Carve the pumpkin and take a photo of you and your pumpkin. Also the pumpkin does not fit in the laser and keep the focal length. So I cut the face off the pumpkin at an angle so it could be reattached using toothpicks after it has been etched.
Prep the image in photo editing software, in my case i will be using Photoshop. Open image convert to grayscale. Adjust contrast to optimize image when laser etching, you will want to make sure to adjust to optimize highlights and shadows. Preferred image for laser software is bitmap. Save file as bitmap.
Open image in to laser engraving software, In my case using Retina Engrave by Full Spectrum laser. I'm going to use the threshold setting in the software to etch separate layers and ad depth to the etching. I will also invert the image to the highlights get etched. Because the pumpkin will be lit from the inside we want the highlights to be deeper so they show up lighter giving the etched image depth. I start with a threshold setting of 0.05. This is the first layer and it barely etches the skin of the pumpkin. Settings on the laser are cut speed of 100% and laser power of 5%. Repeat the steps stepping up the threshold by 0.10 every pass. Example second etching is done at 0.15. The amount of etching will narrow with each pass cutting deeper and therefore let more light through allowing the contrast so show. I went up to 0.65 for the threshold setting giving me 6 layers of etching.
At this point the etched pumpkin will not look correct to the eye without backlight. Using toothpick re attach face of you pumpkin and add lighting source inside pumpkin. This backlight should illuminate your layers at different levels and show highlights and shadows.