After you have the concept of resampling under your belt, how do you know what size you should be resampling to? How many pixels do you need? Here are your general guidelines:
Photos for your inkjet printer:
Inkjet printers are stochastic printing devices: That is, they use a series of droplets to replicate each pixel in your image, as shown in Figure 2-12. In theory, the optimal image resolution is ƒ1?3 of the printer’s rated resolution.
For example, a printer rated at 720 ppi works best with images at 240 ppi.
1,440 ppi printer, the formula calls for an image resolution of 480 ppi (and that goes for the 2,880 x 1,440 printers, too). However, most folks find that regardless of the printer’s rating, they never need an image resolution higher than 300 ppi.
Web images: Ignore resolution. Ignore the entire Document Size area of the Image Size dialog box. Consider only the image’s pixel dimensions. Determine what area of the Web page the image will occupy and then resize to exactly those pixel dimensions.
Page layout programs and commercial printing: If your image is to be placed into a page layout program’s document and sent to a commercial printing facility, you need to know the line screen frequency (the resolution, so to speak) of the printing press on which the job will be run. Ask the print shop or the person handling the page layout. Your image resolution should be either exactly 1.5 times or exactly twice the line screen frequency. (You shouldn’t notice any difference in the final printed product with either resolution.)
PowerPoint presentations and word processing documents: Generally speaking, 72 ppi is appropriate for images that you place into a presentation or Word document. You should resize to the exact dimensions of the area on the page or slide that the image fills.

In this wonderful world of digital imaging, you see resolution used in four basic ways:
Image resolution: Image resolution is the size of your image’s individual pixels when you print. I go into greater detail about this concept in the upcoming section, “Picking an image resolution.”
Camera resolution: Digital cameras capture each image in a specific number of pixels. Check your camera’s user guide or open one of the images in Photoshop and choose Image? Image Size. Take a look at the number of pixels that your camera records for the width and for the height. Multiply the numbers together, divide by one million, and round off the result. (If you’re in the camera maker’s marketing department, make sure that you round up.) That’s the megapixel (MP) rating for the camera. Use it as a general guideline when shopping. If you create Web graphics or snapshot-size prints, 3 or 4 MP is fine. For large prints, you need at least 6 MP.
Monitor resolution: Monitor resolution determines how many pixels are visible on-screen. Whether you use a Mac or a PC, you set the monitor resolution at the system level (as shown in Figure 2-4). When you use a higher monitor resolution, you get a larger workspace, but each pixel is smaller, which might make some jobs tougher. Experiment to find a monitor resolution that works just right for you.
Mac: Click the blue Apple menu in the upper-left corner of the screen and choose System Preferences. Then click Displays. (Some Apple monitors have a button on the bezel that automatically opens the window for you.)
Windows: Choose Start?Control Panel and then double-click Display. Click the Settings tab to see what monitor resolutions are available.
Printer resolution: Unlike the three preceding terms, printer resolution doesn’t involve pixels. Rather, a printer resolution tells you how many tiny droplets of ink are sprayed on the paper. Remember that it takes several droplets to reproduce a single image pixel — you certainly don’t need an image resolution anywhere close to the printer’s resolution!
(See the following section for more on this.)

Don’t spend money for a terrible passport picture that you’ll be embarrassed to show to strangers all over the world. You can take your own shot, and make great first impressions instead.

Why is it that whenever you have an official photograph taken, you’re made to look like a criminal or terrorist? Sometimes, you don’t have a choice in the matter, such as for your driver’s license (or booking at the county jail). But when it comes to passport photos, you can submit your own picture, and I recommend you do.

There are general requirements for an acceptable photo:

• Photographs must be identical and recent (within six months), with a clear full-face and front-view image. They may be in color or black and white.

• The photographs must be at least 2″ 2″ (5cm 5cm), exclusive of any white borders. The image size, from the bottom of the chin to the top of the head (including hair), should measure between one inch and one and three-eighth’s inches. There should be at least one half inch between the top of the head and the photograph’s border.

• There must be a clear contrast between the background and the image of the subject. The background of the photographs must be white. Grainy photographs cannot be accepted.

Easy enough, right? Now let’s talk about actually taking the picture, because that’s the important part. Here is the equipment you’ll need:

• Digital camera with a self-timer or remote release

• Tripod or alternative way to position the camera

• Two pieces of white foamcore, cardboard, or some other sturdy, reflective surface

• A stool or something else to sit on

• Inkjet printer with photo paper, preferably with matte surface

You want to avoid that stark, deer-in-the-headlights appearance that’s usually caused by using a single flash in a darkened room. You might still use a flash for your shot, but if so, it should be a fill flash and not the sole source of illumination.

Look for a well-lit area that has a white or light background. You might use a brightly lit room in the house (with lots of light coming through one or more windows) or an outdoor setting, where you can use the side of the house for the background. But you don’t want the sun shining right in your eyes. Diffused light is better.

Position your sitting stool at least five feet away from the background. You don’t want to record much background detail. Instead, you want the background a little out of focus, and distance is the best way to create that effect.

Put the camera on the tripod and point it at the sitting stool. A trick I like to do is to put a lamp on the stool to act as my model while I’m aligning the camera. If you have a helper for this project, that person can serve as your stand-in. Position the camera slightly above eye level of the subject. By doing so, the picture will be more flattering and, if you do use a fill light, the shadows will be cast downward and out of the picture.

For your first test shot, turn off the flash. Let’s see how it looks with natural light only. Turn on the self-timer, have a seat, smile slightly, and hold still until the camera has recorded the image.

How does it look? If one side of your face is too shadowy, then position one of the pieces of white foamcore so it reflects light onto the dark side of your face. Try another exposure and make more adjustments to the reflectors until you get something you like.

Sometimes, you just can’t get enough pop in the image if the room lighting is too flat. In this situation, turn on the fill flash function. If you camera has a control for flash exposure compensation, set it to -1. The goal here is not to have the flash serve as the main light source. Instead, you just want a little additional pop to augment the ambient lighting.

If you print your images yourself at home or the office, you can stick with the original format or use the PSD Photoshop format. If you send the photos to the local camera shop (or discount store) for printing, stick with JPEG — or, if they accept it, TIFF. Here are the pros and cons of the major formats that you should consider for photos:

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.