Brand new Zbrush user, so please forgive the newb question.
I see at the bottom of the alphas panel the option to ‘import’ an alpha, and the help file there implies that one can load in an alpha from an image file. I created a test grayscale image file, 512x512 pixels, 16-bit .tif.
When I attempt to import that image file as a new alpha I get the error message: “Unable to read the specified file”.
What am I missing/doing wrong? Are .tif files not an allowed format?
Thanks!
Dan
Try a .jpg, .bmp or even a .psd (no layers in the .psd though you can crash zbrush or at least it used to crash with layered .psd files)
Not sure why zbrush won’t read .tif as I tried to open one as well and got the same message, but easy workaround is just use another format. .bmp has never let me down.
Here try this one. For a generally more effective affect import this then go into the alpha tab and invert it. And then try it with a bit of blur. Note- I made this in filter forge with a filter of my own design. So you can use it in your artwork with no worries. 
Thanks! It does appear that my problem was the .tif format. I saved the image file as a .bmp and all worked as I was expecting it to.
What I was doing was trying to load in a lunar crater bump map in order to add some detail texture an asteroid shape model. With the import alpha image problem solved it worked like a charm!
Dan