera the file is approx 2Mb, but when
i then save it from Adobe Photoshop CS with maximum compression the
file gets up to mayby 6 Mb. Why?

Is there a way to get Photoshop to choose the same quality as i
opened the JPEG in?

I would be very thankful for any help (as some of you might have
guessed i am a complete newbie )

Erik

Click to expand...

How do i know which compression to use to ensure i dont affect the original quality but still save some space?

Dikim said:

When i open a JPEG from my camera the file is approx 2Mb, but when
i then save it from Adobe Photoshop CS with maximum compression the
file gets up to mayby 6 Mb. Why?

Is there a way to get Photoshop to choose the same quality as i
opened the JPEG in?

I would be very thankful for any help (as some of you might have
guessed i am a complete newbie )

Click to expand...

I think you may not accurately be describing your situation. Did you really mean to say that the opened jpeg (i.e., un_compressed) is approx 2 MB, or is that just the compressed filesize that's saved by the camera? If you open a jpeg file in Photoshop and its ( un_compressed) filesize is only 2 MB, then it will not become a 6 MB file when saved by Photoshop using "maximum compression". I wonder if perhaps you saved at "quality level 12", which is not maximum compression, but rather is maximum quality (i.e., it's minimum compression!) Maximum compression is level 1.

Phil

I am sorry, but i dont really know how to describe it.

My 5 megapixel camera saves jpeg files that are 2 megabytes.

When i open them in Photoshop, do auto-levels and then pick "Save As..." and choose jpeg compression 12 (maximum) the new file is 6 megabytes.

What i would like is that photoshop didn't alter the jpeg compression, just added my levels and then used the same compression to save the new file.

I am afraid that by choosing a lower quality i will loose data, but it seems strange that the new file is 3x the original from the camera.

If i interpret your answer correctly are you saying that PS un-compresses the file (kind of makes it into a TIFF?) when i work with it?

Phil Rose said:

I think you may not accurately be describing your situation. Did
you really mean to say that the opened jpeg (i.e., un_compressed)
is approx 2 MB, or is that just the compressed filesize that's
saved by the camera? If you open a jpeg file in Photoshop and its
( un_compressed) filesize is only 2 MB, then it will not become a
6 MB file when saved by Photoshop using "maximum compression". I
wonder if perhaps you saved at "quality level 12", which is not
maximum compression, but rather is maximum quality (i.e., it's
minimum compression!) Maximum compression is level 1.

Phil

Click to expand...

I think you are still confused. When you choose the numbers 1-12 when saving in photoshop, it is describing quality, NOT compression. 12 is maximum quality, 1 is minimum quality, I usually save at around 8.

Dikim said:

My 5 megapixel camera saves jpeg files that are 2 megabytes.
When i open them in Photoshop, do auto-levels and then pick "Save
As..." and choose jpeg compression 12 (maximum) the new file is 6
megabytes.

What i would like is that photoshop didn't alter the jpeg
compression, just added my levels and then used the same
compression to save the new file.

I am afraid that by choosing a lower quality i will loose data, but
it seems strange that the new file is 3x the original from the
camera.

If i interpret your answer correctly are you saying that PS
un-compresses the file (kind of makes it into a TIFF?) when i work
with it?

Dikim said:

I think you may not accurately be describing your situation. Did
you really mean to say that the opened jpeg (i.e., un_compressed)
is approx 2 MB, or is that just the compressed filesize that's
saved by the camera? If you open a jpeg file in Photoshop and its
( un_compressed) filesize is only 2 MB, then it will not become a
6 MB file when saved by Photoshop using "maximum compression". I
wonder if perhaps you saved at "quality level 12", which is not
maximum compression, but rather is maximum quality (i.e., it's
minimum compression!) Maximum compression is level 1.

Phil

Click to expand...

Click to expand...

Dikim said:

When i open a JPEG from my camera the file is approx 2Mb, but when
i then save it from Adobe Photoshop CS with maximum compression the
file gets up to mayby 6 Mb. Why?

Is there a way to get Photoshop to choose the same quality as i
opened the JPEG in?

I would be very thankful for any help (as some of you might have
guessed i am a complete newbie )

Erik

Click to expand...

Dikim, you should NOT be saving your files as JPG's at all, unless you have finished working on them and want to send them on the internet. Every time you save as a JPG, the file is further compressed; i.e. some more of the original informatin is lost. You should save your files as either TIFF's or PSD's as you work on them. Then when you are done, you can save two versions, if you want to also have the files in the form of a JPG. But you should always retain an original, un-altered, un-worked-on version in a place (such as a CD) where it cannot be altered by mistake. This is done by making a copy, rather than just "saving" it.
--
KathyN

Ok thanks, that explains a lot.

i am sorry if i seemed comfused, because i was

KathyN said:

Dikim, you should NOT be saving your files as JPG's at all, unless
you have finished working on them and want to send them on the
internet. Every time you save as a JPG, the file is further
compressed; i.e. some more of the original informatin is lost. You
should save your files as either TIFF's or PSD's as you work on
them. Then when you are done, you can save two versions, if you
want to also have the files in the form of a JPG. But you should
always retain an original, un-altered, un-worked-on version in a
place (such as a CD) where it cannot be altered by mistake. This is
done by making a copy, rather than just "saving" it.
--
KathyN

Click to expand...

Basic rule,NEVER use the "save" command,use "save as" and add a suffix to the number,this means you never overwrite your original.look after your original as if it was a film negative.

KathyN said:

Dikim said:

When i open a JPEG from my camera the file is approx 2Mb, but when
i then save it from Adobe Photoshop CS with maximum compression the
file gets up to mayby 6 Mb. Why?

Is there a way to get Photoshop to choose the same quality as i
opened the JPEG in?

I would be very thankful for any help (as some of you might have
guessed i am a complete newbie )

Erik

Click to expand...

Dikim, you should NOT be saving your files as JPG's at all, unless
you have finished working on them and want to send them on the
internet. Every time you save as a JPG, the file is further
compressed; i.e. some more of the original informatin is lost. You
should save your files as either TIFF's or PSD's as you work on
them. Then when you are done, you can save two versions, if you
want to also have the files in the form of a JPG. But you should
always retain an original, un-altered, un-worked-on version in a
place (such as a CD) where it cannot be altered by mistake. This is
done by making a copy, rather than just "saving" it.
--
KathyN

Click to expand...

--
Frank Perry

Dikim said:

I am sorry, but i dont really know how to describe it.

My 5 megapixel camera saves jpeg files that are 2 megabytes.
When i open them in Photoshop, do auto-levels and then pick "Save
As..." and choose jpeg compression 12 (maximum) the new file is 6
megabytes.

What i would like is that photoshop didn't alter the jpeg
compression, just added my levels and then used the same
compression to save the new file.

I am afraid that by choosing a lower quality i will loose data, but
it seems strange that the new file is 3x the original from the
camera.

Click to expand...

All that means is that Photoshop's highest-quality JPG compression is higher-quality than your camera's. If you're under the impression that your camera is able to somehow save a 2MB file at the same quality as what Photoshop requires 6MB to do, that is not the case. If you want to save 2MB jpgs, adjust the quality slider in Photoshop down until you end up with a 2MB file (probably around 10).

--
Jeff Kohn
Houston, TX
http://www.pbase.com/jkohn