Resolution revelations

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. But remember that a camera with lower resolution using an excellent lens generally produces a better print than a camera with more megapixels using a less expensive lens.
• 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.
• 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.)

Resolving image resolution

Image resolution is nothing more than an instruction to a printing device about how large to reproduce each pixel. On-screen, when working in Photoshop, your image has no resolution at all. An image that’s 3,000 pixels wide and 2,400 pixels tall looks and acts exactly the same in Photoshop whether you have the image resolution at 300 ppi or 72 ppi. Same number of pixels, right? (The one real exception to this rule is type — text is usually measured in points in Photoshop, and that measurement is directly tied to the print size of your document. Type and text are discussed in Chapter 13.)

You can always check — or change — a picture’s resolution by choosing Photoshop Image ⇒ Image Size. Photoshop CC’s new Image Size dialog box (which you can see in Figure 2-5) offers the Fit To menu, which you can use to save and load presets for changes that you make regularly. The Resample box needs to be selected when changing pixel dimensions (otherwise you just change the image’s resolution). Next to Dimensions you can click the arrow to select a unit of measure, as you can next to Width, Height, and even Resolution. But the coolest new feature of the revamped Image Size dialog box is the preview. Position the cursor within the window and you can drag to reposition the preview and change the zoom factor. And rather than dragging and dragging and dragging in the small window to move the preview to a distant part of the image, simply click that area in the image itself to jump the preview to that location. The Reduce Noise slider can be used to minimize the amount of little speckles that sometimes appear when resampling an image.

You’ll find it very handy to change the pixel dimensions and the print size at the same time in the Image Size dialog box. And, much to the delight of math-challenged folks, the Image Size feature does most of the calculations for you. For example, with the Link option selected (note the tiny Link icon to the left of the Width and Height boxes), you enter a new Width and Photoshop calculates the new Height automatically! To disable this option so that you can change only the width or the height (which is rare), just click the Link icon.

Changing the size of your artwork with the Image Size command

You have a number of ways to change the size of your photos and other art. In Chapter 4, I introduce you to cropping (chopping off part of the artwork to make it fit a certain size or to improve its overall appearance and impact). You can also use Photoshop’s Image Size command to change the image dimensions or printing instructions without altering the composition, which is the visual arrangement of the image or artwork. All the content of the original image is there, just at a different size. Of course, as you can see in Figure 2-6, if you reduce the size of an image too much, some of that original content can become virtually unrecognizable.

If you know the specific pixel dimensions that you need for the final image — say for a web page — you can simply type a new number in the Width or Height fields in the Image Size dialog box and click OK. Of course, you probably want a little more control over the process, don’t you? Figure 2-7 gives you a closer look at the resampling options in the Image Size dialog box, with suggestions on when to use each.

If you’re resizing an image that uses layer styles (see Chapter 12), you want to click the gear button in the upper-right corner of the Image Size dialog box and make sure that the Scale Styles check box is selected to preserve the image’s appearance as it shrinks or grows. In a nutshell, layer styles (such as shadows, glows, and bevels) are applied to a layer at a specific size. You can scale the image without changing those sizes, or you can scale the image and change the style sizes proportionally. Not scaling layer styles can dramatically alter the appearance of a resized image, as you can see in Figure 2-8. A slight bevel combined with a small drop shadow produces a subtle 3D effect in the original (upper) image. Below, when the image is scaled down to ¼ the original size without scaling the effects, your chips change to chumps, and the artwork is ruined.

The link to the left of Width and Height should almost always remain selected. Some exceptions might come up, but you normally want to preserve an image’s aspect ratio (the relationship between height and width) when resizing to prevent distorting the image. Figure 2-9 shows you what can happen when you scale one dimension without constraining the image’s proportions.

The Resample option is the one that might require the attention of that gray matter within your skull. Not only do you need to decide whether you want to resample the image (change its pixel dimensions), but you also need to decide how you want to resample. Refer to Figure 2-7 to see that you have seven different ways to calculate the change (called resampling algorithms).

When you deselect the Resample option (as shown in Figure 2-10), you’re changing the print dimensions without changing the pixel dimensions of the image.

When using Image Size without resampling, you’re simply changing the instructions recorded in the image for your printing device. When you enter one dimension, either width or height, Photoshop does the math and fills in both the other dimension and the new resolution.

Take a look at Figure 2-11. I selected the Resample Image check box and entered 10 and inches for my new print width to print this image to a letter-size (8.5 x 11 inches) sheet of paper. Photoshop fills in the new height (6.667 inches). But what if I want an 8x10 print? If I enter 8 and inches for the height, Photoshop recalculates the width to 12 inches. If I want a true 8 x 10, I have to crop some of the image because most digital photos have a different aspect ratio than an 8 x 10. (You can read more about that in Chapter 4.)

Okay then, back to the subject of resampling! When you resample an image (change the pixel dimensions), Photoshop takes the image and maps it to the new size, attempting to preserve the image’s appearances as much as possible at the new size, using the new number of pixels. Of course, if you take an image that’s more than 3,000 pixels wide and resample it to 300 pixels wide, you’re going to lose some of the detail. And, conversely, resampling an image from 300 pixels wide to 3,000 pixels wide, even when using the Preserve Details resampling algorithm, is likely to introduce some softness to the image’s appearance.

Picking an image resolution

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 one-third of the printer’s rated resolution. However, most printers don’t need an image resolution higher than 300 ppi. (For fine art prints from my high-end Epson printers, I use an image resolution of 360 ppi.)

  If you’re printing something that will only be viewed at a distance, such as a banner to be hung above the crowd or a poster that hangs on a wall, you can print at a substantially lower resolution to save ink and print faster. Banners, for example, can often be printed with a resolution of 100 ppi.

• Web images: Ignore resolution (including “72 ppi”). 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. Remember, too, that some social media have specific guidelines for images uploaded to their sites. Check the site’s info before changing the image 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.)
• Presentation programs 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.

Formats for digital photos

If you print your images yourself at home or the office, you can stick with the PSD Photoshop format when saving. (Remember that you cannot re-save in a Raw format after opening in Photoshop.) If you send the photos to the local camera shop (or discount store) for printing, stick with JPEG — or, if the folks doing the printing accept it, TIFF. Here are the pros and cons of the major formats that you should consider for photos when saving:

• 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 (400MB 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 for printing. Layered TIFF files generally are compatible only with programs in the Creative Cloud. The TIFF Options dialog box is shown in Figure 2-14.

• 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, uploading to most social media sites, 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.”

• JPS: Jpeg Stereo is used to create steroscopic images that use the left half as one copy and the right half as another. It’s a specialty format for creating 3D-looking photos. You may or may not ever use the file format, but who knows what’s right down the road? (Remember the “old days” when only a few cameras could capture Raw and when nobody knew what HDR stood for? Check out Chapter 7 for info on Raw and Chapter 20 for info on HDR.)
• 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. (Either Adobe Reader or the Mac’s Preview, which you can also 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 — more than 30,000 pixels wide or long or both — must be saved in the PSB or TIFF file formats. 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 (never Photoshop Raw), but there’s no real need with the more common and more versatile formats about which you just read.

The JPEG file format doesn’t support 16-bit color, but even when working with a 16-bit image (perhaps a Raw image from your digital camera), JPEG is available as a file format in Photoshop’s Save As dialog box. The image is automatically converted to 8-bit color. It’s more convenient — saving you a trip to the Image ⇒ Mode menu to select 8-Bits/Channel — but the JPEG Options dialog box won’t give you an estimate of the file size. Don’t forget to save in a format that supports 16-bit color, such as PSD or TIFF, before creating the JPEG copy.

Formats for web graphics

Generally speaking, you use Photoshop’s Save As to generate copies of your images for use on a website or to show off with smartphones, PDAs, and other such devices. You can, however, choose File ⇒ Export ⇒ Save for Web (Legacy) if you prefer the old command. Here are the three file formats that you need for the web:

• JPG: Use JPEG for photos. Remember to resize the photo so that it fits on a web page. When selecting a Quality setting, you need to balance image appearance with file size. A smaller file downloads (and displays in a web browser) faster, but a larger file generally looks better. If you reduce the Quality setting until just before the image doesn’t look great, you’ve hit the sweet spot — the compromise between file size and image quality.
• GIF: GIF is more appropriate for items like web banners and buttons (such as those shown in Figure 2-15) than it is for photos. If you save a photo that’s more than perhaps 100x100 pixels in size, you might see some degradation of the image quality as similar colors become one color. When you save an image as GIF, it can contain no more than 256 distinct colors. JPEG and the other common file formats can have thousands of different colors.
• PNG: PNG comes in two types: PNG-8 (which is a substitute for GIF) and PNG-24 (which is a substitute for JPEG). PNG has a couple of advantages for web designers, such as support for transparency.

Formats for commercial printing

You’re the Photoshop master of your office. Everyone knows that you understand everything about digital images. So you’re the right person to create the company’s new brochure. Except you’re a photographer. Or you’re a web designer. Or you’re actually pretty new to Photoshop. And you don’t have a clue about preparing images for a commercial printing press.

Here’s what you need to know about file formats for those CMYK (cyan/magenta/yellow/black) color images that you’re sending to the print shop:

• TIFF: TIFF is generally a solid choice. Use TIFF for photographic images that don’t contain any type layers.

• EPS: Choose EPS if your image has type. Don’t flatten or merge the type layers before using Save As to create the EPS. In the EPS Options dialog box, make sure to select the Include Vector Data check box to ensure that your type prints perfectly.

  If you reopen an EPS file in Photoshop, your type layers get merged. Don’t! Instead, make sure to save your original file as PSD and, should you need to make changes, open the PSD and create a new EPS file when you’re done editing.

• PDF: PDF offers support for spot color channels, alpha channels, and paths — options not supported by EPS. (Spot channels are used with custom colors, and alpha channels store information about transparency in the image.) If your file uses any of these features, choose PDF over EPS, if your print shop accepts PDFs. When saving as PDF, the PDF Options dialog box offers Preserve Photoshop Editing Capabilities. If you select the option, the PDF file reopens in Photoshop with layers and editable type.
• PSD: Use PSD only if you’re adding the image file to a project in Adobe InDesign CC. Don’t send PSD files to a print shop unless specifically requested to do so by the print shop.

Formats for PowerPoint and Word

If the final destination of your image is PowerPoint or Word, use the PNG file format. If your image has areas of transparency in it, PNG is definitely the way to go. (Read about the two types of PNG files in the section “Formats for web graphics,” earlier in this chapter.)

What about all that neat clip art that you have on your hard drive? How do you use those images when Photoshop won’t open the vector-based WMF and EMF clip art files? Here’s how you get clip art into Photoshop, quick and easy:

1. Open a new document in Word (or a comparable word-processing program).

2. Add the clip art.

   In Word, choose Insert ⇒ Picture ⇒ Clip Art (or your word processor’s comparable command). Click directly on the artwork and drag the lower-right corner to resize it to the dimensions that you need in Photoshop. (The artwork comes into Photoshop at 300 ppi.)

3. Choose Edit ⇒ Copy.

   The selected image is copied to the Clipboard (the computer’s memory) in Word.

4. Switch to your Photoshop image.

5. Choose Edit ⇒ Paste.

   You have your clip art, ready to use in Photoshop! Use the Edit ⇒ Transform commands to scale, rotate, and otherwise fit the clip art into your design. (See Figure 2-16.)