Sometimes dragging a cursor to select a portion of your screen to capture doesn't cut it. If your work demands screenshots that are sized just right, and you are on a Mac, take Precise Screenshot out for a spin. This $1.99 app lets you save preset sizes among other convenient controls.
When you launch the app, it places a small icon in your menu bar and opens three windows: a red framed capture area, a control panel, and a small preview window. You can drag the sides or corners of the red frame to resize the capture area, or you can use the up and down arrows on the control panel to make finer corrections to the capture area. The arrows are located to the right of the Size pull-down menu. The left set of arrows adjusts the width; the right set adjusts the height. Click the plus sign just to the left to save your current sized window as a preset (use the minus button to remove a size from the list of presets.)
At the top of the control panel, you can to capture a frame or the entire screen. Just below, you can choose to capture a screenshot immediately when you click the Get Screenshot button or use a timer. The timer is set to 5 seconds by default, but you can anywhere between 0 and 10 seconds.
You can save screenshots to the clipboard or to a specific folder on your Mac. Screenshots can be saved as one of three formats: PNG, JPEG, TIFF. At the bottom of Precise Screenshot's control panel, you can choose a naming and numbering convention for your screenshots.