Saving edited pictures

I am editing pictures with Nikon Edit preparatory to having them
printed. The originals are 2272 x 1704 (full size) and saved at the
Fine setting 1:4 Jpg compression. After editing, they can be saved at
five levels of compressions (names not amount of compression is
given). Saving at the highest level (I believe it is 1:4) results in
a file of 4 megs or more and saving at the next level ( Probably 1:8
compression) results in a file of 1.3-1.7 megs evem with very little
editing such as changing just the density or the contrast.

My first question is, why does the file get so much bigger? if the
original 1:4 compression results in a 1.1 meg file I would think after
editing that another 1:4 compression would result in an even smaller
file instead of a huge file.

My second question how much degredation can I expect if I save edited
files at at 1:8 compression?.

On Tue, 26 Oct 2004 01:16:11 GMT, "George E. Cawthon"
wrote:

I am editing pictures with Nikon Edit preparatory to having them
printed. The originals are 2272 x 1704 (full size) and saved at the
Fine setting 1:4 Jpg compression. After editing, they can be saved at
five levels of compressions (names not amount of compression is
given). Saving at the highest level (I believe it is 1:4) results in
a file of 4 megs or more and saving at the next level ( Probably 1:8
compression) results in a file of 1.3-1.7 megs evem with very little
editing such as changing just the density or the contrast.

My first question is, why does the file get so much bigger? if the
original 1:4 compression results in a 1.1 meg file I would think after
editing that another 1:4 compression would result in an even smaller
file instead of a huge file.

My second question how much degredation can I expect if I save edited
files at at 1:8 compression?.
Image editors generally operate by decompressing the JPEG file into
memory. You then edit the uncompressed file in memory. When the file
is saved, it is resampled to produce a new JPEG file. The size of the
outgoing file is a function mainly of the "quality" setting and is not
related to the size or JPEG quality of the incoming file.

If you are at all serious about digital photography, I recommend you
invest in an image editting program that can save in a "lossless"
format. Each time you edit and save a JPEG file, you will suffer some
loss in quality. Here are some guidelines:

1. Keep a copy of the original JPEG file that comes from your camera.
Don't make any changes to this file. That way, you can always get back
to the original image if things get really messed up.
2. Save a working copy of your image in a lossless format. Use the
"native" format of your image editor (PSD for Photoshop) or a lossless
format like TIFF. These files are bigger than JPEG files, but you can
edit and save them repeatedly without loss of quality. Keep your
working copy around. Even when you think you are through with an
image, you may print it and find that you want to tweak it a bit more.
3. You can, of course, save the editted files as new JPEGs, but if you
need to do additional editting, go back to your lossless format
working copy.

For image editing, Photoshop is quite good, but it is expensive.
Paintshop Pro is pretty good and not nearly as expensive as Photoshop.
There are third-party books available for both.

Cheers,

Leonard

On Tue, 26 Oct 2004 01:16:11 GMT, "George E. Cawthon"
wrote:

I am editing pictures with Nikon Edit preparatory to having them
printed. The originals are 2272 x 1704 (full size) and saved at the
Fine setting 1:4 Jpg compression. After editing, they can be saved at
five levels of compressions (names not amount of compression is
given). Saving at the highest level (I believe it is 1:4) results in
a file of 4 megs or more and saving at the next level ( Probably 1:8
compression) results in a file of 1.3-1.7 megs evem with very little
editing such as changing just the density or the contrast.

My first question is, why does the file get so much bigger? if the
original 1:4 compression results in a 1.1 meg file I would think after
editing that another 1:4 compression would result in an even smaller
file instead of a huge file.

My second question how much degredation can I expect if I save edited
files at at 1:8 compression?.
Image editors generally operate by decompressing the JPEG file into
memory. You then edit the uncompressed file in memory. When the file
is saved, it is resampled to produce a new JPEG file. The size of the
outgoing file is a function mainly of the "quality" setting and is not
related to the size or JPEG quality of the incoming file.

If you are at all serious about digital photography, I recommend you
invest in an image editting program that can save in a "lossless"
format. Each time you edit and save a JPEG file, you will suffer some
loss in quality. Here are some guidelines:

1. Keep a copy of the original JPEG file that comes from your camera.
Don't make any changes to this file. That way, you can always get back
to the original image if things get really messed up.
2. Save a working copy of your image in a lossless format. Use the
"native" format of your image editor (PSD for Photoshop) or a lossless
format like TIFF. These files are bigger than JPEG files, but you can
edit and save them repeatedly without loss of quality. Keep your
working copy around. Even when you think you are through with an
image, you may print it and find that you want to tweak it a bit more.
3. You can, of course, save the editted files as new JPEGs, but if you
need to do additional editting, go back to your lossless format
working copy.

For image editing, Photoshop is quite good, but it is expensive.
Paintshop Pro is pretty good and not nearly as expensive as Photoshop.
There are third-party books available for both.

Cheers,

Leonard