If you ever save an image, and you find when you view it on the Macintosh, outside of Photoshop, outside of Bridge, that the preview thumbnail image looks weird, it's either completely empty, or it only shows part of your image, then what it means is you have an image that has a channel in it. If you make a selection, let's say like this, you go to the Select menu and choose Save Selection, the place where it saves that selection is known as the Channels panel. And so if I go to Channels, you can see it sitting right there. And in certain file formats, the Macintosh operating system will take whatever is in that channel and think that it should tell it what should be visible or not. And any part that is black would become hidden. And so if you ever find that you saved some files and on the Mac operating system, the thumbnail images are just missing a bunch of information, it means the first channel in your document contains a lotta black. How would I fix it? Create a brand-new channel.
Just go to the Channels panel, hit the little plus sign at the bottom, and make sure that whatever channel it is is full of white. So I could go over here and choose Invert to get it to be full of white and make it so it is the first channel. And then just re-save the file, because the Mac operating system has a preference in looking at whatever the first channel is, what's called an alpha channel, and having that be used to determine what should be visible versus hidden. So if we put a white channel there, white means show up, and therefore, it should fix it and make everything show up. So there are all sorts of problems you can encounter when working in Photoshop. One of the main things is they're selection active, what's selected in the Layers panel as far as what type of layer, that kinda thing. But by going through this particular lesson and reviewing the handbook that comes along with it, if you purchased it, I think you'll be able to be, be able to troubleshoot much of the problems you'll encounter in Photoshop.