Image positioning

From the discussion above, it follows that the incoming image should follow the DMD resolution as much as possible to reduce latency. If this is not possible, the image should be adjusted and positioned as close to the bottom edge (in desktop-front projection mode) of the DMD as possible to have minimum latency.

To position the image on the DMD, it’s recommended that the digital image shift is used. This function shifts the image content and is done after the image has been warped. Shifting the image does not degrade pixel quality and no scaling is used for this functionality.

Another option is to use the warp settings itself, either the 4-corner coordinates of the warp mask or the warp grid calculated externally. Always adjust the warp grid to position it as close to the bottom of the image as possible.

A curious effect of this is when applying keystone warp to an image smaller than DMD resolution and the output is adjusted down as discussed above. In the following example some keystone (4-corner adjustment) is applied.

In this setup, the projector latency will in fact be lower than the uncorrected image. This is because the output image has fewer active lines than the incoming image. All the incoming lines are used in the warp calculations, but the resulting image consists of fewer active lines than the original. The projector can take advantage of this by preloading the DMD with black lines before the actual content. Note that for a 60Hz system, latency will never go below 16.66667ms because the DMD is displaying the image synchronously with the refresh of the incoming image.