Engraving Raster Images

Applies to: all AEON CO2 lasers

This guide explains what a raster image is and what to consider when you engrave a photorealistic image with your laser. Use it as a reference for the basics of photo engraving.

What you need

• Computer with LightBurn
• Image to engrave
• Material to engrave

Video

What is a raster image?

A raster image, also called a bitmap, is a digital image made of a grid of individual pixels. Each pixel has its own color, and together they form the picture. The common file formats are JPEG and PNG, and those are the ones you will most often see when engraving an image.

Raster images are resolution dependent, so resizing affects their quality. Enlarging one loses sharpness and detail, and shrinking one can lose information.

Pick an image

First decide whether the image can simply be converted into a vector in LightBurn. An image like the one below could be run as a raster, but the results are better if you convert it to a vector first. Converting also gives you the standard options in the Cuts/Layers window, so the file runs as normal. See LightBurn’s video on the trace feature for the best way to convert an image like this.

Next consider image quality. A good, high-resolution image makes a world of difference. The better the photo, the easier it is for the software to create shading and depth, a process called dithering. A photo that is poorly lit or out of focus will not dither well, and a low quality image gives a low quality engrave.

An image like the one below is better run as a raster, and its quality should give a good result. Fine detail and subtle shadows come through better without tracing. The photo is good quality and in focus.

Edit the image

Once you have a suitable image, it needs processing. LightBurn can do this itself, but an external editor such as Photoshop is often easier and gives better results. For this guide, all the editing was done on the phone that took the picture.

First change the photo to grayscale. LightBurn imports the image this way regardless.

Then crop the image. The more background you remove, the better. Extra background adds job time, and detail can be lost because it changes the overall balance of the image. Many modern editors can trace the outline of the part you want. The example below shows the background cut out (left) and left in (right).

Any background you leave in will be engraved. If you want it, leave it, but you will need to fine-tune the settings so the whole image engraves properly.

Photo editing is a visual process, and the best values are a matter of judgment. Adjust these four settings, which make the biggest difference:

• Contrast
• Brightness
• Gamma
• Sharpness

You can also adjust highlights, shadows and tone. The goal is an image that looks as crisp as possible, with solid contrast and clear definition from light to dark.

When the editing is done, save the image and import it into LightBurn.

Create the file in LightBurn

Import the edited image into LightBurn and open the Adjust Image menu.

The main controls are at the bottom of the window.

Image mode

There are several modes, each with its own use. Experiment and pick the one that looks best to you. The most common are Stucki and Jarvis, which are the most likely to reproduce the imported image. This guide uses Stucki.

Negative image and DPI

Whether to make the image negative depends on the result you want and on the material. A material that darkens when lasered, such as wood, usually needs no change, because the dark and light areas already land in the right places. A material that turns lighter than its original color, such as slate, needs a negative image to put them in the right places. This guide uses slate, so the image was made negative.

DPI depends heavily on the material and the finish you want. Run tests at different DPIs to see what works best. This guide uses a DPI of 318.

Contrast, brightness and gamma

These work the same way as in any image editor.

Enhance radius and enhance amount

These two settings work together to sharpen the edges in the image. Amount is the strength of the effect, and radius is the area it covers. The setting is easiest to understand by eye, so compare the example images below.

Adjust them to see what works best for you. This guide uses a radius of 25 and an amount of 100.

File settings

The settings depend on the material, the tube wattage and more. Run tests on a scrap piece to see how the file comes out. This guide used slate and a 60 W CO2 tube, with the settings below.

The most important settings here are speed and power. We kept both at the lower end, with a large difference between minimum and maximum power.

A large power gradient lets the machine add shading. Sparsely dotted areas get less energy, and densely dotted areas get more. On slate, the engraved areas turn light and the untouched areas stay the dark slate color.

Two ways to test

• Shrink the whole image and run a small version. This gives a miniature of the full job to judge. Be careful: shrinking the image effectively raises the DPI, so areas that would be lightly engraved at full size get more energy. You may need to adjust the power or other settings to compensate.
• Run a small portion at full scale. The dot density matches the final job, so the test looks like the finished piece. The drawback is choosing a portion that represents the full range of dot densities in the image. A setting can look right on the test while another area, such as the nose, ends up too dark and washed out.

Run the job

With the file created and the tests done, run the file. There is usually no need to change the machine setup. Place the material in the center, then set the origin and frame as usual. If all goes to plan, the result should look something like this:

Learning what each settings change looks like on the material takes time, but with patience the results are well worth it.