Orion 52084 instruction manual Screen Stretch Window

Number of pixels at brightness level

Figure 9. A histogram is a visual representation of the range and

Range of brightness levels levels of brightness in an image.

Screen Stretch Window

The function of the Screen Stretch Window (Figure 8) is to properly map the image brightness levels captured by the camera into corresponding image brightness levels on the computer screen. A typical camera image has each pixel (light detecting site, over six million pixels form a single StarShoot Pro image) represented as a number (from 1 to 65535) depending on brightness. This has to be mapped into the video monitor’s brightness range (from 1 to 255). It is important to set the screen stretch appropriately, or a great image may look terrible!

When an image is displayed, you will notice a graph in the Screen Stretch Window. This is called the “histogram” of the currently displayed image (Figure 9). A histogram is a simple bar graph that shows the range of brightness in an image. Each bar in the graph represents a level of brightness; the bar to the far left in the histogram represents the dimmest pixels, and the bar to the far right is for the brightest pixels. The height of the bar is the total number of pixels at that brightness level in the image. Every image has a different histo- gram depending on how much of the image is bright or dark. Directly viewing the histogram of your image in the Screen Stretch Window provides an easy interface for making decisions on how the screen stretch should be set.

In Maxim DL Essentials, the two parameters entered in the Screen Stretch Window are Minimum and Maximum. A pixel that is at the Minimum value is set to zero (black), and a pixel at the Maximum value is set to 255 (white). An easy way to adjust the Maximum and Minimum values is to move the slider arrows located directly under the histogram of the image in the Screen Stretch Window. The red slider arrow corresponds to the Minimum value and the green arrow corresponds to the Maximum value. Simply left-click and then drag each arrow to adjust it to the desired level. The best results are obtained by adjusting the arrows (numbers) until the most pleasing display appears.

There are also seven automatic settings in the Screen Stretch Window. Typically, Medium will give good results for deep sky objects, so the default screen stretch setting is Medium. Instead of using the Screen Stretch Window, it is faster to use the Quick Stretch facility. This allows you to modify the image appearance instantly with small up/down and left/right movements

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