Full Version: normal dpi output
From: Peck.Sidara (LAOPADAK) [#16]
11 Apr 2007
To: Mike (MIKEHUNTER) [#14] 13 Apr 2007
Mike,
The DPI setting used in the Epilog driver are square in that the overlap of pixels are in both the x and y-axis. It is something that is discussed in our current manual. There's a greyscale picture of a train engraved at both 300 & 600DPI showing the difference in quality. The difference is in both x and y. I believe it's more dependent on the material and file you're using when engraving whether you can clearly see the different for both x and y vs. just y.
Regards,
Peck Sidara
Epilog Laser
From: Dave Jones (DAVERJ) [#17]
11 Apr 2007
To: Mike (MIKEHUNTER) [#14] 13 Apr 2007
I've done tests on anodized aluminum at a number of resolutions and definitely see the X and Y both increase. For photos I do not send grayscale images directly to the laser when using aluminum. I always use Photograv to convert the photos to pure B&W dots first. Then all text and images are being sent already converted to pure B&W and I get more control over the result.
I've noticed with aluminum that when I set the driver to higher than 300dpi that the dots on the X change depending on the resolution of the image being engraved.
What I mean is that if I engrave a dithered 600dpi image at 600 dpi, or a 1200dpi image at 1200 that individual pixels in the X axis engrave too light, presumably because the firing of the laser is so short and it wasn't enough power to fully affect the anodize.
I find that setting the laser at twice the dpi of the original dithered image solves this since it fires the laser twice in the X axis for each pixel. I find that engraving a 300dpi image with the driver set to 600dpi gives me a good result. Alternately a 300 or 600dpi image engraved with the driver at 1200. But I don't see much change in those over the 300dpi engraved at 600, so that's the one I normally use.
When the image was not a direct division of the driver setting I got less predictable results. For example dithering an image to 400dpi and then engraving at 600 had a sort of beating to it and single pixels don't always engrave correctly on aluminum. Going to 1200 would of course be fine since the 400 is a direct division of 1200.
From: Harvey only (HARVEY-ONLY) [#18]
11 Apr 2007
To: Dave Jones (DAVERJ) [#17] 11 Apr 2007
From: Mike (MIKEHUNTER) [#19]
13 Apr 2007
To: ALL
Mike (MIKEN) - Thanks for the tip, but I don't think that I have a problem. The banding only shows up on aluminium and not any of the other materials that I do. I think that it is because the aluminium just soaks up any out-of-focus beam, so that only the centre of the focus point is engraving (in printing terms, I am seeing dot-loss instead of the more usual dot-gain).
I've not tried engraving a photo onto aluminium, though I would love to - all the ali I do belongs to my customers and it is all text and vector graphics.
One customer demands incredibly small text - 0.9mm (0.035") high - and it was quite a task finding settings which give good results on the fine stuff without blowing away normal sized text and logos.