Set the resolution of the rendered image by specifying the width and the height of the image, in pixels.
There are three resolution settings that control how a rendered image appears; the width, the height, and the image aspect ratio.
Setting Width and Height
The width and height settings control the size of the rendered image, measured in pixels. A pixel (short for Picture Element) is a single point in a graphic image.
The default output resolution is 640 x 480 and can be set as high as 4,096 x 4,096. Higher resolution settings result in smaller pixels and finer detail. High resolution images also take longer to render.
Output resolutions that are set in the Output Size dialog box are saved with the current drawing and displayed on the Render Output Size list on the Render panel of the ribbon. To test the rendering, use lower resolution settings (320 x 200 or lower). As you add detail and materials, shift to mid-range settings, such as 640 x 480. The final presentation rendering should use the highest resolution required by the project (1024 x 768 or greater).
Setting Aspect Ratio
Aspect ratio describes the proportions of the rendering, expressed as the ratio of width to height, regardless of the image's resolution. The aspect ratio is controlled by the Image Aspect setting. Aspect ratio is usually expressed either as a ratio of width over height (for example, 4:3) or as a multiplier (such as, 1.333). Changing this value changes the Height value to maintain the correct dimensions for the output resolution.
The following example shows various aspect ratios.
If you lock the image aspect, the width and height are tied together; changing one automatically changes the other while maintaining the aspect ratio.