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Photo preparation for laser engraving.

You could just ask us to get your photos laser ready.

I have talked else where on the blog about "pictures" or "images" and "photos".

For the purposes of everything here at Exeter Laser, a "picture" or "image" is anything with an image type file extension, eg BMP, JPEG, TIFF etc, and it includes graphics, line art, cartoons, corporate logos, etc, but a "photo" is a subset of that, it is a photograph, as in something real that was captured in a camera.

This page deals with PHOTOS, and what YOU need to do to get them ready for laser engraving.

BTW, the images on this page are all links to the full size image, and yes, I know I said image there and not photo.... >;*)

As I have said before, here at Exeter Laser we are in the business of Laser Engraving and Laser Cutting, and we bill in "machine time", what we are not about is a design house or bureau, so while we don't mind tweaking an already suitable photo for laser engraving, we have no interest in getting that photo ready, and you won't want to pay us the machine time hourly rate to do so, hence, writing this guide.

  1. Select a suitable photo - not all photos are suitable, some are just too "busy", or too low quality, or any one of several other failings, all of which will become readily apparent as you progress through this list, and the only real cure is get a more suitable photo... this is the first step, and as such it limits all the following steps. Our sample photo has already had all this cleanup work done, the background knocked out, etc etc.
  2. Decide what size, in mm, the finished laser engraving should be.
  3. At this point I am going to assume that the photo you are working on has already been cropped and edited etc, now look at the image properties, there are two values that we are interested in, they are PRINT SIZE and RESOLUTION.
  4. Print size should be exactly equal to your desired finished laser engraving size, print resolution should be exactly equal to your desired finished laser engraving resolution, resolution should be 127 lines per inch for engraving at 0.2 mm, 254 lines per inch for engraving at 0.1 mm, and 317 lines per inch for engraving at 0.08 mm per line.
    Use RESAMPLE, not resize, to make this change.
    At this point, you are still dealing with a colour photo.
  5. Our sample photo has been set to 254 lines per inch, and has a print size of 2.6 inches square, or 66 mm square, so it will be engraved at 0.1 mm per line.
  6. This step you will possibly want to repeat several times, to get it right, now that the photo resolution and print size matches what the laser will output, you need to reduce the colour depth to 2 bit, eg black and white, eg monochrome, and right away, you will see that unless you select an option (the names will vary dependent upon the software you use) such as error diffusion and dot graphic, the results are going to be somewhat less than pleasing.
    Within the error diffusion and dot graphic itself there are several settings you will want to experiment with, such as contrast, and selection of Floyd / Burkes / Stucki methods of error diffusion, weighted or non weighted, and so on. This is why I said you will probably be repeating this process several times.
  7. The first grey scale image on the right shows this done wrong, on the lower most petal of the flower there is an area of solid black, you need to avoid all areas of solid black or solid white (not counting the background surrounding the photo itself, as we don't want to print engrave that with the laser, which will only print engrave the black dots) the second grey scale image show this adjusted *more* correctly, it still isn't ideal, but it is better than the first attempt.
  8. Again, this is for "positive engraving" eg burning dark areas onto a lighter material, if we are using a dark material like dark marble we need to invert / negative this photo before sending it to the engraver.
  9. If the photo is being engraved onto the reverse side of an object such as a sign or mirror, then it will need to be mirrored, this is not just important for text, which is illegible when done incorrectly, but also for the faces of people we know, mirrored images of everyone else (interestingly, not ourselves, we are more used to seeing ourselves in a mirror, which is why photos of ME always look wrong somehow) also look wrong, in a subtle way.
  10. At this point we need to pay attention to the medium upon which we wish to engrave, if that medium has a structure or pattern or grain or whatever that is of a lower resolution than what we are trying to print at, then the resolution of the material itself is going to be combined with the resolution of the engraving, and the very final image gives a virtual preview of that, by applying a texture to the third image, and selecting a wood grain as that texture.

I'm not saying the final image is exactly what you would get if you tried to take that photo and engrave it on to wood, it isn't, but it certainly is closer to the truth than any of the preceding three images.

In the full size version you can see the pattern is there, but the wood grain simply drowns it out.

At this point you would be going back to step 6 in this process, and trying again and again to improve the final output, and possibly going back to step 1 and simply choosing a better photo, where the definition of better means better for laser engraving on the material of your choice at the size of your choice.

At that point you might even go all the way back to step 1, and not choose a photo at all, but an image instead, for example an artist's line art drawing of this flower would vector engrave on wood at this same scale and look beautiful.

Or you might say OK, it doesn't work on this wood, or wood generally, because the structure of the material is lower resolution than the thing we are trying to print engrave, so we will just go and do it on some glass instead.

I recently, quite literally, spent over three days trying to get a laser engraving of a dead relative right, and of course there was a limited supply of photos, and no way to take any more, and I don't mind admitting I wasted three days on it, before finally giving in, using what to my human eyes looked like the worst photo of the lot, tweaking it as best I could in photo editing software, and then using a completely different material, in my case I went the opposite way, from a fine grained material to a much coarser one, and it worked. The end result was extremely pleasing indeed.

Of course once you have it right for that image and that material, you can duplicate it as often as you like, for that same image and that same material, but change *anything* and you are back to square one and starting from scratch all over again.

This final image in the series is one that will work well, and produce a fairly clear and recognisable flower when engraved on to wood. As you can see, to the naked eye in some ways it looks like the worst of the lot, pale and washed out and haltoned to hell and back, nevertheless, on wood, it will produce an excellent result.

IF all the preceding sounds like Exeter Laser doing their level best to convince you to not ask us to ever do any photo engraving for anyone, ever, then you could not be further from the truth.

Actually taking image 5 in this series and loading it into the laser control software takes mere moments, the software correctly says the finished product will be 66 mm square, and the simulation button simulates the output and says it will take 1 minute and 11 seconds, at that point I can say to the customer are you sure you want me to put this engraving on to this material (though, to be fair, at only 66 x 66 mm it does form a nice test piece to establish baselines for a larger image on the same material) and the customer says yay or nay.

Or just use our photo engraving image processing service, see top of page for link.