Focus Panel
This digital camera system provides an extremely accurate method of verifying correct image focus after the device has been inserted into the view camera.
Focus can be checked and adjusted at any point in the image, using data from the CCD image sensor itself.
While this method is no substitute for proper setup of the view camera’s tilts and swings before installing the insert, it can later compensate for any camera “sag” caused by the weight of the insert, or for any error between the position of the ground glass and that of the CCD image
sensor. | Focus tab panel with only the green channel in use. |
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Since digital focus verification is done at the working aperture for the scan, any focus shift caused when stopping down the lens can also be eliminated.
To utilize digital focus verification, first take a prescan of the subject, preferably with a reasonably proper exposure and approximate focus. After any prescan, click on the Focus tab panel, located on the main control window. After entering this panel, indicate where the CCD should be positioned by clicking in the appropriate location in the preview image area. A small rectangle will appear as a marker at the selected location (this marker can be repositioned as necessary by simply clicking in the
new location). After a location has been marked, click the 
button in the Focus tab panel. This will position the CCD at the indicated location, and begin displaying focus information. Focus data is displayed in both graphic and numeric form; by rocking the view camera’s focus adjustment, the best focus can quickly be determined. This system is so accurate that in many cases, it is possible to selectively focus on each color in turn, and in subsequent scans demonstrate that the selected color is indeed sharpest (even when using apochromatic lenses). After focus has been verified at one or more
sites, click the 
button or click on any other tab panel to end the focusing task and return to normal operation.
Large Focus Display
To aid in using the Focus panel at a distance from the computer screen, click on the Zoom button. This will cause a large graph display to appear. The same information present on the small graphs
in the Tone panel will be shown in the large display window. Clicking the Stop button will close the zoomed focus window.
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