Hi all. I am having trouble engraving photos. The problem is, when the photo is on the computer it looks fine. When it gets engraved on the material (glass, marble, leather), it has “lines” on the photo. It’s kind of hard to explain, but if you have ever taken video using a video camera of a tv show and the screen appears to have “lines” across it when you play back the video. The annoying part is that it doesn’t happen all the time, so you never know which project it will screw up. Has anyone else had a problem similar to this? Will PhotoGrave take care of this? Anyone want to sell a copy of their copy?
Can you tell us a little bit more about how you prepare the photos for lasering, for example are you turning the photo into a halftone screen in something like Adobe photoshop or Corel photopaint? What you describe sounds like an interference pattern when the dpi of your photo and the dpi of your laser are slightly miss matched. These can be overcome by changing the dpi of your photo (usually going to a lower dpi) or the angle of the dots.
I usually scan the photo into corel draw 11, convert it to a bitmap and engrave it at 300-600 dpi. Where I have found the most problem is doing marble because I only have a 25w laser and I have to run the speed at 5-10% to get a good etching. Should I be doing something different with the photos rather than just converting them to bitmap? Thanks.
While our laser has a photo mode built into the driver, I’ve found I can get more predictable results with photos if I convert the bitmap image into a halftone screen image (like a newspaper photo made up of a lot dots). It’s actually the same process I would use to prepare a photo for sandblasting.
I’m familiar with Corel 9 & 12, so assume 11 is the same.
Select your bitmap and then on the menus go: Image > Color Mode > Black and White (1 bit) Set the conversion type to halftone, the screen type to round, the lines per inch 40 - 80 and the angle to 30 to 35 degrees. You might need to experiment with some of these settings. As an alternative you can also try the Jarvis conversion type, sometimes this gives really nice results.
I usually do one or two test runs on a piece of scrap and change the settings a bit to make sure I’m happy with the results before I commit to engraving the final piece.
One issue I’ve run across is the DPI setting in the laserpro driver isn’t the actual DPI of the machine. For example, 250 DPI (dots per inch) is actually 100 DPC (Dots per centimeter) which equal to about 254 DPI. When a 250 DPI bitmap was sent to what i thought was a 250 DPI laser, the results was a subtle off shade bands punctuated with a hard line every 1/2 or so. It reminded me a tv station with a/c line noise. For a long time that’s what I thought was going on.
What I did was sit down and hand made a checkerboard in Photoshop of 1 pixel on and 1 pixel off. When I sent it to the laser I could see where rows were getting duplicated.
As long as you make the metric size the machine wants, everything looks great.
Are these lines etched in and outside the image?
I used to have the same problem where it would happen intermittently and problem was solved with a new PC board where the parallel port fed into. It’s been awhile since I’ve looked at it but I think that’s the board I’m referring to. I have a ULS VL 200. They overnighted a new board to me and the problem was solved.