When creating a halftone in Photoshop the layer locks?

At the moment i am trying to create a halftone in photoshop.


When i first open the image it's full color %26amp; the layer is unlocked.


Then i change the image to grey scale, then to Bitmap.


In Bitmap i choose the frequency %26amp; once i click okay the layer locks.





How do i unlock the layer so i can make some more changes?When creating a halftone in Photoshop the layer locks?
Bitmap mode does not support working in layers - so you must temporarily switch back to one that does, such as grayscale or RGB, for example.