Last week we chatted about pixels and resolution, and the importance of deciding what an image's purpose in life shall be. "To print, or not to print," that was the question. This week, I'll show you how to navigate inside the Image Size dialog box, enabling you to tweak image resolution and sizes at will. Though this tutorial is done in Photoshop Elements, the steps are nearly identical in the full-blown version of Photoshop.
To illustrate how tweaking the resolution of an image affects its document or physical size, let's take a peek at resizing a web image.
From our discussion last week, you know that images on the web are lower quality than those destined for print. Knowing this, you will surely realize any attempts at printing such "virginal" web images will produce less than appealing results. The solution is to change the resolution before you print it.
For example, let's say I need to include a cover shot of David Pogue's Tiger Missing Manual in my Mac User Group's printed newsletter. After finding the book cover on the web, Control clicking it and saving the image to my desktop, here's what to do next.
Step 1: Pop open the image in Photoshop Elements, proceed immediately to the Image menu and choose Resize > Image Size.
Here's what we get:
At the top you see pixel dimensions in both width and height. Remembering our discussion from last week, this is the total number of individual dots (pixels) which make up the image. In the center you see something a bit more familiar: document size. This is the physical size of the image at the current resolution (by default it's expressed in inches). At 72 dpi, this image is a little over 3 inches in width and height. Since we know 72 dpi is going to print extremely crappily, we must change it. Read on.
Step 2: To play around with only the resolution and not the quality of the image, we need to uncheck the Resample Image option at the very bottom of the dialog box (circled in red below). Doing so will lock the number of pixels of which the image is comprised safely out of our reach. Notice below how the pixel dimensions are now grayed out.
Step 3: Let's say we're going to print a master copy of the newsletter on a home inkjet printer, and we know from last week that 225 is probably a decent resolution for printing on that particular device. Type 225 into the Resolution field and watch closely what happens to the document size.
See how the document size went from 3.33 inches to 1.067? Increasing resolution *decreased* the document size (physical size) when the Resample Image dialog box is unchecked. This is muey importante stuff to remember :)
For funsies, now type 300 into the Resolution field.
See how the physical dimensions decreased even further? The higher the resolution, the smaller the document size.
Thus, this is the little dance one does when snatching web images to print. If the image is large enough on the web, and the size you want to print the image is smaller, you can usually raise the resolution enough for it to print decently. If the image isn't quite big enough, trot over to the Upsizing an Image with Minimal Quality Loss tutorial for an emergency quick fix.
Luckily for us, a resolution of 225 produces an image roughly 1 inch square, which is fine for our newsletter. Press OK to dismiss the Image Size dialog box.
Step 5: Add a touch of class to the image by slapping a black border around it. Double-click the Background layer in the layers palette to rename it (while it's named Background, it's uneditable). Trot up to the Image menu and choose Stroke (Outline) Selection.
Step 6: Enter 1 pixel, pick black from the color well, and choose a Location of Inside. Press OK.
Step 7: Now it's time to save the image. Choose File > Save As.
Step 8: Choose TIFF from the format pop-up menu and check the As a Copy option. Press OK.
Now you have a printable, high-quality TIFF ripe for plopping into InDesign, Pages, Word, or whatever software the newsletter was created in.
Tune in next time for resizing and cropping images from digital cameras!