OK to change photo file formats?

[Bill Murmann]

I use digital photos in publications I produce for three of my customers.

In the past, I've sent photos by e-mail to my commercial print shop after importing them as JPEGs and converting them to TIF images for editing and enhancement.

The printer and I are limited to using dial-up modems, and the TIF images take a long time to transmit.

I've been wondering if I can change the procedure and speed things up by converting my photos from TIFs back to JPEGs before e-mailing them to the print shop.

Will this work without degrading the quality of the photos?

I'm concered about possibly losing image quality if I import a JPEG, convert it to a TIF, edit the TIF, and then convert it back to a JPEG before e-mailing it to the print shop.

I don't have a lot of experience at this sort of thing, so I'd appreciate any suggestions and comments. Thanks.

--Bill

[terrie]

>>bill murmann: I'm concered about possibly losing image quality if I import a JPEG, convert it to a TIF, edit the TIF, and then convert it back to a JPEG before e-mailing it to the print shop.

You should be fine...the problem arises when you do multiple saves of jpg's...

Saving a jpg to tif and then back to jpg will get around that problem.

One thing you need to consider when going from tif to jpg is chosing the compression number for the jpg. Basically, the lower the number, the greater the "loss" of data so keep that in mind...

Terrie

[Bill Murmann]

Thanks, Terrie. I'm afraid I'm not clear about what a compression number is. When I convert the file formats, I get a dialog box to set the dpi. Is that the compression number?

I usually save both TIF and JPEG files at 350 dpi.

--Bill

[Stephen Owades]

>>bill murmann: I'm concered about possibly losing image quality if I import a JPEG, convert it to a TIF, edit the TIF, and then convert it back to a JPEG before e-mailing it to the print shop.

You should be fine...the problem arises when you do multiple saves of jpg's...

Saving a jpg to tif and then back to jpg will get around that problem.

One thing you need to consider when going from tif to jpg is chosing the compression number for the jpg. Basically, the lower the number, the greater the "loss" of data so keep that in mind...

Terrie
What distinction are you making between what Bill wants to do and "multiple saves of jpg's"? He's planning on going through a second generation of jpeg compression, which will cost something in quality, and I don't see how he'll "get around that problem" as you said. Obviously he wants to do some sort of editing of the image, which means the new jpeg will be different from the original. How much degradation is involved will be affected by the quality setting (compression number?) and file size he chooses when making the new jpeg.

[Robin Springall]

Be careful, Bill: sometimes a jpeg will print badly or even not print at all - it depends on how it goes through your printer's rip. At our studio we produce Press PDFs and send 'em to the printer by email or FTP (we even did it with dial-up). Before that, we used to mail them a CDR and a colour printout, so image size wasn't a problem, then the printer would post us a matchprint.

[Bill Murmann]

Thanks for your help, Robin. Perhaps it would be a good idea to send some test photos to my print shop.

I would start with a JPEG, convert it to a TIF, edit the TIF image, and then convert the edited TIF image back to a JPEG for e-mailing to the print shop. The printer would then import the JPEG into his system.

I hope something like this will work without a loss of image quality. (??) It sounds complicated, though--and "complicated" often means trouble. <s>

--Bill

[ktinkel]

It sounds complicated, though--and "complicated" often means trouble. <s>True enough. But sometimes insisting on “simple” also means trouble.

Although, like you, I try to avoid complexity, sometimes it works. It’s all about this computer stuff! <g>

[Bill Murmann]

<<...sometimes insisting on "simple" also means trouble...>>

I know what you mean. <s>

Do you think my file-conversion idea might work, Kathleen? Taking an original JPEG image, converting it to a TIF format at 350 dpi, editing the TIF image, and then saving it as a JPEG at 350 dpi to e-mail it to the print shop for production?

If this will work without degrading the quality of the image, it will save lots of time on the dial-up modem.

BTW, my printer is not a happy camper. So far, the phone company doesn't offer high-speed Internet service in his part of the city. He *has* to use a dial-up modem.

I can live with dial-up because I don't do that many photos. The printer, however, has lots of other customers besides me. Must be frustrating.

--Bill

[Steve Rindsberg]

Bill,

Does your software allow you to set the "lossiness" of the compression level on your JPGs? The more compression, the smaller the JPG, of course. And the worse the quality of the image. In theory you should be able to set the compression to lossless and get the same image as was in your TIF; no degradation. But this may not produce all that much smaller an image.

I'd test.

[Bill Murmann]

I'm not sure, Steve. I'm afraid I'm getting in over my head. I don't understand "lossiness" and don't know much about digital photo formats in general. My Paint Shop Pro software will convert from and to a long list of formats, but unfortunately I don't know anything about them. I think I heard here in the DTP forum years ago that TIFs are good things, so I use that format for photos and clipart.

My commercial printer likes TIFs, but I'm in the dark about the technical side of all this.

I agree with your suggestion. Testing would be a good idea.

--Bill

[Steve Rindsberg]

I'm not sure, Steve. I'm afraid I'm getting in over my head. I don't understand "lossiness" and don't know much about digital photo formats in general. My Paint Shop Pro software will convert from and to a long list of formats, but unfortunately I don't know anything about them. I think I heard here in the DTP forum years ago that TIFs are good things, so I use that format for photos and clipart.

My commercial printer likes TIFs, but I'm in the dark about the technical side of all this.

I agree with your suggestion. Testing would be a good idea.

--Bill
Lossiness in a nutshell: by throwing away certain image data, you can make the image more compressible. Simple example, consider image data that looks like:

1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 1

Converting the anomalous "2" to "1" might make it possible to represent the data as

1 16
(1 16 times) instead of
1 8 2 1 1 7
(1 8 times, 2 one time, 1 7 times)

Two bytes instead of 6. Not bad. Even if it does damage your image a wee little bit. ,-) That's the "lossy" part.

If your app lets you set the "Quality" level for JPGs, it's letting you adjust how aggressively it does this sort of thing.

In my ancient copy of PaintShop Pro, this is called Compression Level and you set it by clicking Options after choosing JPG as the file type in the Save As dialog box.

I'd be inclined to stick with TIFs if that's what makes you and your printer happy (and the telecomms end of things don't get out of hand)

[Cristen Gillespie]

Thanks for your help, Robin. Perhaps it would be a good idea to send some test photos to my print shop.

I would start with a JPEG, convert it to a TIF, edit the TIF image, and then convert the edited TIF image back to a JPEG for e-mailing to the print shop. The printer would then import the JPEG into his system.

I hope something like this will work without a loss of image quality. (??) It sounds complicated, though--and "complicated" often means trouble. <s>

--Bill

The loss of data with a JPG basically comes from the first "save" and then each save on top of that creates an incremental loss. If you're starting with JPG, you can do your edits in JPG so long as you only make the save once. I myself, anyway, can't see the advantage to converting to TIF used as you have described. You've lost some data once (presumably when you used your camera to compress the JPG, and you'll lose some again when you save as a JPG again. The TIF is a red herring, I think. It's not going to help you, unless you save intermittently between the open, edits and save of the final JPG.

I'm with Steve on sticking with TIF. I get 10Mb per hour on dialup, and I can manage most single-layer images. I'd convert to TIF and then use a good zip or sit program to "package" the file. There's less chance of corruption, and zip or sit often can compress losslessly to help with file size. (I use Stuffit, and it usually does compress the file size.)

[Bill Murmann]

<<...I'd be inclined to stick with TIFs...>>

Thanks for explaining lossiness, Steve. TIFs are looking better and better. I'll share all this with my printer. Hopefully, between the two of us we can work out an efficient way of dealing with photos that will preserve quality.

I'll also check my Paint Shop Pro software. I have an old version that I've been using simply because I'm familiar with it--or at least with *some* of it. <s>

I also have the very latest version of PSP that has all the newest bells and whistles. I have to learn how to use it, however. I often wonder why "new and improved" usually means "complicated" and "hard to learn"? <s>

--Bill

[Bill Murmann]

<<...I'm with Steve on sticking with TIF...(etc.)...>>

Hi Cristen,

Your suggestion to ZIP my TIF images sounds like the best bet.

My printer once suggested sending him the original JPEG images. However, the photos I use have to be converted to greyscale, and generally have to be cropped, sized, and corrected for brightness and contrast, etc. My printer is really good and I've worked with him for over 15 years, but I had some bad experiences in the past when I've trusted other printers (and typesetters) to make "editorial" decisions. I prefer to do the work myself, whenever possible.

And, actually, I think my printer like this arrangement, too. Might involve less work...<s>

--Bill

[Steve Rindsberg]

<<...I'd be inclined to stick with TIFs...>>

Thanks for explaining lossiness, Steve. TIFs are looking better and better. I'll share all this with my printer. Hopefully, between the two of us we can work out an efficient way of dealing with photos that will preserve quality.

I'll also check my Paint Shop Pro software. I have an old version that I've been using simply because I'm familiar with it--or at least with *some* of it. <s>

I also have the very latest version of PSP that has all the newest bells and whistles. I have to learn how to use it, however. I often wonder why "new and improved" usually means "complicated" and "hard to learn"? <s>

--Bill
I'm with you on that. Maybe I haven't upgraded my perceived needs as fast as I might, but PSP 4 seems to most everything I routinely need to do with images. (To be fair, that's not a lot, and very little of it's in the image editing department).

Hey, I got the email about upgrading to Eudora 4 from 3 - seems 4 could [much snippage of breathless marketing prose] do HTML email. That seemed like reason enough not to update. And 3 still works nicely for the most part.

[Robin Springall]

Steve's right, of course, about how the quality of jpegs deteriorate with consecutive saves. I sympathize with your dial-up plight, but I've found that WinZipping a graphic file won't reduce its size more than around 5%. If you really have to use jpegs to reduce transmission time, it's imperative to get some kind of proof from the printer: either on paper, posted to you for approval, or a PDF sent by email. Many RIPS and CTP systems can't handle jpegs reliably and consistently, and CMYK jpegs in particular!

[Bill Murmann]

Thanks, Robin. As you suggest, I can see that working with digital photos requires a lot of care.

I think that computer technology has introduced a whole new set of complexities into publishing. Back in the "old days" handling photos seemed a lot more straightforward. I would give Tri-X black & white prints to the printer who would shoot them with that huge camera they had in the back shop and that would be it. No JPEGs, no TIFS, no image editing, etc. Life was a lot simpler. <s>

--Bill

[Bill Murmann]

<<...but PSP 4 seems to do most everything I need...(etc.)...>>

I recently purchased PSP 9. Before I could even use it, I had to install more RAM in my four-year-old Pentium III.

I'm just starting to experiment with PSP 9. It has a lot of image-editing tools and features like a 1-click photo fix, and the ability to add fill-flash to a photo, etc. I'll concentrate on learning the parts that deal with digital photos.

Frankly, the other features of the software are more suited to graphic artists. It would be nice to know how to do these things, but I think I'll be better off leaving the graphic-artist stuff to the pros.

--Bill

[Cristen Gillespie]

I agree with you taking care of it. I don't think you should hand off editorial decisions to anyone else. You know the size, greyscale is smaller than RGB, and if your printer has given you the max resolution you need, you can make sure you're not sending any extra data. On dialup, that really hurts<G>

If you have to send a lot of pictures, you're going to suffer. I make sure I have something else to do just to be able to stand the upload times. Not fun for those of us still stuck out in the boonies.

I entirely sympathize with you on learning new software. New and improved occasionally means faster and easier, but just as often (more often?) means complicated and difficult to work into your workflow efficiently<G>

[Bill Murmann]

<<...I make sure I have something else to do just to be able to stand the upload times...(etc.)...>>

Yes, me too. Although I've found that I have to keep an eye on the progress of the upload. Sometimes, the online link will disconnect in the middle of a file transfer. When this happens, there is often a cryptic message about "Protocol timed out...disconnecting..." I have never understood exactly what was going on--except for being disconnected, of course. That part is always clear. <s>

To sort of get around this problem, I attach photos to separate messages--one or two per e-mail. This seems to work better than trying to send three or four photos as attachments to a single e-mail. Something almost always goes wrong when I try to do that.

Clipart, however, seems to be easier to send as e-mail attachments. And text files work really well.

--Bill

[PeterArnel]

Bill I have only just logged on to this but doesnt your printers have FTP sites. Its by far the quickest way to send files.
Peter
As far as how you do it - there is only one way and that is to talk to your printer, send test files exactly as agreed - get hard copy proofs back ( scatter images on a printed sheet would be best) and then follow the procedure for the real job. This is the only way to tackle technology changes these days

[Bill Murmann]

<<...This is the only way to tackle technology changes these days...>>

Thanks very much, Peter. I will definitely be talking with my printers. I currently work with three shops, so it will be interesting to see if we develop three different procedures. <s>

--Bill

[PeterArnel]

Good - I am sure they wont "BS" you ( as if we printers would do the :-) ). regardless of what the proofs are like - look at the final printed product ( which I am sure u will do) . In fact the only true test of quality is for u to be a sleeper on a mailing list

Peter
I know of a printer that has one press just printing file copies ( not me I might add)

[Bill Murmann]

Thanks, Peter. As always, I appreciate your suggestions. --Bill

[JVegVT]

>> If you're starting with JPG, you can do your edits in JPG so long as you only make the save once. >>

According to "JPEG Myths and Facts" by Sue Chastain (http://graphicssoft.about.com/od/formatsjpeg/a/jpegmythsfacts.htm), you don't lose quality from repeated saves *within the same editing session*. It's saving, closing your editing applications, reopening, and saving again that degrades the image each time. But you don't degrade the image each time you save unless you also close, which results in a recompression. Here is what the article says:

"JPEGs lose quality every time they are opened, edited and saved.

"True. If a JPEG image is opened, edited, and saved again it results in additional image degradation. It is very important to minimize the number of editing sessions between the initial and final version of a JPEG image. If you must perform editing functions in several sessions or in several different programs, you should use a image format that is not lossy (TIFF, BMP, PNG) for the intermediate editing sessions before saving the final version. Repeated saving within the same editing session won't introduce additional damage. It is only when the image is closed, re-opened, edited and saved again."

That is quite a bit less scary than losing quality with every save *while you are in one editing session*.

And by the way, zipping a file is lossless unless something goes wrong. You shouldn't lose anything when you zip a TIF.
--Judy M.

[JVegVT]

>> New and improved occasionally means faster and easier, but just as often (more often?) means complicated and difficult to work into your workflow efficiently<G> >>

Well, most likely the reason they put out a new version is that it does more than the old version. So of course, we have to learn how to use the new features. If they're nothing we care about, the solution is simple: keep on using the old version.
--Judy M.

[JVegVT]

>> ? Taking an original JPEG image, converting it to a TIF format at 350 dpi, editing the TIF image, and then saving it as a JPEG at 350 dpi to e-mail it to the print shop for production? >>

The dpi you save it at is completely irrelevant. Your JPEG image has a certain number of pixels. If you convert it to TIFF, it still has the same number of pixels. If you save it again as JPEG, it has the same number of pixels.

To change the number of pixels you have to resample the image, either reducing the number of pixels or increasing the number. These are not good things to do on pictures that are going to be printed. If you increase the number of pixels, your software has to guess what shade the added pixels should be. Reducing the number (downsampling) has a better chance of being successful, within limits. Your software has to decide what pixels to discard.
--Judy M.

[Stephen Owades]

>> If you're starting with JPG, you can do your edits in JPG so long as you only make the save once. >>

According to "JPEG Myths and Facts" by Sue Chastain (http://graphicssoft.about.com/od/formatsjpeg/a/jpegmythsfacts.htm), you don't lose quality from repeated saves *within the same editing session*. It's saving, closing your editing applications, reopening, and saving again that degrades the image each time. But you don't degrade the image each time you save unless you also close, which results in a recompression. Here is what the article says:

"JPEGs lose quality every time they are opened, edited and saved.

"True. If a JPEG image is opened, edited, and saved again it results in additional image degradation. It is very important to minimize the number of editing sessions between the initial and final version of a JPEG image. If you must perform editing functions in several sessions or in several different programs, you should use a image format that is not lossy (TIFF, BMP, PNG) for the intermediate editing sessions before saving the final version. Repeated saving within the same editing session won't introduce additional damage. It is only when the image is closed, re-opened, edited and saved again."

That is quite a bit less scary than losing quality with every save *while you are in one editing session*.

And by the way, zipping a file is lossless unless something goes wrong. You shouldn't lose anything when you zip a TIF.
--Judy M.
When you are working with an image in Photoshop, saving as JPEG applies JPEG compresion to the file written to disk, but the "working copy" within Photoshop hasn't been compressed. Each save generates a new JPEG, but the starting point is the current (non-compressed) working copy, not the previously-saved JPEG file. It is for this reason that you can save repeatedly from within Photoshop without causing further degradation.

But if you start by opening a JPEG file, perform edits, and then save, you have added a second stage of lossy JPEG compression to your original. That degradation happens regardless of how many intermediate saves you do from your working copy.

[JVegVT]

>> if you start by opening a JPEG file, perform edits, and then save, you have added a second stage of lossy JPEG compression to your original. >>

Because you're opening a file already saved (by something as JPEG), editing, and saving, so the file will have additional losses due to compression, right? But saves within that editing session won't further degrade the file, just the final save before you close. When you reopen, the whole process starts again, resulting in more degradation.
--Judy M.

[Stephen Owades]

>> if you start by opening a JPEG file, perform edits, and then save, you have added a second stage of lossy JPEG compression to your original. >>

Because you're opening a file already saved (by something as JPEG), editing, and saving, so the file will have additional losses due to compression, right? But saves within that editing session won't further degrade the file, just the final save before you close. When you reopen, the whole process starts again, resulting in more degradation.
--Judy M.
Exactly right.

[Bill Murmann]

<<...The dpi you save at is completely irrelevant...(etc.)...>>

Thanks, Judy. I thought it would be a good idea (?) to convert the .jpeg image to a .tif for editing purposes. For example, to convert the image to greyscale, to change the brightness or contrast, etc. in a .tif format and then to convert the edited image back to .jpeg format for e-mailing with a dial-up modem.

I'm working with the assumption that making changes in a .jpeg would result in damaging the image. (??)

--Bill

[JVegVT]

Sorry to be so late in replying. I did some major hard drive changes in two computers and didn't have time for my online forums.

>> I thought it would be a good idea (?) to convert the .jpeg image to a .tif for editing purposes. >>

I agree that it makes sense to convert a JPEG to a TIF before you do any editing. That way you have a copy that won't degrade as you save, close, and reopen. When you finally do convert it to JPEG, you'll degrade it again, depending on how much compression you apply.

As you have probably gathered from this thread, converting your JPEG to TIF and completing your edits in one session and then saving as JPEG will not degrade the picture any more than just opening the JPEG, doing all your edits in one session, and saving it again as JPEG. Several saves within one editing session do not degrade the JPEG with every save. It's the final save that applies additional compression, and if you open the file again for further editing, you will be dealing with a photo that is degraded more than the JPEG that you started with.

I feel it's important to have an uncompressed copy of a file you are going to edit and then work on a copy of it. That way, if you mess up, you have an "original" you can go back to. If I were in your circumstances, I wouldn't want to convert the final copy to JPEG after editing. If you apply enough compression to reduce the file size appreciably, you'll be degrading the image and risk having artifacts and unwanted noise in it. If you don't compress much, you won't get the small size you want. I think I'd Zip the TIF file instead of saving it as JPEG. Zipping is lossless. Or save as a compressed TIF if the software you're printing it from can deal with a compressed TIF.

You can't get broadband where you are? That's my worst nightmare!<g> Really, once you have it, you can never go back to dialup. But if it's not available, it's not available. Such is life.
--Judy M.

[Bill Murmann]

<<...I agree that it makes sense to convert a JPEG to a TIF...(etc.)...>>

Thanks, Judy. You've put everything in a nutshell, which makes for good reference material. There is a lot of good advice in this thread.

Sometimes I wonder if printing had this many complications and issues back in the Dark Ages before computers and all of this digital stuff? <s>

Having said this, however, I will admit that because of computers and digital stuff I can personally do things with publications that would have been impossible 20 years ago.

--Bill

[Molly/CA]

Bill, I had a long message about compressing and somehow got VB to eat it. Present issues first:

Much depends on the size the picture will be when printed, and the quality of the printing. There's little point sending a huge and high-res image if it's going to be printed the size of a postage stamp and with big fat dots (I'm so dumb I don't know the terms --coarse screen?). If you're going for a half-page in a big glossy photo-focused publication, the best is barely good enough.

Daryl, of CS's Garden forum, publishes in gardening and landscaping magazines (see def above) and says that many now accept JPEGS and have utilities for fixing them so they print right.

You can probably most quickly arrive at an understanding of how compression and resizing and import/export ("save as") of pictures works by spending a session playing. BTW I find TIFs a pain to work with so immediately save any JPG I plan to edit as a PSD. The file size will be about the same, you'll have all the layering etc. options available (forever), and PS won't gripe at you when you go to save a file you've added text to or adjusted with layers.

About compression. Think of old novels in which people communicate by telegram. They drop out bits -- "The file size will be about the same" becomes "File size about same." You can think about JPG compression the same way. And every time you save a JPG to a JPG it applies the compression technique again --even if you have an "original quality" save in your program. You can get away with it once, to crop a snapshot to e-mail to a friend, for instance, but for serious work you want to save all the pixels in the picture just as they are --insofar as possible.

You can test the effects for yourself quite easily. Open a nice big picture whose "original" format is JPG --from your camera at its best quality or wherever. (If you have a camera that will save to a RAW file, you could take a couple pictures for the purpose and click the shutter twice --save to best JPG once, to RAW for the duplicate. Comparing the end results below should _really_ straighten you out.)

Immediately save to a non-compressing format --PSD, BMP, TIF, whatever you're comfortable with. (I'm a klutz so I keep original JPGs in their own folder so I can't accidentally overwrite to the same filename --"save as" to a different folder.) Now start saving to JPG. When you do this your program should have a slider with the compression options, usually numbered, or something that gives you numbered choices for the save. (If your choices are only "medium" "best" etc I'd look for another program.) A lot of programs now compute the approximate file size for each level as you go, and most have a "preview" utility. Thumbs Plus has an especially nice one, that shows a zoomed (you can change it) bit of the picture and lets you shuttle between the original and the projected JPG.

Note that as you play with the slider, the file size reaches a minimum and then, as you go down the scale towards "rotten," increases. The same thing happens in the other direction. A JPG can "compress" to a larger size than the original if you get overenthusiastic! The optimum in PS is usually around 7 --don't ask me why.

Another thing the ultimate file size depends on is the nature of the picture. I take a lot of "landscape" pictures --shrubs and things-- and they are very "busy" with almost every pixel different. At the extreme, the smallest JPG is hardly smaller than the original and the only way to get something to e-mail or post at a reasonable loading size is to resize the picture. At the other end, a picture of a sailboat on a large lake with a large clear sky might compress to practically nothing --lots of duplicate pixels, or pixels that the compressing machine considers alike anyway.

Now you've played with the scale, make some reference pictures. Do a bunch of "save as's" to JPG at different compression levels. Rename each time, of course --TestPic00, 01, and so on. Then take one of the good ones --one saved to the "optimum" size or a bit above --and save it onto itself several times. Then get the last one and the original onto the screen side by side.

OK, end of first lesson. Now. Your program should have a "resize" utility, and its dialogue box should show the resolution, something that will give you a clue to the file size after resizing, and the picture size. Photoshop's resize dialogue is especially easy to use as you can change the units to whatever you think in --inches, pixels etc. , and it tells you the file size as you fiddle with the new size.

Here is something the "PhotoshopCS Bible" spelled out for me --reducing the size is the same as reducing the resolution, when you think in terms of displaying the picture at the same size as before. Suppose you had 10,00 pixels or dots making up the picture (in reality more like a million or six) --100 across and 100 down. If the original picture was 5x5 inches on your screen and you resize it to half, then display it at 5x5 again, you'll be putting the picture together with a lot less dots (not mathematically exactly proportional to the size, because the program uses a system rather comparable to compression for deciding how to deal with the pixels).

Sometimes you can reduce file size by resizing --again, depending on the eventual output. If you've been sent a picture whose "size" is 17" across and it will be printed 3" across (some columns, with the picture margin), you might do just as well with a picture reduced somewhat. (Quality of reproduction is also a factor here.) Someone here should know the ratios that work best. I think you wouldn't make the picture the ultimate size of 3" but give it a bit of Tennessee windage. For some reason I have better luck resizing than reducing resolution outright. Again, someone here will explain this, I hope.

So if you want to explore further, do another batch of saves and resize, saving to the same format (PSD/TIF) with new names, and then play with displaying (or even printing if you want to waste the ink) the pictures side by side at the same size. (It wouldn't hurt to copy the first PSD to the same directory as the original JPG, so if you screw up and save the 3" file on top the 17" one you have a backup.)

As you'll have seen from messages here, some operations change the quality of the picture even though it's in TIF/PSD or whatever. Rotating and straightening are among them, and I think resizing. PhotoshopCS's help manual is (for a change) actually helpful about mentioning this on a case by case basis. I'm sure there's an optimum order for doing things so that the original pixels remain as intact as possible until you're ready to change them --I crop first, then rotate if necessary, then adjust (levels, color, contrast, etc.), then add text. At this point, or sometimes before I do the text if it's simple, I save the file. THEN I resize, if necessary, and save to a JPG if for posting on a forum or sending in an e-mail. This preserves all the hard work and prevents flattening the layers (for a JPG) and inadvertently welding them inextricably to the picture. CS just saves a layered picture as a copy automatically --heaven! (Until you do a lot of work on a non-layered PSD, forgetting to save, and "save as" a JPG, whereupon you have the original without all the hard work you did on it and a JPG with all the corrections and additions.

I hope this helps, and I expect this discussion to continue with all kinds of corrections and tips that will help me, too! It's been really useful, where not totally over my head ;)