Whats the +/- button in the Viewport?

Dondec

Anybody know what the little +/- button is next to and left of the viewport display options.

Interactive Help doesn't recognize it and I can't seem to find any info about in the docs.

Thanks

    - Don

Fishtales

Clicking on it and then on an area of the image will set the Tone Mapping for that area. If dark it will lighten; if light it will darken. You can then go to Tone Mapping to balance the image. In other words it sets the exposure value based on the area of the image clicked on.