Saving Pictures in Tiff CMYK or RGB??

WStoreyII wrote:

> Hello,
>
> I have recently learned that jpgs corrupt files. So i opened psp6
> and went to convert all the files that i have in to Tiffs however it
> had an option for RGB format or CMYK format. My questions is which
> one do i use, my printer (Epson Stylus Cx5400)uses cmyk color
> cartridges so i was thinking that is what i should use and that i
> could convert them to rgb if i need to use them for the web or
> anything.
>
> Please tell me if this is the right assumption and if not what to do.

Save yourself some work. Stick with RGB, since your printer driver takes
RGB input anyway.

And save yourself some work and stick with your jpgs for that matter. Jpegs
will indeed lose quality, but only each time you re-save in jpeg format.

Treat your original jpeg from the camera as if it were a negative, save your
edited image to another file, and avoid compressing the image more than one
additional time. If you plan to edit the same image again, save in an
umcompressed format such as tiff or psd.

Above all, try these things out for yourself and see if you can see the
difference - trust your eyes over anything you read here, including anything
I say :-)
--

Mike Russell
www.curvemeister.com
www.geigy.2y.net

Everything you are trying to do is incorrect.

1. Where did you learn that jpg corrupts files? Nonsense.

2. Your camera is sRGB, your video display is sRGB. All printers are CMYK.
There is no sense in saving a picture in CMYK. XP (or any photo software)
sends your sRGB file to your printer, it is translated automatically to what
your printer can understand.

If you converted to .tif you will see that these files will be about 10
times the size of .jpg.

The only time you want to save in .tif is when you want to edit the file
many times and "save as" many times.

We used .tif in the old days because resolution was poor and "save as" jpg
many times would degrade the image. These days are gone with cameras of 2 MP
and above.

If you want to convert the .tif files back to jpg you can use this free
batch converter:
http://www.irfanview.com/

Here is a way to do your own experiment.


This used to be correct, in the days of poor resolution digital cameras and
scanners. Things have changed dramatically and unless you want to print very
large (by large I mean more than 12 x 18) from a pro shop there is
absolutely no advantage to save tif files over jpg.

The first point is, every time you "Save as" a jpg there is a little loss
and artifacts introduced, so if you edit a picture and you Save as many
time, there is some degradation with each Save as, but not with Save if you
use Save to save your changes as you are editing(even if you don't do
anything to the picture and you Save as just to change the name of the file,
it is the Save as that is the problem). So if you plan to edit the file many
times, keep it in tif until done and then save it as jpg. Since you can
always saved it back as tif for further editing, no problem.
The second point is, can you see the difference? Only you can tell, no
amount of info will convince you. So you do the experiment yourself. It has
been done many times. Here is how to do it.
Take one of your jpg file, right click on it and click on Copy. Hold the
Ctrl key down and press the letter V. This will make a new file in your
folder "Copy of filename.jpg (note there is no degradation when you do this,
since you don't open the file and Save as, you only copied it). Now.
1. Open this file in your photo editor and Save as. Give it the name Copy of
filename 1.jpg
2. Open Copy of filename 1.jpg, Save as and change 1 to 2.
3. Continue doing this until you Save as this file 15 times.
The first point is, every time you "Save as" a jpg there is a little loss
and artifacts introduced, so if you edit a picture and you Save as many
time, there is some degradation with each Save as, but not with Save if you
use Save to save your changes as you are editing(even if you don't do
anything to the picture and you Save as just to change the name of the file,
it is the Save as that is the problem). So if you plan to edit the file many
times, keep it in tif until done and then save it as jpg. Since you can
always saved it back as tif for further editing, no problem.
The second point is, can you see the difference? Only you can tell, no
amount of info will convince you. So you do the experiment yourself. It has
been done many times. Here is how to do it.
Take one of your jpg file, right click on it and click on Copy. Hold the
Ctrl key down and press the letter V. This will make a new file in your
folder "Copy of filename.jpg (note there is no degradation when you do this,
since you don't open the file and Save as, you only copied it). Now.
1. Open this file in your photo editor and Save as. Give it the name Copy of
filename 1.jpg
2. Open Copy of filename 1.jpg, Save as and change 1 to 2.
3. Continue doing this until you Save as this file 15 times.
Then you can start opening them and look at them on your screen, when do you
begin to see degradation? Can't see it yet, keep going to 25.
But the real test is not seeing on your screen, you screen magnifies
everything and we don't trust you since you know the number you are looking
at.
Now, print number 1, 3, 9, 15 and 25. Print as large as your printer can
print.
Don't look at the print too closely, just place a little number in pencil on
the back of them. Then, give them to somebody and ask them to place them on
a table in a different order. Can you pick No.1? If you do, try again the
next day. Did you get it again? If you can pick No 1 consistently, then it
does make a difference. If not, no more to argue about.
Then you can ask your tif friends to pick the print they think is the best.
You may be surprised!
Give us the results a few weeks from now.

begin to see degradation? Can't see it yet, keep going to 25.
But the real test is not seeing on your screen, you screen magnifies
everything and we don't trust you since you know the number you are looking
at.
Now, print number 1, 3, 9, 15 and 25. Print as large as your printer can
print.
Don't look at the print too closely, just place a little number in pencil on
the back of them. Then, give them to somebody and ask them to place them on
a table in a different order. Can you pick No.1? If you do, try again the
next day. Did you get it again? If you can pick No 1 consistently, then it
does make a difference. If not, no more to argue about.
Then you can ask your tif friends to pick the print they think is the best.
You may be surprised!
Give us the results a few weeks from now.




"WStoreyII" <papastoreyii@hotmail.com> wrote in message
news:aH%Fb.1376$2o5.1222@newssvr27.news.prodigy.co m...

> Hello,
>
> I have recently learned that jpgs corrupt files. So i opened psp6 and

went

> to convert all the files that i have in to Tiffs however it had an option
> for RGB format or CMYK format. My questions is which one do i use, my
> printer (Epson Stylus Cx5400)uses cmyk color cartridges so i was thinking
> that is what i should use and that i could convert them to rgb if i need

to

> use them for the web or anything.
>
> Please tell me if this is the right assumption and if not what to do.
>
> Thanks & Happy Holidays
>
> WStoreyII
> Emailto: PapastoreyII@hotmail.com
>
>

"Yves Alarie" <rd50@@pitt.edu> writes:

> Everything you are trying to do is incorrect.
>
> 1. Where did you learn that jpg corrupts files? Nonsense.

Not "nonsense". JPEG is lossy compression: you don't get back the same
bits you put into it. Once that happens, of course you can't get back
to the original bits. But that may not be a problem, as JPEG is
designed to throw away information that isn't visible, anyway. Except,
of course, that the degree of compression (and hence the degree of
loss) is adjustable; it's certainly possible to make visible changes
to an image by saving it as JPEG with too much compression.

That said, it seems that every time a JPEG image is loaded, modified,
and saved again can lose more data. Probably not much, but something
to think about if you are processing images through many steps. In
that situation, lossless image storage may be worthwhile.

> 2. Your camera is sRGB, your video display is sRGB.

Well, they are RGB. Quite possibly not sRGB, which is a specific standard.

> All printers are CMYK.

Except those that are CMY, of course .

> There is no sense in saving a picture in CMYK. XP (or any photo software)
> sends your sRGB file to your printer, it is translated automatically to what
> your printer can understand.
>
> If you converted to .tif you will see that these files will be about 10
> times the size of .jpg.

Depending on compression level in the JPEG, of course. And the content
of each image. I just saved an image in TIFF with LZW compression; it
was 518728 bytes. The same image in JPEG (quality 10 from Photoshop 6)
was 232158 bytes. I think you've overstated your case. Almost as badly
as "JPEG corrupts files".

> The only time you want to save in .tif is when you want to edit the file
> many times and "save as" many times.

Exactly.

> We used .tif in the old days because resolution was poor and "save as" jpg
> many times would degrade the image. These days are gone with cameras of 2 MP
> and above.

I'm not sure why I should be glad to lose detail in, say, a 3MP
image. If I pay for a 3MP camera, it would be nice to preserve all
that detail.

> If you want to convert the .tif files back to jpg you can use this free
> batch converter:
> http://www.irfanview.com/
>
> Here is a way to do your own experiment.
>
>
> This used to be correct, in the days of poor resolution digital cameras and
> scanners. Things have changed dramatically and unless you want to print very
> large (by large I mean more than 12 x 18) from a pro shop there is
> absolutely no advantage to save tif files over jpg.

Except you said that editing/saving many times is a situation where
you want lossless compression.

> The first point is, every time you "Save as" a jpg there is a little loss
> and artifacts introduced, so if you edit a picture and you Save as many
> time, there is some degradation with each Save as, but not with Save if you
> use Save to save your changes as you are editing(even if you don't do
> anything to the picture and you Save as just to change the name of the file,
> it is the Save as that is the problem).

Huh? How do you know this?

> So if you plan to edit the file many
> times, keep it in tif until done and then save it as jpg. Since you can
> always saved it back as tif for further editing, no problem.

Exactly.

> The second point is, can you see the difference? Only you can tell, no
> amount of info will convince you. So you do the experiment yourself. It has
> been done many times. Here is how to do it.
> Take one of your jpg file, right click on it and click on Copy. Hold the
> Ctrl key down and press the letter V. This will make a new file in your
> folder "Copy of filename.jpg (note there is no degradation when you do this,
> since you don't open the file and Save as, you only copied it). Now.
> 1. Open this file in your photo editor and Save as. Give it the name Copy of
> filename 1.jpg
> 2. Open Copy of filename 1.jpg, Save as and change 1 to 2.
> 3. Continue doing this until you Save as this file 15 times.

I'm not sure this will show the problem. Certainly closing,
re-opening, and re-saving will.

<snip>

And yes, the experiment sounds like a valid one.

--
-Stephen H. Westin
Any information or opinions in this message are mine: they do not
represent the position of Cornell University or any of its sponsors.

I have seen a lot of debat on this issue today since posting this,

since the general concensus seems to be that since the camera captured the
picture in jpg that it is already damaged (a little) that i can at least
save this on cd in this format and then if i choose to edit save it as a psd
or a tiff.

Thanks for all the Help & Happy Holidays

"Stephen H. Westin" <westin*nospam@graphics.cornell.edu> wrote in message
news:ur7yvqnwp.fsf@graphics.cornell.edu...

> "Yves Alarie" <rd50@@pitt.edu> writes:
>

> > Everything you are trying to do is incorrect.
> >
> > 1. Where did you learn that jpg corrupts files? Nonsense.

>
> Not "nonsense". JPEG is lossy compression: you don't get back the same
> bits you put into it. Once that happens, of course you can't get back
> to the original bits. But that may not be a problem, as JPEG is
> designed to throw away information that isn't visible, anyway. Except,
> of course, that the degree of compression (and hence the degree of
> loss) is adjustable; it's certainly possible to make visible changes
> to an image by saving it as JPEG with too much compression.
>
> That said, it seems that every time a JPEG image is loaded, modified,
> and saved again can lose more data. Probably not much, but something
> to think about if you are processing images through many steps. In
> that situation, lossless image storage may be worthwhile.
>

> > 2. Your camera is sRGB, your video display is sRGB.

>
> Well, they are RGB. Quite possibly not sRGB, which is a specific standard.
>

> > All printers are CMYK.

>
> Except those that are CMY, of course .
>

> > There is no sense in saving a picture in CMYK. XP (or any photo

software)

> > sends your sRGB file to your printer, it is translated automatically to

what

> > your printer can understand.
> >
> > If you converted to .tif you will see that these files will be about 10
> > times the size of .jpg.

>
> Depending on compression level in the JPEG, of course. And the content
> of each image. I just saved an image in TIFF with LZW compression; it
> was 518728 bytes. The same image in JPEG (quality 10 from Photoshop 6)
> was 232158 bytes. I think you've overstated your case. Almost as badly
> as "JPEG corrupts files".
>

> > The only time you want to save in .tif is when you want to edit the file
> > many times and "save as" many times.

>
> Exactly.
>

> > We used .tif in the old days because resolution was poor and "save as"

jpg

> > many times would degrade the image. These days are gone with cameras of

2 MP

> > and above.

>
> I'm not sure why I should be glad to lose detail in, say, a 3MP
> image. If I pay for a 3MP camera, it would be nice to preserve all
> that detail.
>

> > If you want to convert the .tif files back to jpg you can use this free
> > batch converter:
> > http://www.irfanview.com/
> >
> > Here is a way to do your own experiment.
> >
> >
> > This used to be correct, in the days of poor resolution digital cameras

and

> > scanners. Things have changed dramatically and unless you want to print

very

> > large (by large I mean more than 12 x 18) from a pro shop there is
> > absolutely no advantage to save tif files over jpg.

>
> Except you said that editing/saving many times is a situation where
> you want lossless compression.
>

> > The first point is, every time you "Save as" a jpg there is a little

loss

> > and artifacts introduced, so if you edit a picture and you Save as many
> > time, there is some degradation with each Save as, but not with Save if

you

> > use Save to save your changes as you are editing(even if you don't do
> > anything to the picture and you Save as just to change the name of the

file,

> > it is the Save as that is the problem).

>
> Huh? How do you know this?
>

> > So if you plan to edit the file many
> > times, keep it in tif until done and then save it as jpg. Since you can
> > always saved it back as tif for further editing, no problem.

>
> Exactly.
>

> > The second point is, can you see the difference? Only you can tell, no
> > amount of info will convince you. So you do the experiment yourself. It

has

> > been done many times. Here is how to do it.
> > Take one of your jpg file, right click on it and click on Copy. Hold the
> > Ctrl key down and press the letter V. This will make a new file in your
> > folder "Copy of filename.jpg (note there is no degradation when you do

this,

> > since you don't open the file and Save as, you only copied it). Now.
> > 1. Open this file in your photo editor and Save as. Give it the name

Copy of

> > filename 1.jpg
> > 2. Open Copy of filename 1.jpg, Save as and change 1 to 2.
> > 3. Continue doing this until you Save as this file 15 times.

>
> I'm not sure this will show the problem. Certainly closing,
> re-opening, and re-saving will.
>
> <snip>
>
> And yes, the experiment sounds like a valid one.
>
> --
> -Stephen H. Westin
> Any information or opinions in this message are mine: they do not
> represent the position of Cornell University or any of its sponsors.

Just do the experiment yourself.
You have a 3 MP camera. You have the option to save in .jpg or .tif.
Take the same picture, one in jpg and one in tif
Then print. If you think you can tell the difference between one and the
other, then use the one you prefer. No more arguments!
You asked a very good question. The jpg vs tif has been around a long time.
With new camera Christmas gifts, I am sure we will get this question again.
"WStoreyII" <papastoreyii@hotmail.com> wrote in message
news:Wo4Gb.2013$z%6.1660@newssvr29.news.prodigy.co m...

> I have seen a lot of debat on this issue today since posting this,
>
> since the general concensus seems to be that since the camera captured the
> picture in jpg that it is already damaged (a little) that i can at least
> save this on cd in this format and then if i choose to edit save it as a

psd

> or a tiff.
>
> Thanks for all the Help & Happy Holidays
>
> "Stephen H. Westin" <westin*nospam@graphics.cornell.edu> wrote in message
> news:ur7yvqnwp.fsf@graphics.cornell.edu...

> > "Yves Alarie" <rd50@@pitt.edu> writes:
> >

> > > Everything you are trying to do is incorrect.
> > >
> > > 1. Where did you learn that jpg corrupts files? Nonsense.

> >
> > Not "nonsense". JPEG is lossy compression: you don't get back the same
> > bits you put into it. Once that happens, of course you can't get back
> > to the original bits. But that may not be a problem, as JPEG is
> > designed to throw away information that isn't visible, anyway. Except,
> > of course, that the degree of compression (and hence the degree of
> > loss) is adjustable; it's certainly possible to make visible changes
> > to an image by saving it as JPEG with too much compression.
> >
> > That said, it seems that every time a JPEG image is loaded, modified,
> > and saved again can lose more data. Probably not much, but something
> > to think about if you are processing images through many steps. In
> > that situation, lossless image storage may be worthwhile.
> >

> > > 2. Your camera is sRGB, your video display is sRGB.

> >
> > Well, they are RGB. Quite possibly not sRGB, which is a specific

standard.

> >

> > > All printers are CMYK.

> >
> > Except those that are CMY, of course .
> >

> > > There is no sense in saving a picture in CMYK. XP (or any photo

> software)

> > > sends your sRGB file to your printer, it is translated automatically

to

> what

> > > your printer can understand.
> > >
> > > If you converted to .tif you will see that these files will be about

10

> > > times the size of .jpg.

> >
> > Depending on compression level in the JPEG, of course. And the content
> > of each image. I just saved an image in TIFF with LZW compression; it
> > was 518728 bytes. The same image in JPEG (quality 10 from Photoshop 6)
> > was 232158 bytes. I think you've overstated your case. Almost as badly
> > as "JPEG corrupts files".
> >

> > > The only time you want to save in .tif is when you want to edit the

file

> > > many times and "save as" many times.

> >
> > Exactly.
> >

> > > We used .tif in the old days because resolution was poor and "save as"

> jpg

> > > many times would degrade the image. These days are gone with cameras

of

> 2 MP

> > > and above.

> >
> > I'm not sure why I should be glad to lose detail in, say, a 3MP
> > image. If I pay for a 3MP camera, it would be nice to preserve all
> > that detail.
> >

> > > If you want to convert the .tif files back to jpg you can use this

free

> > > batch converter:
> > > http://www.irfanview.com/
> > >
> > > Here is a way to do your own experiment.
> > >
> > >
> > > This used to be correct, in the days of poor resolution digital

cameras

> and

> > > scanners. Things have changed dramatically and unless you want to

print

> very

> > > large (by large I mean more than 12 x 18) from a pro shop there is
> > > absolutely no advantage to save tif files over jpg.

> >
> > Except you said that editing/saving many times is a situation where
> > you want lossless compression.
> >

> > > The first point is, every time you "Save as" a jpg there is a little

> loss

> > > and artifacts introduced, so if you edit a picture and you Save as

many

> > > time, there is some degradation with each Save as, but not with Save

if

> you

> > > use Save to save your changes as you are editing(even if you don't do
> > > anything to the picture and you Save as just to change the name of the

> file,

> > > it is the Save as that is the problem).

> >
> > Huh? How do you know this?
> >

> > > So if you plan to edit the file many
> > > times, keep it in tif until done and then save it as jpg. Since you

can

> > > always saved it back as tif for further editing, no problem.

> >
> > Exactly.
> >

> > > The second point is, can you see the difference? Only you can tell, no
> > > amount of info will convince you. So you do the experiment yourself.

It

> has

> > > been done many times. Here is how to do it.
> > > Take one of your jpg file, right click on it and click on Copy. Hold

the

> > > Ctrl key down and press the letter V. This will make a new file in

your

> > > folder "Copy of filename.jpg (note there is no degradation when you do

> this,

> > > since you don't open the file and Save as, you only copied it). Now.
> > > 1. Open this file in your photo editor and Save as. Give it the name

> Copy of

> > > filename 1.jpg
> > > 2. Open Copy of filename 1.jpg, Save as and change 1 to 2.
> > > 3. Continue doing this until you Save as this file 15 times.

> >
> > I'm not sure this will show the problem. Certainly closing,
> > re-opening, and re-saving will.
> >
> > <snip>
> >
> > And yes, the experiment sounds like a valid one.
> >
> > --
> > -Stephen H. Westin
> > Any information or opinions in this message are mine: they do not
> > represent the position of Cornell University or any of its sponsors.

>
>

Enjoyed your reply and questioning my opinions.
Hope you can join us offering solutions here.

"Stephen H. Westin" <westin*nospam@graphics.cornell.edu> wrote in message
news:ur7yvqnwp.fsf@graphics.cornell.edu...

> "Yves Alarie" <rd50@@pitt.edu> writes:
>

> > Everything you are trying to do is incorrect.
> >
> > 1. Where did you learn that jpg corrupts files? Nonsense.

>
> Not "nonsense". JPEG is lossy compression: you don't get back the same
> bits you put into it. Once that happens, of course you can't get back
> to the original bits. But that may not be a problem, as JPEG is
> designed to throw away information that isn't visible, anyway. Except,
> of course, that the degree of compression (and hence the degree of
> loss) is adjustable; it's certainly possible to make visible changes
> to an image by saving it as JPEG with too much compression.
>
> That said, it seems that every time a JPEG image is loaded, modified,
> and saved again can lose more data. Probably not much, but something
> to think about if you are processing images through many steps. In
> that situation, lossless image storage may be worthwhile.
>

> > 2. Your camera is sRGB, your video display is sRGB.

>
> Well, they are RGB. Quite possibly not sRGB, which is a specific standard.
>

> > All printers are CMYK.

>
> Except those that are CMY, of course .
>

> > There is no sense in saving a picture in CMYK. XP (or any photo

software)

> > sends your sRGB file to your printer, it is translated automatically to

what

> > your printer can understand.
> >
> > If you converted to .tif you will see that these files will be about 10
> > times the size of .jpg.

>
> Depending on compression level in the JPEG, of course. And the content
> of each image. I just saved an image in TIFF with LZW compression; it
> was 518728 bytes. The same image in JPEG (quality 10 from Photoshop 6)
> was 232158 bytes. I think you've overstated your case. Almost as badly
> as "JPEG corrupts files".
>

> > The only time you want to save in .tif is when you want to edit the file
> > many times and "save as" many times.

>
> Exactly.
>

> > We used .tif in the old days because resolution was poor and "save as"

jpg

> > many times would degrade the image. These days are gone with cameras of

2 MP

> > and above.

>
> I'm not sure why I should be glad to lose detail in, say, a 3MP
> image. If I pay for a 3MP camera, it would be nice to preserve all
> that detail.
>

> > If you want to convert the .tif files back to jpg you can use this free
> > batch converter:
> > http://www.irfanview.com/
> >
> > Here is a way to do your own experiment.
> >
> >
> > This used to be correct, in the days of poor resolution digital cameras

and

> > scanners. Things have changed dramatically and unless you want to print

very

> > large (by large I mean more than 12 x 18) from a pro shop there is
> > absolutely no advantage to save tif files over jpg.

>
> Except you said that editing/saving many times is a situation where
> you want lossless compression.
>

> > The first point is, every time you "Save as" a jpg there is a little

loss

> > and artifacts introduced, so if you edit a picture and you Save as many
> > time, there is some degradation with each Save as, but not with Save if

you

> > use Save to save your changes as you are editing(even if you don't do
> > anything to the picture and you Save as just to change the name of the

file,

> > it is the Save as that is the problem).

>
> Huh? How do you know this?
>

> > So if you plan to edit the file many
> > times, keep it in tif until done and then save it as jpg. Since you can
> > always saved it back as tif for further editing, no problem.

>
> Exactly.
>

> > The second point is, can you see the difference? Only you can tell, no
> > amount of info will convince you. So you do the experiment yourself. It

has

> > been done many times. Here is how to do it.
> > Take one of your jpg file, right click on it and click on Copy. Hold the
> > Ctrl key down and press the letter V. This will make a new file in your
> > folder "Copy of filename.jpg (note there is no degradation when you do

this,

> > since you don't open the file and Save as, you only copied it). Now.
> > 1. Open this file in your photo editor and Save as. Give it the name

Copy of

> > filename 1.jpg
> > 2. Open Copy of filename 1.jpg, Save as and change 1 to 2.
> > 3. Continue doing this until you Save as this file 15 times.

>
> I'm not sure this will show the problem. Certainly closing,
> re-opening, and re-saving will.
>
> <snip>
>
> And yes, the experiment sounds like a valid one.
>
> --
> -Stephen H. Westin
> Any information or opinions in this message are mine: they do not
> represent the position of Cornell University or any of its sponsors.

"WStoreyII" <papastoreyii@hotmail.com> wrote in message
news:Wo4Gb.2013$z%6.1660@newssvr29.news.prodigy.co m...

> I have seen a lot of debat on this issue today since posting this,
>
> since the general concensus seems to be that since the camera captured the
> picture in jpg that it is already damaged (a little) that i can at least
> save this on cd in this format and then if i choose to edit save it as a psd
> or a tiff.
>

I have taken this approach. I save the camera's jpg image file to Tiff format. Then I make any
necessary adjustments and resave to the Tiff files. I then archive these Tiff files on CD-R and
convert back to jpg when needed. Continually re-saving jpg's will cause the image to degrade over
time. Experiment for yourself by saving a image file in two formats, one in tiff and the other in
jpg. Then make 4-5 sets of image adjustments, re-saving between each adjustment. You will discover
for yourself which is the better method.

Yves Alarie wrote:

>
> ...there is some degradation with each Save as, but not with Save if you
> use Save to save your changes as you are editing...

Hmm, I did a little test:

Open a drawing, zoom way way way in close and saveas under a different
filename... when it asks for the jpeg compression ratio, slide the bar
way over to 1 or 2 & you can see the effect of the compression as you
slide (PS 5.5). Hold it there for a moment to allow the preview to
calculate. Now, as soon as you click OK to make the save, it returns to
the good quality so what you have in the editor is still tiff quality
(unless you crash). Save or saveas doesn't matter.

I normally save minor crops & adjustments for photo shoots in jpeg
(under a different file name) and I agree it doesn't usually matter much
except very large prints as long as the quality is above 7 or 8. I keep
the original just in case. If it's special I'll save at a quality of 12
which is still smaller than a tiff & it's nice not to have all different
file types (perhaps a trivial point).

Where it does matter though is with a big simple gradually transitioning
sky, especially if you are going to do some increase in contrast with
that. Really detailed fussy pictures will not be affected as much and
won't compress as well in file size either.

Also, photoshop remembers the jpeg quality setting I used last if it was
last saved in photoshop. If direct from the digicam, it doesn't know
what setting to use and takes the last ratio I used before shutting down
photoshop (and rebooting?). But I can close an image that was saved at a
ratio of 2, shut down PS & reopen it, do a blurr & saveas remembers the
2 setting. I'm a little unclear exactly what to expect here but those
are my results.

For important professional products, the hard drive space is cheap though.