This page contains charts of the size of a 16-inch Siemens Star on the camera sensor with the camera at the minimum focusing distance. By that I mean the minimum required camera-to-target distance that provides enough depth of field so that there is acceptable defocus blur with the target at the corners of the image when a 51 megapixel medium format camera with a 33×44 mm sensor focused with the target centered. In the case of these charts, the acceptable circle of confusion (CoC) is defined to be one-half the camera’s pixel pitch.
The size of the target is measured in pixels. At least 100 pixels is required for good results. 150 is better. If the focal length and aperture combination that you wish to employ will result in too small an on-sensor target size, you will need to print a larger target. For example, if a 16-inch target will be 70 pixels, you’ll need a target that is at least 16 * (100/70), or 23 inches, and optimally 16 * (150/70), or 35 inches.
There are three charts, with the lens focal lengths getting larger as one proceeds further down the page. Once you find the chart that’s appropriate to you, click on it. Then click on the image that you see next. That will get you the full-resolution version of the chart, and you can copy it to your computer, or print it.