Oops-forgot PDFs!
PDFs are mighty versatile, you can use them for:
1) Sending images to someone else to view (perhaps comps to a client). They're especially nice because pretty much anyone can read them these days, while they might not be able to read your native application files (InDesign, PSD, etc.), or even a TIFF file (I'm thinking here of non-designer folks). Plus they're usually a lot smaller than a corresponding TIFF or native application file.
2) Sending images to print. PDFs are quickly becoming the standard file format to send to printers. Usually you will create your PDF from Indesign or the like (since that's where you did you're final assembly, including importation of your image files which can still be in PSD, TIFF or whatever you prefer), but you can also create a PDF from Photoshop.
3) Creating documents for the web. This is usually something you would do from your page layout program (e.g., creating a PDF manual for distribution on your web site). If you're creating images for use from Photoshop you'll want to go the JPEG or GIF route. One point of distinction: PDFs created from InDesign (we'll stick with Adobe for this discussion!) retain true text, meaning viewers can copy and paste it if they need to. However, if you create a PDF from Photoshop, any text will be rasterized (i.e., will become part of the image-a 'picture of the text' in other words), so viewers will not be able to cut and paste it. Not to mention it will render at the resolution of the file (72 dpi, 100 dpi, whatever), and so will likely be blurry (and unreadable at smaller text sizes). Page layout PDFs still display text as text so readability isn't compromised.
I'm glossing over many subtleties but that should be enough for a general overview....
Tim
