Am I hurting my JPEG's?

I've read that it's bad to work from the original jpeg in photoshop because it can be harmed. I edit from my originals and do a "save as" with a different name in a different directory. Is my way harmful?

Charlie

if you save a jpg over and over again after modifications you degrade
image quality ... you should backup the original jpg and store modified
versions as tiff ... whenver the contents of a 8x8 pixel area is modified
this area will be recompressed ... over time and many saves you reduce
quality ...

I shoot RAW... convert to 16bit edit in 16bit and convert to 8bit
before I USM and print when I want maximum quality ... not
all the time though only for my commercial stuff ... not for portraits
etc ..

have fun
gmd

Charlie Schumacher said:

I've read that it's bad to work from the original jpeg in photoshop
because it can be harmed. I edit from my originals and do a "save
as" with a different name in a different directory. Is my way
harmful?

Charlie

Click to expand...

--
More time would make me even happier.

wing88 said:

if you save a jpg over and over again after modifications you degrade
image quality ... you should backup the original jpg and store
modified
versions as tiff ... whenver the contents of a 8x8 pixel area is
modified
this area will be recompressed ... over time and many saves you reduce
quality ...

I shoot RAW... convert to 16bit edit in 16bit and convert to 8bit
before I USM and print when I want maximum quality ... not
all the time though only for my commercial stuff ... not for portraits
etc ..

have fun
gmd

Click to expand...

wing88 said:

Charlie Schumacher said:

I've read that it's bad to work from the original jpeg in photoshop
because it can be harmed. I edit from my originals and do a "save
as" with a different name in a different directory. Is my way
harmful?

Charlie

Click to expand...

--
More time would make me even happier.

Click to expand...

Hi

That piece of advice will help me I always edit original and "save as" Thanks, from now on i will duplicate image.

As long as you take care not to blow away the original! So I'd recommend making a copy before editing.

What is problematic is saving your intermediate work using jpeg compression. Each time you do this, you lose image quality in the new version, because the compression/decompression process is unable to exactly reproduce the contents of the previous version (this is why jpeg is known as a "lossy" format). Also, jpeg has a way of inducing certain "artifacts" into the image, especially under higher compression ratios. So if you make a habit of using jpeg within your workflow, you will potentially "harm" your image. And if you use moderate to high compression ratios, you risk introducing significant artifacting, harming the image even further.

I shoot to jpeg, because my camera generates good results, and uses very low compression to achieve high quality. So I can get a few hundred images onto a microdrive, which is important for the kind of shooting I often do. However, I have a RULE, which I recommend you consider adopting:

"When an image enters my workflow, it immediately goes into TIFF format."

TIFF (when uncompressed, and using certain compression types, such as LZW) is known as a non-lossy format - i.e. the act of saving a new version does not lose information. What you get when you read a TIFF into your editor is exactly what you had on your screen when you saved it. The only time I produce a jpeg once an image is in my workflow is when it exits the workflow - i.e. when I create whatever end output is required for the medium I'm dealing with - printer, web page, VCD, etc...

Charlie Schumacher said:

I've read that it's bad to work from the original jpeg in photoshop
because it can be harmed. I edit from my originals and do a "save
as" with a different name in a different directory. Is my way
harmful?

Charlie

Click to expand...

I used to convert everything to TIFF, but I decided that it costs more than it tastes as I was converting hundreds and thousands of files. Besides... TIFFs are big!
Now I am having mostly Highest quality jpegs to work with.

The important thing is never to write over any of the original images with a edited version. That way, when I decide which ones of the thousands of photos are the keepers, I can tap back to the origianls, and convert those 2.

This works for me, as great majority of my shots will only be seen by me on my screen, as I browse through them, thinking 'I should go back there some day and take a better shot on this' )

Its ONLY COMMON SENSE and good practice to work on a copy and keep a back up of the original

Charlie Schumacher150057 said:

What is problematic is saving your intermediate work using jpeg
compression. Each time you do this, you lose image quality in the new
version,

Click to expand...

I've seen this posted OVER AND OVER AND OVER, and while its technically true. I've NEVER seen anyone actually QUALIFY the EXTENT of the LOSS of image QUALITY.

Its certainly true of LOW LEVEL jpeg compression, and one can see this as you move the quality slider to the lower level (if your program has live preview) you can see the jpeg artifacts slowly grow larger and more pronounced.

BUT...

...for HIGH LEVEL jpeg compression, as graphics programs have become more sophisticated, working in and saving digital files in the HIGHEST level jpeg compression means the loss of image quality is (IMHO) SO SMALL it literally becomes unimportant

I don't work in RAW (yes my camera will shoot RAW), I ONLY use the highest quality jpeg, and I have NEVER had ANYONE look at my prints and say, OH DARN, I see you use jpeg, too bad you saved it too many times, it could have been a nice print.

The bottom line for me is, if the people looking at my prints DON'T SEE any loss of quality, can't tell I use jpeg from Tiff or RAW, and think my prints are spectacular, why should I worry if my jpeg saves loose's a pixel here or there, or changes the color of a couple pixels when no one can tell the difference

• Ivan

Chris 749 said:

wing88 said:

if you save a jpg over and over again after modifications you degrade
image quality ... you should backup the original jpg and store
modified
versions as tiff ... whenver the contents of a 8x8 pixel area is
modified
this area will be recompressed ... over time and many saves you reduce
quality ...

Click to expand...

Hi
That piece of advice will help me I always edit original and "save
as" Thanks, from now on i will duplicate image.

Click to expand...

Starting with a duplicate jpeg image is an unnecessary step (although it can't hurt) and will not help you--because what you describe is not degrading your original image at all. If, as you say, you edit and then only do a "Save as...", the original jpeg is untouched. Of course you must not do a Save before closing the original.

Phil

If you save in the highest quality, jpeg lossage is minimal enough that for many casual photographers, it is probably small enough that it is not noticeable.

But the lossage even in highest quality mode is clear even in a second generation copy. We're not just talking about jpeg artifacting, we're also talking about the colors in the image. Pixels will typically have subtle changes in value, and it becomes more pronounced the more generations saved. Minimally, you are introducing small changes in colors within the image.

And this is not limited to a couple of pixels here and there - it is a pervasive effect throughout the image.

If you don't believe me, try it. Here's an example:

Take the following three images:

Generation 1, highest quality:



Generation 2, highest quality:



Generation 10, highest quality:



They are all the same, right? NOT! To exemplify, in my editor, pixel 39,108 has the following RGB values:

Image generation 1: R 139 G 77 B 64
Image generation 2: R 137 G 78 B 60
Image generation 10: R 135 G 79 B 62

Now that was with highest quality. At 50% compression factor, that same pixel in a 2nd generation image comes in at R 133 G 87 B 64:

Generation 2, 50% compression factor:



Compare other pixels in these images and you will see similar differences throughout. I will agree that the changes are often difficult to see - but they do exist. And they make it very clear that even in a 2nd generation jpeg at highest quality, that I am dealing with a different set of pixels than I started with.

Taking it further - the compression/decompression in one tool may generate different results than in another. I did the above with PSP 7.04. If you checked the pixel values with PS, I would bet that you'll get different values - for example in PS Elements 2.0, the same pixel for the 2nd generation highest quality jpeg shows up as: R 140 G 77 B 62. With TIFF, the pixel values will be the same across tools.

Ivan Good said:

Ivan Good said:

What is problematic is saving your intermediate work using jpeg
compression. Each time you do this, you lose image quality in the new
version,

Click to expand...

I've seen this posted OVER AND OVER AND OVER, and while its
technically true. I've NEVER seen anyone actually QUALIFY the
EXTENT of the LOSS of image QUALITY.

Its certainly true of LOW LEVEL jpeg compression, and one can see
this as you move the quality slider to the lower level (if your
program has live preview) you can see the jpeg artifacts slowly
grow larger and more pronounced.

BUT...

...for HIGH LEVEL jpeg compression, as graphics programs have
become more sophisticated, working in and saving digital files in
the HIGHEST level jpeg compression means the loss of image quality
is (IMHO) SO SMALL it literally becomes unimportant

I don't work in RAW (yes my camera will shoot RAW), I ONLY use the
highest quality jpeg, and I have NEVER had ANYONE look at my prints
and say, OH DARN, I see you use jpeg, too bad you saved it too many
times, it could have been a nice print.

The bottom line for me is, if the people looking at my prints DON'T
SEE any loss of quality, can't tell I use jpeg from Tiff or RAW,
and think my prints are spectacular, why should I worry if my jpeg
saves loose's a pixel here or there, or changes the color of a
couple pixels when no one can tell the difference

• Ivan

Click to expand...

It is always a best practice to copy the original (i.e. copy the file itself, not save a new version in your editor). I learned my lesson on that one long ago and haven't made the same mistake since.

Phil Rose said:

Chris 749 said:

wing88 said:

if you save a jpg over and over again after modifications you degrade
image quality ... you should backup the original jpg and store
modified
versions as tiff ... whenver the contents of a 8x8 pixel area is
modified
this area will be recompressed ... over time and many saves you reduce
quality ...

Click to expand...

Hi
That piece of advice will help me I always edit original and "save
as" Thanks, from now on i will duplicate image.

Click to expand...

Starting with a duplicate jpeg image is an unnecessary step
(although it can't hurt) and will not help you--because what you
describe is not degrading your original image at all. If, as you
say, you edit and then only do a "Save as...", the original jpeg is
untouched. Of course you must not do a Save before closing the
original.

Phil

Click to expand...

In my experience the jpeg degradation issue is a significent one. I now shoot in jpeg, then work on the copy as a PSD file, only carrying out USM and jpeg conversion at the final stage.

But I do shoot a lot in low-light conditions at fast shutterspeeds. Just opening, saving, opening, saving, at photoshop JPEG =12 probably doesnt cause a problem, but if you want to tweek colours, levels, etc. I find there can be a problem.

lol .. this is just naive what you said )
if it works for you ... be happy

have fun
gmd

Ivan Good said:

Ivan Good said:

What is problematic is saving your intermediate work using jpeg
compression. Each time you do this, you lose image quality in the new
version,

Click to expand...

I've seen this posted OVER AND OVER AND OVER, and while its
technically true. I've NEVER seen anyone actually QUALIFY the
EXTENT of the LOSS of image QUALITY.

Its certainly true of LOW LEVEL jpeg compression, and one can see
this as you move the quality slider to the lower level (if your
program has live preview) you can see the jpeg artifacts slowly
grow larger and more pronounced.

BUT...

...for HIGH LEVEL jpeg compression, as graphics programs have
become more sophisticated, working in and saving digital files in
the HIGHEST level jpeg compression means the loss of image quality
is (IMHO) SO SMALL it literally becomes unimportant

I don't work in RAW (yes my camera will shoot RAW), I ONLY use the
highest quality jpeg, and I have NEVER had ANYONE look at my prints
and say, OH DARN, I see you use jpeg, too bad you saved it too many
times, it could have been a nice print.

The bottom line for me is, if the people looking at my prints DON'T
SEE any loss of quality, can't tell I use jpeg from Tiff or RAW,
and think my prints are spectacular, why should I worry if my jpeg
saves loose's a pixel here or there, or changes the color of a
couple pixels when no one can tell the difference

• Ivan

Click to expand...

--
More time would make me even happier.