Engraving a Photograph on Acrylic
PhotoGrav software helps process images for engraving.
Achieving a quality engraving of a photograph on cast acrylic
not only is less complicated than ever and the results vibrant and dramatic, it
gives awards retailers more in their product offerings to wow their clients.
Proper software is a key ingredient to making the image
first-class.
But even before you create the artwork and send it to your laser engraver, you
need to understand that not all acrylic-type materials are manufactured the
same: There are two primary types of acrylic on the market for laser engravers,
namely “cast” and “extruded.” They are given these names due to the technique
used in the manufacturing process of these respective types of material. The
acrylic material type that we find most responsive to photographic detail is the
cast variety.
Once you have selected a piece of cast acrylic and the image
you want to engrave, you are set to begin the process of engraving the photo.
Using PhotoGrav software to help process the image for the
engraving, I have outlined the five basic steps to follow:
RESAMPLE
Perform any necessary preprocessing touch-up to the image such as jpeg artifact
or halftone correction, contrast, brightness, etc. using photo-editing software
of your choice (e.g., Adobe PhotoShop, Corel PhotoPaint, etc). You also want to
resize or resample the image to the desired dimensions and resolution (dpi). I
suggest resampling the image to exactly one-half or the same resolution that you
will be engraving. For example if you prefer to engrave at 500 dpi, then
resample your image to 250 or 500 dpi as well. This resampling can be done
directly in PhotoGrav 3.0 and above.
BACKGROUND CHECK
Next for any “negative” type material such as acrylic, make
sure the background of the image is all black (not white) if the background is
not to be engraved. This can be done by selecting or masking out the background
of the image by using a simple painting tool such as the familiar “paint bucket”
to paint the background black. Sometimes the image to be engraved leans toward
the darker colors. If this should happen you will most likely want to lighten up
the engraved part of the image a fair amount to provide a nice contrast to the
now-painted black background. It should be noted here that PhotoGrav does not
require the background to be removed; it will usually perform quite well even
with the background not removed [See included photos].
BIT BY BIT
With PhotoGrav 3.0 or later you can open up the image, either
color or grayscale, directly into a PhotoGrav “Session” in the images native
format if it is one of the supported file formats (jpg, tif, bmp, png).
However, for version 2.11 and earlier you must convert the
image to an 8-bit grayscale and either Export or Save As a Windows bitmap (.bmp)
type of file, again using your favorite image-editing software. Be sure that the
type of .bmp file selected in the Export or Save As dialog is a Windows type
bitmap as opposed to an OS/2 bitmap type. Also, be sure to save the image with
no compression of any kind, whether LZW, RLE, etc. In some Save As or Export
dialog windows it will ask you to select the number of bits you want to use; of
course, make sure that the 8-bit option is selected.
SAVE TO ‘ENGRAVED’
If using version 2.x open the saved .bmp in PhotoGrav. Once
the image is opened select the material in all versions of PhotoGrav for “Clear
Acrylic (cast type)” or “Black Painted Acrylic,” and press OK. Then select the
“Auto Process” button and let PhotoGrav do its job. You now will be able to
cycle between four (three in ver 2.x) images, namely the Simulated, Engraved,
Grayscale, and the Original. You will want to save the Engraved image with an
appropriate name and to the appropriate directory for your project. The engraved
image will look somewhat strange, but don’t worry; it is optimized for laser
engravers. So, just ignore the graininess of the image.
ENGRAVE
The last step is to open up or import, the “Engraved” into
the software that you use to perform the actual engraving (CorelDRAW is
preferred by many laser engravers, but sometimes they use other software or
software that comes with their laser engraving system).
Do not resize or make any adjustments to the image after it
has been processed by PhotoGrav. Note, however there is only one exception: It
is acceptable to mirror or flip the image after it has been processed by
PhotoGrav. You can choose to flip the image either in PhotoGrav or in the
software you use to engrave. Most people prefer to engrave acrylic on the back
side, which gives it more of a 3-D effect, and usually provides an overall
better appearance.
Afterward, simply import and position the image as necessary
for the acrylic material you selected and engrave the image at the appropriately
scaled speed and power settings for your laser engraver: For our 100W laser we
prefer to engrave at a resolution of 300 dpi, a speed of 90% and power at 20%.
POINTS TO CONSIDER
Summary of a few more important things you want to remember
when engraving on acrylic:
- Ensure that you purchase the “cast” type of acrylic.
- Paint the background of the image black if you don’t intend for the background to be engraved
- Flip or mirror the image after PhotoGrav has processed the image (if engraving on the back side of the acrylic piece)
- Engrave on the back side of the acrylic piece