I was reading a chapter on layers in Illustrator. I felt like the book explained where to find different tools but did it no justice of why layers are so important.
If you are a complete beginner:
Layers are sort of like transparent sheets on which all your elements go. you can have everything on one layer, or you can have multiple (essentially infinite number of) layers. Layers can have sub-layers, groups, and paths. Sub-layers can have their own sub-layers, groups, and paths. Sort of like infinite Russian dolls. Here's an example and its hierarchy.
Now, bring up the Layers panel (F7), hover over the buttons, take a look at the menu, poke around figure stuff out, I'm not going to go into too much detail here - I strongly believe that you can figure out how to add new layers and delete them :D .
if you are not a complete beginner:
So. Layers. In Illustrator at first it seems they are not so important as you can have a bunch of elements on the same layer and can still manipulate them individually. However, when you make something complicated (and trust me you will very shortly after getting into Illustrator), you will end up with a really big list of elements and will have to scroll a lot to find what you're looking for.
So, layers and groups help with organizing and keeping you sane.
For example if I draw a person (or an animal, or an alien) the facial features are always on a sub-layer and grouped up in a way that makes sense to me (like left eye group, right eye, mouth, etc.)
More importantly keeping things on separate layers will make your workflow a lot faster and easier - because you can lock layers making them unclickable and uneditable. Or you can hide them. The locking of layers is important because if you have a bunch of paths overlapping one on top of the other you will get annoyed trying to select the correct element. A couple shortcuts and tricks that will help:
Click to Target - every layer, sub-layer, group, and path has a circle on the right to their name. Clicking on it will select all elements in that entity. This is very useful for repositioning stuff in your artwork.
Locate Object - (one of the buttons on the layer panel). This is a life-saver. Select your object with any selection tool and click that button - it will find it for you on the layers panel. Instnatly. No scrolling around.
Reverse Order - select a couple layers (they don't have to be consecutive), click on options from layers panel, and click reverse order. This is a lot faster than rearranging a bunch of layers manually by dragging them around.
Alt - Click in layer's lock column on the Layer panel - this will lock all other layers of same indentation. This is really convenient when you need to do some fine work on specific paths without anything else getting in the way. Alt-click on the same layer again to remove the locks from other layers. This works the same for visibility field (show/hide layers).
Collect in a New Layer - select a bunch of same indent elements click options on layer panel and click Collect in a New Layer. Self explanatory. Much more convenient than manually dragging it to a new layer.
Ctrl - click on Create New Layer - if you're in draw normal mode: the new layer will be the top layer; if you're in Draw Behind mode it will be the layer on the very bottom.
Layer Options (double click on a layer):
This is pretty neat - every layer has its own color for selection tool (V) bounding box. You can change the color to whatever you want. This is handy for when the selection color is close to what's on the layer - like if you have a sky background and the layer color is blue it will be hard to see.
Template and Dim Images to %: These are a great features and quite similar. They dim the layer. Template works fine but if you want to make it even more dim or if it's too dim then just check dim images to instead and enter the desired percentage. The reason why this is important: it works great for when you have a scanned sketch that you're going to use as a stencil for your illustration.
Layer use and good practice
Ok, so layers are good and all-mighty - I never work without Layers panel open - and I do mean never ever - I'd feel completely lost without it. However, don't go overboard with layers either.
If I have a couple artboards I make a separate layer for each of them and make sub-layers where necessary. If I have only one artboard then I will have different parts of the illustration on separate layers.
I almost always have a background layer - sky, grass, the view in the distance - all that goes there. You can add more stuff to it it's up to you. I prefer having a separate layer for say flowers and other details. That layer comes right after the background. That may be a couple layers. Then for each person or object in the foreground I will have a separate layer.
If it's a simple drawing I will add another layer for shading. or shading will be on sub-layers for each layer. For shading I usually use a brush, black color, then select everything on that layer and add transparency or set the visibility to overlay or multiply (Appearance panel Shift-F6). Same for highlighting.
Here's an example:
So at first I would draw all that on respective layers except shading, then painlessly reposition the girl or the trees or whatever else. Once I was happy with it I would do the shading. If I knew in the future I may want to move stuff around again I would make shading sub-layers for each layer, so that it would move around with the respective objects.
This post is based on my personal experience and my workflow - different people may see things differently and in the end there is no right or wrong. However, I myself find it most useful to see how other people in the field do things and use things and share their thoughts or experiences - it's one of the best ways to learn and get good habits. So, I hope that this will help some people out there :) But definitely don't take my word for it - go try it out yourself, mess with it, click stuff, make your own mistakes, get your own experience!
