Sony MSW-900 Operation Manual page 152

To reduce the influence to the auto iris due to shooting a high
luminance subject
When shooting a high luminance subject, the auto iris closes too much
and a white crush may occur on the image. In such a case, you can
reduce the influence to the auto iris by setting CLIP HIGH LIGHT to
ON on the AUTO IRIS page of the USER menu.
Since the level exceeding a certain level is clipped, the influence to the
auto iris is reduced.
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Chapter 4 Adjustments and Settings for Recording