Saving an image in .jpg

Say I took two identical 4MP pictures, one at lowest .jpg compression and the other at highest .jpg compression.
Then I perform the same operation on each one (say a level adjustment). Then I choose to "SAVE AS" a .jpg.
At this point, PS asks me what compression level do I want to use on the saved images. That is fine and reasonable.
However, if I choose to "SAVE" them, PS just saves them without asking me what amount of compression I want to use.
How does it know at which compression level to save each image. Does it SAVE the highly compressed image at at a high compression and the lowly compressed one at a low compression?
Does it try to maintain approximately the original file size for each image?.......What?
Bob Williams

In article ,
Bob Williams wrote:

Say I took two identical 4MP pictures, one at lowest .jpg compression and the other at highest .jpg compression.
Then I perform the same operation on each one (say a level adjustment). Then I choose to "SAVE AS" a .jpg.

You should avoid doing this. JPEG is "lossy" compression. It works by degrading the quality of the image. This degradation is cumulative; that means, if you save a JPEG, you lose image quality. Then if you open it and save it again, you lose more quality. Open it and save it again, you lose still more quality. This degradation is irreversible; do it enough times and the image turns to mush.

At this point, PS asks me what compression level do I want to use on the saved images. That is fine and reasonable.
However, if I choose to "SAVE" them, PS just saves them without asking me what amount of compression I want to use.
How does it know at which compression level to save each image.

If the image was saved by Photoshop to begin with:

Photoshop stores special information in the image that records the JPEG settings, and uses the same settings.

If the image was not saved by Photoshop to begin with:

Photoshop uses whatever settings you used last time you did "Save As" with some other image.

Does it SAVE the highly compressed image at at a high compression and the lowly compressed one at a low compression?

If the images were originally saved in Photoshop, yes. If not, no.

--
Art, photography, shareware, polyamory, literature, kink: all at http://www.xeromag.com/franklin.html

If you want to keep your image quality intact, by all means save it as a ..tif. If you need it in another format, you can always duplicate it and save it in whatever format you want.

Be mindful of disk space, though. You may want to back it up on a CD or something to save hard drive/network space.

Skywolf.
"Tacit" wrote in message

In article ,
Bob Williams wrote:

Say I took two identical 4MP pictures, one at lowest .jpg compression and the other at highest .jpg compression.
Then I perform the same operation on each one (say a level adjustment). Then I choose to "SAVE AS" a .jpg.

You should avoid doing this. JPEG is "lossy" compression. It works by degrading the quality of the image. This degradation is cumulative; that means, if you save a JPEG, you lose image quality. Then if you open it and save it again, you lose more quality. Open it and save it again, you lose still more quality. This degradation is irreversible; do it enough times and the image turns to mush.

At this point, PS asks me what compression level do I want to use on the saved images. That is fine and reasonable.
However, if I choose to "SAVE" them, PS just saves them without asking me what amount of compression I want to use.
How does it know at which compression level to save each image.

If the image was saved by Photoshop to begin with:

Photoshop stores special information in the image that records the JPEG settings, and uses the same settings.

If the image was not saved by Photoshop to begin with:

Photoshop uses whatever settings you used last time you did "Save As" with some other image.

Does it SAVE the highly compressed image at at a high compression and the lowly compressed one at a low compression?

If the images were originally saved in Photoshop, yes. If not, no.
--
Art, photography, shareware, polyamory, literature, kink: all at http://www.xeromag.com/franklin.html

Tacit wrote:

In article ,
Bob Williams wrote:

Say I took two identical 4MP pictures, one at lowest .jpg compression and the other at highest .jpg compression.
Then I perform the same operation on each one (say a level adjustment). Then I choose to "SAVE AS" a .jpg.

You should avoid doing this. JPEG is "lossy" compression. It works by degrading the quality of the image. This degradation is cumulative; that means, if you save a JPEG, you lose image quality. Then if you open it and save it again, you lose more quality. Open it and save it again, you lose still more quality. This degradation is irreversible; do it enough times and the image turns to mush.

At this point, PS asks me what compression level do I want to use on the saved images. That is fine and reasonable.
However, if I choose to "SAVE" them, PS just saves them without asking me what amount of compression I want to use.
How does it know at which compression level to save each image.

If the image was saved by Photoshop to begin with:

Photoshop stores special information in the image that records the JPEG settings, and uses the same settings.

If the image was not saved by Photoshop to begin with:

Photoshop uses whatever settings you used last time you did "Save As" with some other image.

********************************************

WOW! That's really spooky.
Consider this hypothetical case:
1.)Suppose yesterday I sent an e-mail image, SAVED AS a jpg and compressed strongly, (let's say to level 3), to reduce my recipient's download time.
2.)Then, today I download some images from my camera, which were captured in superfine quality jpeg, to a desktop folder.
3.)I crop each image to a 4:6 aspect ratio and SAVE them back to the folder.
(I do this because I will eventually burn all the cropped images in the folder to a CD, to bring to WalMart for printing)
Are you saying that all my "SAVES" will be at level 3 compression because that was the level of my last "SAVE AS" yesterday? Bob Williams

********************************

Does it SAVE the highly compressed image at at a high compression and the lowly compressed one at a low compression?

If the images were originally saved in Photoshop, yes. If not, no.

"Bob Williams" wrote in message

Tacit wrote:

In article ,
Bob Williams wrote:

Say I took two identical 4MP pictures, one at lowest .jpg compression and the other at highest .jpg compression.
Then I perform the same operation on each one (say a level adjustment). Then I choose to "SAVE AS" a .jpg.

You should avoid doing this. JPEG is "lossy" compression. It works by degrading the quality of the image. This degradation is cumulative; that means, if you save a JPEG, you lose image quality. Then if you open it and save it again, you lose more quality. Open it and save it again, you lose still more quality. This degradation is irreversible; do it enough times and the image turns to mush.

At this point, PS asks me what compression level do I want to use on the saved images. That is fine and reasonable.
However, if I choose to "SAVE" them, PS just saves them without asking me what amount of compression I want to use.
How does it know at which compression level to save each image.

If the image was saved by Photoshop to begin with:

Photoshop stores special information in the image that records the JPEG settings, and uses the same settings.

If the image was not saved by Photoshop to begin with:

Photoshop uses whatever settings you used last time you did "Save As" with some other image.

********************************************

WOW! That's really spooky.
Consider this hypothetical case:
1.)Suppose yesterday I sent an e-mail image, SAVED AS a jpg and compressed strongly, (let's say to level 3), to reduce my recipient's download time.
2.)Then, today I download some images from my camera, which were captured
in superfine quality jpeg, to a desktop folder.
3.)I crop each image to a 4:6 aspect ratio and SAVE them back to the folder.
(I do this because I will eventually burn all the cropped images in the folder to a CD, to bring to WalMart for printing)
Are you saying that all my "SAVES" will be at level 3 compression because that was the level of my last "SAVE AS" yesterday? Bob Williams

********************************

Does it SAVE the highly compressed image at at a high compression and the lowly compressed one at a low compression?

If the images were originally saved in Photoshop, yes. If not, no.

Yes it will.

That is one of the reasons, people who care about image quality do not use Jpeg as their "regular" file type.

I save in Photoshop's own PSD, and use that as my File Type for everything. There is no quality loss with PSD.

They do take up more space on the HDD and Cds, but storage space is cheap.

When I need to send one by Email or post onto the Web, it is easy to convert using "Save for Web", but even then I work on a copy of the PSD, just in case I forget what I am doing and allow Ps to "Save the changes" when I close the Image.

Roy G

"Bob Williams" wrote

3.)I crop each image to a 4:6 aspect ratio and SAVE them back to the folder.
(I do this because I will eventually burn all the cropped images in the folder to a CD, to bring to WalMart for printing)

JPEG throws away detail, but what do you care if your printer is Walmart? Come on, let's get realistic here.

Bob Williams wrote:

WOW! That's really spooky.
Consider this hypothetical case:
1.)Suppose yesterday I sent an e-mail image, SAVED AS a jpg and compressed strongly, (let's say to level 3), to reduce my recipient's download time.
2.)Then, today I download some images from my camera, which were captured in superfine quality jpeg, to a desktop folder.
3.)I crop each image to a 4:6 aspect ratio and SAVE them back to the
folder.
(I do this because I will eventually burn all the cropped images in the folder to a CD, to bring to WalMart for printing)
Are you saying that all my "SAVES" will be at level 3 compression because that was the level of my last "SAVE AS" yesterday?

I don't think he's saying that, as it's wrong. The Save As memory applies only to each individual re-save.

Fears about losses with resaving in a low compression jpeg format are frequently hysterical.

--
John McWilliams

Even if you learned to speak English perfectly, whom would you speak it to?

In article
wrote:

1.)Suppose yesterday I sent an e-mail image, SAVED AS a jpg and compressed strongly, (let's say to level 3), to reduce my recipient's download time.
2.)Then, today I download some images from my camera, which were captured in superfine quality jpeg, to a desktop folder.
3.)I crop each image to a 4:6 aspect ratio and SAVE them back to the folder.
(I do this because I will eventually burn all the cropped images in the folder to a CD, to bring to WalMart for printing)
Are you saying that all my "SAVES" will be at level 3 compression because that was the level of my last "SAVE AS" yesterday?

Yes. That's exactly right.

There are two important considerations with JPEG files:

1. Never continually re-save files in JPEG format. It causes cumulative degradation. If you want to adjust some images from your digital camera, save them as TIFF, not JPEG, when you are done, and archive the TIFFs. Use the TIFFs to create JPEGs if you must have a JPEG for a specific purpose, such as emailing or posting on the Web.

2. Do not just hit Control-S to save a JPEG if it didn't come from Photoshop.

--
Art, photography, shareware, polyamory, literature, kink: all at http://www.xeromag.com/franklin.html

In article ,
John McWilliams wrote:

I don't think he's saying that, as it's wrong. The Save As memory applies only to each individual re-save.

No, thats exactly what I'm saying. Photoshop has absolutely, positively no way to know the JPEG parameters of a JPEG it did not create--so it uses whatever parameters it used last when you save, say, a JPEG from a digital camera.

Fears about losses with resaving in a low compression jpeg format are frequently hysterical.

There are many people who claim that if you re-save a JPEG with a high quality setting, you "can't tell," or that the degradation is "not noticeable." For some people, that's probably true; some people probably can't tell. I can, and many people can, and any image that you care about should not be subject to unnecessary degradation.

--
Art, photography, shareware, polyamory, literature, kink: all at http://www.xeromag.com/franklin.html

a wonderful feature in WIN XP is click on any jpg image file and choose> send to mail recipient> it will auto resize a copy and put it into an email header so you don't have to waste time re-sizing a lot of images just to share in email.

I would not suggest resizing your original jpgs use (save as) choose a lossless format like tiff or psd. For remaking the adjusted image for use on internet use "SAVE FOR WEB" , choose jpg high, save.(not over your original, rename it).

If you are only planning to print 4x6 and are sure you will never need these images for anything else but Wal-Mart prints why shoot superfine in the first place? Keep in mind today's crappy snapshot just may be the only pic of a deceased friend or a record of some important event in a few years time. My own daughter used to throw out the negatives after she received her 4x6's thinking it was trash you never need again.

"Roy" wrote in message

"Bob Williams" wrote in message

Tacit wrote:

In article ,
Bob Williams wrote:

Say I took two identical 4MP pictures, one at lowest .jpg compression and the other at highest .jpg compression.
Then I perform the same operation on each one (say a level adjustment). Then I choose to "SAVE AS" a .jpg.

You should avoid doing this. JPEG is "lossy" compression. It works by degrading the quality of the image. This degradation is cumulative; that means, if you save a JPEG, you lose image quality. Then if you open it and save it again, you lose more quality. Open it and save it again, you lose still more quality. This degradation is irreversible; do it enough times and the image turns to mush.

At this point, PS asks me what compression level do I want to use on the saved images. That is fine and reasonable.
However, if I choose to "SAVE" them, PS just saves them without asking me what amount of compression I want to use.
How does it know at which compression level to save each image.

If the image was saved by Photoshop to begin with:

Photoshop stores special information in the image that records the JPEG settings, and uses the same settings.

If the image was not saved by Photoshop to begin with:

Photoshop uses whatever settings you used last time you did "Save As" with some other image.

********************************************

WOW! That's really spooky.
Consider this hypothetical case:
1.)Suppose yesterday I sent an e-mail image, SAVED AS a jpg and compressed strongly, (let's say to level 3), to reduce my recipient's download time.
2.)Then, today I download some images from my camera, which were captured in superfine quality jpeg, to a desktop folder.
3.)I crop each image to a 4:6 aspect ratio and SAVE them back to the folder.
(I do this because I will eventually burn all the cropped images in the folder to a CD, to bring to WalMart for printing)
Are you saying that all my "SAVES" will be at level 3 compression because that was the level of my last "SAVE AS" yesterday? Bob Williams

********************************

Does it SAVE the highly compressed image at at a high compression and the lowly compressed one at a low compression?

If the images were originally saved in Photoshop, yes. If not, no.

Yes it will.

That is one of the reasons, people who care about image quality do not use Jpeg as their "regular" file type.

I save in Photoshop's own PSD, and use that as my File Type for everything. There is no quality loss with PSD.

They do take up more space on the HDD and Cds, but storage space is cheap.
When I need to send one by Email or post onto the Web, it is easy to convert using "Save for Web", but even then I work on a copy of the PSD, just in case I forget what I am doing and allow Ps to "Save the changes" when I close the Image.

Roy G

"KatWoman" wrote in message

a wonderful feature in WIN XP is click on any jpg image file and choose> send to mail recipient> it will auto resize a copy and put it into an email header so you don't have to waste time re-sizing a lot of images just to share in email.

Take it up a step and get the free Microsoft XP Power Tools. One of them adds a right-click feature to resize images, in mass or individually.

See the snapshot: http://elearning.winona.edu/jjs/click.gif

if you select a list of pictures with ctrl shift click it will change the lot of them for emailing

"johnboy" wrote in message

"KatWoman" wrote in message

a wonderful feature in WIN XP is click on any jpg image file and choose> send to mail recipient> it will auto resize a copy and put it into an email header so you don't have to waste time re-sizing a lot of images just to share in email.

Take it up a step and get the free Microsoft XP Power Tools. One of them adds a right-click feature to resize images, in mass or individually.
See the snapshot: http://elearning.winona.edu/jjs/click.gif

johnboy wrote:

"Bob Williams" wrote

3.)I crop each image to a 4:6 aspect ratio and SAVE them back to the folder.
(I do this because I will eventually burn all the cropped images in the folder to a CD, to bring to WalMart for printing)

JPEG throws away detail, but what do you care if your printer is Walmart? Come on, let's get realistic here.

As I stated up front, this is a HYPOTHETICAL case, just to make sure that I understood exactly what Tacit was saying. (I did.)
BUT
Unless you have used WalMart's ONLINE printing service, I would not be so quick to disparage the quality of their prints.
I often have them print 8 X 10s from 240 ppi image files. Sometimes I will resample to 300 ppi in PS. (Don't see much difference.) I have compared them to prints made on Epson an 2200 and a Canon Pixma iP4000. Guess What?
The WalMart prints look better, especially under high magnification. And why shouldn't they? I'm fairly certain that WalMart's printer must cost hundreds of times as much as the consumer inkjets. The Fuji Frontier processor and Fuji Crystal Archive paper is just about state of the art. Who do you think could make a better print at 5X the price? Bob Williams

Tacit wrote:

In article
wrote:

1.)Suppose yesterday I sent an e-mail image, SAVED AS a jpg and compressed strongly, (let's say to level 3), to reduce my recipient's download time.
2.)Then, today I download some images from my camera, which were captured in superfine quality jpeg, to a desktop folder.
3.)I crop each image to a 4:6 aspect ratio and SAVE them back to the folder.
(I do this because I will eventually burn all the cropped images in the folder to a CD, to bring to WalMart for printing)
Are you saying that all my "SAVES" will be at level 3 compression because that was the level of my last "SAVE AS" yesterday?

Yes. That's exactly right.

There are two important considerations with JPEG files:

1. Never continually re-save files in JPEG format. It causes cumulative degradation. If you want to adjust some images from your digital camera, save them as TIFF, not JPEG, when you are done, and archive the TIFFs. Use the TIFFs to create JPEGs if you must have a JPEG for a specific purpose, such as emailing or posting on the Web.

I never re-save a jpeg image more than 2-3 times, max.
And then, always with highest quality compression.
I fully understand the dangers of multiple jpeg saves, but I have found that almost any image can tolerate 2-3 highest quality compressions without showing any noticeable degradation
To be absolutely safe, I probably should save in .psd but I have developed the habit of saving in jpeg from the days when a 4GB H.D. was pretty impressive.
I typically archive my originals (Superfine jpeg from the camera) on an 80GB external USB-2 H.D. Then I create a "Working" folder on my desktop. I then "worry" the image in PS until I like it and then SAVE AS a highest quality jpeg in an appropriate folder, e.g. Flowers, Animals, People etc.
Whenever I accumulate about 6-700 MB on my external H.D. I'll burn it to a CD for redundancy. That way I can always retrieve the original if I accidentally screw up an image in my working folder or in its destination folder.
Thanks for your knowledgeable response.
I can always take your answers "to the bank".
Bob Williams

2. Do not just hit Control-S to save a JPEG if it didn't come from Photoshop.

On Sat, 28 May 2005 22:11:28 -0700, Bob Williams
wrote:

Who do you think could make a better print at 5X the price?

Just about any professional photo lab for a start.

--

Hecate - The Real One

Fashion: Buying things you don't need, with money
you don't have, to impress people you don't like...

Tacit wrote:

In article ,
John McWilliams wrote:

I don't think he's saying that, as it's wrong. The Save As memory applies only to each individual re-save.

No, thats exactly what I'm saying. Photoshop has absolutely, positively no way to know the JPEG parameters of a JPEG it did not create--so it uses whatever parameters it used last when you save, say, a JPEG from a digital camera.

It brings up a dialogue that puts in the last used level, yes, but one would have to be pretty dense to not notice that! There's no way that I know of to get around the dialogue.

What I was referring to above was the skipping of the dialogue per individual image file that had already been saved in PS. Then it will remember the last level and apply that automatically.

Fears about losses with resaving in a low compression jpeg format are frequently hysterical.

There are many people who claim that if you re-save a JPEG with a high quality setting, you "can't tell," or that the degradation is "not noticeable." For some people, that's probably true; some people probably can't tell. I can, and many people can, and any image that you care about should not be subject to unnecessary degradation.

I don't disagree with your statements, but mine still stands.

--
John McWilliams

Hecate wrote:

On Sat, 28 May 2005 22:11:28 -0700, Bob Williams
wrote:

Who do you think could make a better print at 5X the price?

Just about any professional photo lab for a start.

If we were talking about printing negatives, I'd agree with you 100%. Skilled technicians are expected to do a lot of Levels and Color adjustment.......BUT.......
What can a pro lab do with a digital image that WalMart cannot do, other than use some exotic printing paper?
I do all the technical work to get the image exactly like I want it. I just want the image printed. I don't want someone fooling around with my edited file.
Also, what would a "Pro Lab" charge for an 8x10? Bob Williams

On Sun, 29 May 2005 23:36:13 -0700, Bob Williams
wrote:

Hecate wrote:

On Sat, 28 May 2005 22:11:28 -0700, Bob Williams
wrote:

Who do you think could make a better print at 5X the price?

Just about any professional photo lab for a start.

If we were talking about printing negatives, I'd agree with you 100%. Skilled technicians are expected to do a lot of Levels and Color adjustment.......BUT.......
What can a pro lab do with a digital image that WalMart cannot do, other than use some exotic printing paper?

Well, let's start with use colour management.

I do all the technical work to get the image exactly like I want it. I just want the image printed. I don't want someone fooling around with my edited file.

Do you use colour management? If you are you're wasting your time sending it the cheap, exploitative and nasty route. If you're not, how do you expect to get good results from the work you've put into your images?

Also, what would a "Pro Lab" charge for an 8x10?

In the US, no idea. In the UK, it varies, but the lab I use for my processing would charge £2.24 for a 10x8. If you wanted custom printing you'd need to add £5.25 to that, so a maximum of £7.79.

--

Hecate - The Real One

Fashion: Buying things you don't need, with money
you don't have, to impress people you don't like...

Hecate wrote:

On Sun, 29 May 2005 23:36:13 -0700, Bob Williams
wrote:

Hecate wrote:

On Sat, 28 May 2005 22:11:28 -0700, Bob Williams
wrote:

Who do you think could make a better print at 5X the price?

Just about any professional photo lab for a start.

If we were talking about printing negatives, I'd agree with you 100%. Skilled technicians are expected to do a lot of Levels and Color adjustment.......BUT.......
What can a pro lab do with a digital image that WalMart cannot do, other than use some exotic printing paper?

Well, let's start with use colour management.

I do all the technical work to get the image exactly like I want it. I just want the image printed. I don't want someone fooling around with my edited file.

Do you use colour management? If you are you're wasting your time sending it the cheap, exploitative and nasty route. If you're not, how do you expect to get good results from the work you've put into your images?

Also, what would a "Pro Lab" charge for an 8x10?

In the US, no idea. In the UK, it varies, but the lab I use for my processing would charge £2.24 for a 10x8. If you wanted custom printing you'd need to add £5.25 to that, so a maximum of £7.79.

Since you live in the U.K., I assume you have never used WalMart Online's services.
Why do you assume that their print quality is not excellent. I have a lot of experience with online printers and I find that WalMart Online is equal to any of them and is cheaper than most. Bob Williams

"Bob Williams" wrote in message

Since you live in the U.K., I assume you have never used WalMart Online's services.
Why do you assume that their print quality is not excellent. I have a lot of experience with online printers and I find that WalMart Online is equal to any of them and is cheaper than most.

equal to other crummy services is a measure of nothing

On Mon, 30 May 2005 23:40:54 -0700, Bob Williams
wrote:

Since you live in the U.K., I assume you have never used WalMart Online's services.
Why do you assume that their print quality is not excellent.

Because we have their bastard child over here called Asda.

I have a lot of experience with online printers and I find that WalMart Online is equal to any of them and is cheaper than most.

Depends on your standards.

--

Hecate - The Real One

Fashion: Buying things you don't need, with money
you don't have, to impress people you don't like...

On Tue, 31 May 2005 07:39:07 -0500, "johnboy" wrote:

"Bob Williams" wrote in message

Since you live in the U.K., I assume you have never used WalMart Online's services.
Why do you assume that their print quality is not excellent. I have a lot of experience with online printers and I find that WalMart Online is equal to any of them and is cheaper than most.

equal to other crummy services is a measure of nothing

Precisely.

--

Hecate - The Real One

Fashion: Buying things you don't need, with money
you don't have, to impress people you don't like...