PSD: Photoshop’s native file format is great for saving your images with the most flexibility. Because the PSD format supports all of Photoshop’s features, you don’t need to flatten your images — and keeping your layers lets you make changes later. If your file size is very large (4MB or larger), make a TIFF or JPEG copy before printing, flattening all the layers. Don’t send PSD files to the local shop for prints.

TIFF: Although the TIFF file format (as you use it in Photoshop) can save your layers and most other Photoshop features, make sure to choose Layers Flatten Image before sending files out for printing. Layered TIFF files generally are compatible only with programs in the Creative Suite. If you don’t flatten the image prior to saving as TIFF or if you elect to include layers when saving as TIFF, Photoshop presents you with a gentle reminder.

JPG: JPEG, as it’s called, is actually a file-compression scheme rather than a file format, but that’s not important. What is important is that JPEG throws away some of your image data when it saves the file. Save important images in PSD or TIFF and use JPEG only for copies. When should you use JPEG? When sending images to a photo lab that doesn’t accept TIFF files and when sending images (perhaps by e-mail or on CD) to people who don’t have Photoshop. Unlike PSD and TIFF, you can open JPEG images in a Web browser and print from there — and so can Granny, and Cousin Jim, and that overseas soldier you adopted. When saving JPEGs, the lower the Quality setting you choose in the JPEG Options dialog box, the smaller the file but also the more damage to the image. I discuss saving as JPEG in more detail in the sidebar, “Resaving images in the JPEG format.”

PDF: It’s easy to overlook Adobe’s PDF format when talking about photos, but you should consider using this format. Although the local photo lab probably won’t accept it, it’s a great format for sharing your pictures with folks who don’t have Photoshop. Unlike JPEG, your images won’t be degraded when saving as PDF; and like JPEG, just about anyone with a computer can view the files. (Adobe Reader, which you can use with PDFs,
is found on just about every computer now, just like Web browsers for JPEG.) Keep in mind, however, that PDF files are larger than JPEGs.

Large Document Format (PSB): Really, really, really big pictures over 30,000 pixels wide or long or both need to be saved in the PSB file format. Will you ever need this format? Consider that 30,000 pixels at a
photo-quality resolution of 300 ppi is 100 inches long. At a resolution of 85 ppi, more appropriate for a long banner to hang in a hallway, you’re talking about artwork that stretches almost 30 feet! Can your printer do that? If not, you probably don’t need the PSB file format. You could theoretically use a number of other available formats, such as DCS, PNG, and Photoshop Raw, but there’s no real need with the more common and more versatile formats about which you just read.

If you’re working with photos from your digital camera and you want to save them as JPEG but that format isn’t available in the Save As dialog box, convert the image to 8-bit color with Image > Mode > 8-Bits/Channel. If you shot the image in Raw (or TIFF) and need to save as JPEG, you’ll have to convert to 8-bit color because JPEG doesn’t support 16-bit color.