Coming up with the right resolution for an image can be tricky, especially when you are not yet sure how you intend to output your image. Print files need lots of pixel information, or detail (i.e., 266-300 ppi), while files intended for e-mail or posting on a web page can get away with a whole lot less (i.e., 72 ppi).
Knowing that Photoshop is really good at throwing away extra pixels (downsampling), but not so good at adding new ones (upsampling), most of us set our digital cameras to their highest possible resolution, for maximum flexibility.
So how come the files say that they are just 72 ppi (pixels per inch) when you open them up for the first time? The key is learning to understand the Image > Image Size dialog box. Here's how the dialog box looks when I open up an image freshly transferred from my camera:
Yes, the dialog box indicates my file is just 72 ppi, but take a look at the document width and height: 45.333 inches by 34 inches! To figure out how large I can print it, I do two things:
- Deselect the Resample Image checkbox.
- Change the resolution to 300 ppi.
With Resample Image off, I keep the exact same number of pixels in the image, but they become smaller when I increase the resolution. This dialog box tells me I can print anything up to an 8" x 10" with this camera (with a little room for cropping).
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About the author: Barbara Binder is the president and founder of Rocky Mountain Training. Barbara has been a trainer for nearly two decades and has been recognized by Adobe as one of the top trainers in the world.