Here’s a few trials I did with laser engraving wooden coasters.
Plywood
MDF
!
Bamboo
!
Settings: 75% power, 100% speed, 2 pass, 1000dpi
I had to manually lighten parts of the image to get enough definition on the bamboo. Which would you choose?
MDF
!
Bamboo
!
4 Likes
Ooh the ply looks good. It would be interesting to see if you could analyse the density minimum, density maximum and the tone response curve of the material. They you can take these values and map them to the image in photoshop to get the best tone response from the material. It would be alot like profiling a printer paper.
Its a completely different method of production, but direct to media (DTM) printing might offer some of the analysis guidelines for getting these characteristics as you can print to virtually any material but you need to be able to work out how many passes are needed to make the final print.
1 Like
2 passes definitely gives more contrast without blowback. But still, apart from the ply, it’s hard to get more than 3 different shades. So I was wondering if there’s a filter in photoshop to reduce the greyscale to just 3 values.
1 Like
I wonder if halftone might give better results when it comes to a range of tones? Sacrifices detail of course.
1 Like
Yes there is and you can vary how you tonally cut it up. change the image mode to grayscale first or it will posterise each individual colour channel.
image-> Adjustments->posterize will do it in basic terms. If you want finer control, us this as an adjustment layer and use something like a curve or levels adjustment layer alongside it to tweak how it is being cut up.
Once you have done this, you can use a gradient map to the map colours across the different values.
What is the upper limit on colours the laser can differentiate in terms of different engraving strengths? If you are able to use 256 different tool settings, you can have a full range of an 8-bit monochrome image file. Map each colour to a different strength which correlates to the pixel value in image file.
(256 separate operations might be a bit much for the laser to handle though!)
2 Likes
I found the most variation is been 100 and 200 RGB value.
I discovered the other day that this is what the laser cutter uses to do different shades at the same power. If you lower the dpi to 300, you can see the different lengths of dash with gaps in between.
ah so you can possibly take 100 as your ‘White Point’/ density minimum and 200 as you ‘Black point’/density maximum and then you have the 100 intermediate values to vary power in order to make 100 tonal values. This is all assuming this is the effect you are going for!
You can artificially limit a file to reduce its bit rate using an output restriction. Easiest is the output values in a levels adjustment. the actual values will all be relative and don’t actually have to sit within the 100-200 range, they just need to have be mapped to the power output of the laser.
1 Like
Next time we’re in the space together I might get you to show me. Photoshop’s functions seem to be endless!