Masking Question

[websteve]

I am creating a montage using the mask and the history brush, but sometimes when I use the brush, I get the following error message:

Could not use the history brush because the history state lacks a corresponding channel

Can someone explain what this error means?

Thanks

 

[blueark]

The history brush is often very fussy about what has been done to an image. For example, if you add a layer mask after setting the history source, the history brush will give that message if you try to use it on that mask. That's because the mask doesn't exist in the specific point in history, so it has no reference point to work from.

You can use the History palette to define how far back the history should go. Simply click to the left of the stage you want to go back to. If you're getting this message, select somewhere after the mask was created.

Incidentely, there are a few different variations on this message, such as when you change color mode or resize the image.