Image tracing presets

Select the source artwork and select the Auto-Color Preset to trace them. Often you get a result where there's not much left to adjust. 

To further adjust the result, you should check how exact the paths follow the source. Press and hold the View Source button to switch temporarily to the source image to identify the areas that need improvement. Notice that the trace result always moves slightly down and to the right. This can’t be corrected. 

In the Image Trace panel’s Info area, you should also check how many different colors have been created. Does that match the number of colors in the source image

Next, open the Advanced area by clicking on the little arrow to the left. To get a more detailed result, move the Paths slider to the right. Note that paths might also get more bumpy then. 

To get sharp corners, move the slider Corners to the right. With the slider, you define that you prefer corner points even if the angles in the source file are not too sharp (note the left inner part of the bone). 

Note that once you change the options from what was originally set up, the menu listing in the "Presets" menu changes to "Custom".

To get rid of small shapes or dust from a bad scan, move the slider Noise to the right. With this slider, you specify the minimum number of neighboring identically colored pixels that are traced as a shape.

Start off with the Black and White Preset. Press the View Source button to check the result. 

To further adjust the trace, use the Threshold slider to darken resp. lighten the result. Moving the slider to the right get you the lighter strokes, but sacrifice the detail in the areas that are already dark. With this image it’s difficult, because you want to have both the slight black strokes and the tiny white details.

Use the Noise slider to try and catch some more of the intricate detail.

To balance the smoothness of the paths against the accuracy of the trace, adjust the Paths slider. 

Check the Ignore White box, so that Illustrator only generates black shapes and you can create a brush out of this right away after expanding.

Start off with the Black and White Preset. Press the View Source button to check the result. 

Adjust the Threshold to balance the dark and light areas. 

Now it’s also important to reduce the amount of detail by adjusting the Noise slider. Especially when you want to actually get this vinyl-printed on a T-shirt. 

Afterwards adjust the Paths slider to control the smoothness of curves. Usually you want to make them smoother.

Using the Corners slider you could try to get nicer curves by decreasing the number of corners.

Check the Ignore White option to only generate black shapes. 

To get a photorealistic autotrace, start with the High Color Preset. In the Info section, notice that your trace has thousands of colors.

To improve the result, try to get even smoother color blending by increasing the number of colors: move the Colors slider to the right. 

As in almost any trace you also need to balance detail and smoothness by using the Paths slider.

The preset has a low Noise value thus tracing a lot of small detail. Increasing it might cause some abstraction of your image, so this option needs to be treated with caution.

Start off with the Low Color Preset. It vectorizes the photo using a limited number of colors. 

You can further decrease the number of colors by using the Colors slider. When doing so, you actually determine the number of colors you want to have in the result. You can check in the Info section that the number of colors matches your input.

Next reduce the accuracy of the trace by moving the Paths slider to the left. 

Also reduce the amount of detail by increasing the Noise value.

Next comes the fun part: applying different colors to the artwork. To do so, open a swatches library that contains the colors you want applied, e.g. by selecting it from the Swatch Libraries menu in the Swatches panel. The library needs to be open. 

Then in the Image Trace panel you can select your library from the Palette menu. Illustrator assigns the colors from the library to the original colors by its own algorithms – you don’t have an influence on that.

In case your library contains a number of color groups, you can select one of them from the Colors menu.

If you want to assign colors differently, you need to Expand the Image Trace and then use the Recolor Artwork function to exchange colors. 

Start off with the Auto-Color Preset.

The goal must now be to unite as many of the gradient colors as possible, because this gives you smoother paths and causes therefore less work than editing afterwards. Try and move the Colors slider to the left to reduce the number of colors.

When done with optimization, you need to Expand the Image Trace and apply a gradient to the shapes.

Start off with the Outline Preset.

It creates a completely different trace than the other Presets by tracing not with shapes, but with strokes. You can check that by selecting Outlines with Source image from the View menu. 

To further adjust the result, check the option Snap Curves to Lines.

You should also try out if increasing the Corners value improves the result. 

Again you start off with the Auto-Color Preset.

The result needs a lot of adjusting. Start off with the Noise slider and decrease the value. Then increase the accuracy of the Paths. Don’t move it to the far right, because paths get bumpy then.

The trace still needs some editing, which most likely can only be done manually. To prepare this, you need to change the Method to Overlapping. This creates stacked shapes where possible. If it’s not possible to stack them, Illustrator at least overlaps their edges.