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Objectives What makes a good material Diffusion patterns versus line screening (gray scaling) What makes a good photo Initial Prep on the Photo – what makes a good photo Contrast Enhancement Sharpening the secret to success CorelDraw vsPhotoGRAVvs 1 Touch Invert Vignette Cutout Lab in PhotoPaint
6 rules of lasering photo Always work in Gray scale (a continuous tone image) or Black and white this depends on the material you are going to laser on Know your materials that you want to work on Make sure that you know your speeds and powers Work only with good photos which shows only the focus no background images Know your adjustment commands Crop to Focus
When we look at materials there arethree characteristics that we need toconsider
1 The first is how well does the material that we are working with hold a small well formed laser dot2 Secondly how well does that material display our image. In other word do we see good contrast. Is there a good difference in colour between the colour of the lasered and non lasered area. For example the best contrast is black and white.3 The third is how good is the material in terms of being consistent. Wood is not good because it has a changing grain, anodized aluminum is very good because it has no grain
Products that hold a dot well are anodizedaluminum, laserable plastic or brass plated steel
Our Number 1 Rule Thus materials that hold a good small dot need to be processed one way while those materials that do not hold a good dot need to be processed a different way Let us look at the two ways we can process an image.
Our two printing methods are:1- Half Toning2 -Error Diffusion
Our Number 2 Rule1- Half Toning – Fine Materials2 -Error Diffusion – CoarseMaterials
Half toning - Definition Halftone is the reprographic technique that simulates continuous tone imagery through the use of dots, varying either in size, in shape or in spacing. "Halftone" can also be used to refer specifically to the image that is produced by this process. Where continuous tone imagery contains an infinite range of colors or grays, the halftone process reduces visual reproductions to a binary image that is printed with only one color of ink. This binary reproduction relies on a basic optical illusion that these tiny halftone dots are blended into smooth tones by the human eye.
Products that typically requirecontinuous tonal image – FineMaterials Anodized Aluminum Black Brass Coated Steel Laserable Plastic Some Marbles Laser It
Half Tones which the laser producesare Better on Anodized Aluminum orBrass Plated Steel
What is Error Diffusion? There is a second set of dithering patterns and these are created using what is called an error diffusion algorithm. These use a technique of diffusing quantization error to neighbouring pixels. Ok let us not get to technical. All you need to understand is that there are a number of error diffusion techniques that are available. Which one that you use is up to you. In CorelDraw we have 3 error diffusion algorithm patterns available to us. These are “Floyd- Steinberg”, “Jarvis” and “Stucki”. Others are “Burkes”, “Scolorq”, “Sierra”, “Atkinson” and “Filter Lite”. Figure 2 and 3 shows some of the more popular patterns that are available to use.
Best Photos Formats to get Tiff or BMP are the best as long as they are not jpeg’s just saved as this format Jpeg is the next best but remember JPEG can comes in a lot of different qualities You may get a PDF but the original file may contain bad quality images
Once we have converted the image to grayscale we will now need to process it to laser engrave it. The Contrast Enhancement Dialogue box allows us to increase the tonal range of the photo that we are working on To do this open up the Contrast Enhancement Dialogue Box
What is Tonal Range When we talk about the tonal range of an image we are referring to the range of tones between the lightest and darkest areas of an image. For example, an image with a wide tonal range will include both dark and light areas (and a range of tones in between). Whereas an image with a narrow tonal range will cover a more restricted range for example it could be predominantly composed of mid-tones. Note: when we look at an image that is a grayscale image we have an image that is comprised of gray pixels that have a value of 0 to 255. Values that are 0 are solid black and values that are 255 are solid white. Pixels with a number in between 0 and 255 are a shade of gray.
Finished Product Engraved Dark Medium Lightestlittle adjustment medium adjustment Big Adjustment
If you are lasering on black brass orblack anodized aluminum you willneed to invert the image so that is is anegative.
We have worked with photos that would traditionally be laser engraved on good material such as laser brass or anodized aluminum. But what about wood, glass and granite? To engrave this material we use what is called the error diffusion technique
To Successfully Laser EngravePorous or Course Material likeWood and Glass we need to doan extra adjustment to ourphotoWe need use an error diffusionpattern
I have increased the tonal range of the photo Original Adjusted
Now the question as to how much I adjust isdependent on what I am putting the image on.If I am going onto metal or plastic I would do alighter adjustment as I can show more detailon this material. If I am going onto wood Iwould use a more drastic adjustment
So the rule of thumb is more detail in yourimage if you are going to go on good materialsuch as laser brass. This is because I amgoing to use the halftone image to print myphoto. Thus I use a smaller adjustment in thecontrast enhancement commandIf I am going on a porous product such aswood I need to get rid of detail. Thus I woulddo larger adjustment in the contrastenhancement command
Remember that the worse (the moreporous) the material that we are workingon the more that we have to removedetail, Thus the better the material theless detail that we need to remove in thephoto
This technique is used all the time inprinting colour photographs becausemore photos are digital and they sufferfrom some sort of fuzziness. TheUnsharp mask will sharpen up thesephotos. I use this technique because itnot only does it sharpens up my imagebut it gets rid of some of the detail that Ican not produce. Thus the more detailthat I can not produce the more I use theUnsharp mask