DPI vs. Resolution

One misperception we hear time and time again is about resolution. For the record, video graphics are not 72 dpi. First off, dpi stands for dots per inch (as in printing). Photoshop measures graphics using pixels per inch (ppi).

The resolution of this photo has been reassigned from 300 ppi to 72 ppi. The Document Size (in inches) has changed for printed output. The pixel dimensions and file size remain unchanged at 1920 x 1080 pixels (for a 1080 HD video project).

When dealing with video graphics, resolution doesn't matter. The same HD video file can play back on a laptop, a television, or on a digital projector, and the total number of pixels won't change. To see this clearly, stand really close to a big-screen HD TV; the picture looks soft. Now find a smaller display with an HD signal; the picture looks clearer. This is because HD is HD; the bigger the screen the larger each pixel is displayed, but again resolution doesn't change.

Figure 9.2 The enlarged area shows the individual pixels that make up the butterfly image.

Setting Photoshop to Measure in Pixels
Out of the box, Photoshop is set up for a print workflow (biased isn't it?). This is easy to fix with a simple preference change. You can set rulers and other tools to measure using pixels by default (which will make designing for the video screen easy).

  1. Launch Adobe Photoshop.
  2. Press Command+K to call up your Photoshop preferences.
  3. Click the Units & Rulers preference tab.
  4. Click the Rulers menu and set it to pixels.