In addition to the “waveform” graphic display, the pixel data from each line segment is analyzed by the computer, using algorithms that detect and amplify the differences in brightness between adja- cent pixels. The result from this analysis is displayed both as a number in large type, and as a bar graph. As the number increases, the bar graph will “fill in” with the color of the selected color chan- nel. If the number decreases, the bar graph color will also recede, but a different color will remain behind to indicate the maximum number that was displayed. This “peak hold” display is quite useful for establishing exact focus in most situations by simply turning the camera’s focus knob in the direc- tion that causes the number to increase (and the bar graph to advance) until a maximum is reached and the bar graph begins to recede (leaving a “peak hold” segment). Then turn the focus knob in the opposite direction until the preceding maximum is again indicated by the bar graph (again covering the “peak hold” segment). If desired, rock the focus knob through the indicated maximum display several times to verify correct focus. Use the numeric display to resolve changes smaller than the graph can display, but don’t be too concerned with very small changes. There is no ideal number. Each setup will yield a different number range based on the subject contrast, the surface texture and the tone curve selection. The objective is to maximize the numeric value.
If, during focusing, the displays appear erratic or inconsistent, the cause may be due to specular highlights and/or sharp edges moving in or out of the selected viewing segment.
This can often be confirmed by observing the “waveform” display, which may show significant, sudden spikes or steps as these features appear (usually accompanied by a big jump in the focus number and bar graph). Try moving the selection rectangle slightly to eliminate this problem by click- ing in the preview image at a new location very close to the original.
The CCD will automatically reposition itself to the new location and restart the focus dis- plays when the focus target position is changed in the preview image.
Audio Focusing Aid (Mac only)
Click on the speaker button 
on the Focus panel to turn on or off the audio focusing tool. The tone will rise in pitch as the focus is sharpened and fall in pitch as the image is defocused.
Multiple Color Focusing
The Focus panel contains a set of buttons that allow the user to select any CCD color stripe to be used for focusing. This selection is preset to the proper channel for the chosen capture mode (green, for a color image, and the selected color for a monochrome image). In most instances, it should not be necessary to change this selection, however, in certain applications it may be desirable to verify focus using a different color, or to check focus in several colors. The focus may be checked in more than one color by clicking on the associated color selector and the data for the additional channel will
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