The dot mode correction in Lightburn is an excellent tool and in early versions of Lightburn Jason realized the problem of a 1 pixel signal producing a sausage shaped 2 pixel burn. This is well explained in the excellent video cited by HeritageNI. In those early days, Jason set the signal output to crop the beam diameter from each end of a pixel string. This worked fine for longer pixel strings but the problen this caused was to eliminate any single pixels in a dither pattern. At the time there were no diode lasers to consider, where the PWM instant switching causes this sausage effect. With a glass tube CO2 laser it is possible to balance the response speed of the HV power supply to speed and power such that you can get round dots for square pixels. Thus in making the single dots disappear we could not get faithful 1pixel = 1 dot replication. As a short term fix, Pass Through was implemented so that no dot processing happened on externally dithered images. Dot shape correction has now been reintroduced and it is a 60% fix for the sausage problem on RF CO2 and fiber lasers where the. beam produces a ROUND dot. However, diode laser do not produce a round dot. As perfectly illustrated by Darren in this video, the dots are typically oval(ish) with a 2:1 aspect ratio. Think logically about that situation and you will see that there is not HALF a pixel burn at the end of each pixel signal but a WHOLE pixel burn. Thus for a diode laser a 1 pixel signal generates a 3 pixel wide burn (long sausages!!!) No amount of dot correction is going to fix this inherent problem. Lightburn is an amazing program that tries to make things simple for new users and has the goal to be a one size fits all program for any laser type. I would say Jason has been about 98% successful so far but there will be perculiaritie for each laser type that cannot be catered for. This video demonstrates one such problem. Darren has set a resolution of 254ppi but he cannot produce pixels shorter than 0.2mm wide That in turn dictates that his horizontal resolution needs to be 25.4mm/0/2mm = 127ppi BUT at the same time his Y DOT height is 0.1mm ie a resolution of 25.4/0.1= 254ppi.. Here is the Lightburn dilema. IF you set the resolution to127 you get a PRESET line interval of 0.2mm but that is not what you want You want a line interval 0.1mm. Effectively you want to scan each line of pixels TWICE to create a 0.2mmx 0.2mm burn. That is THE best resolution Darren can ever achieve for true photo replication. This resolution will be OK for large images 300mm sqaure but will look "blocky" ar 100mm square. Darren has succeded in his goal of of showing that there is more to engraving that fiddling with Lightburn parameters and sliders. The diode burn shape is a physical fact that cannot be changed so what Darren is trying to achieve with his tests and experiments in this video is an acceptable visual compromise. The interesing thing about slate is that it is a BINARY material. Simply put, it is grey compressed sand. When you heat sand it turns to pale grey glass. If you burn the same place twice it does not change colour of the glass. Thus the material can only ever be dark grey and pale grey, just 2 colours (a binary material). The dither test pattern. shows this tolerance to overlapping X axis dots. . The grayscale dithered pattern has been set at 254ppi so only the distance between dots in the X axis is changing between 0 and 255. The changing shades of grey you see in the test pattern is an illusion created by your eye as it mixes the light grey glass dots with the dark grey background. At about 150, the 0.2 wide sausage burns are just about touching. Remeber that the 245 ppi line spacing (Y axis) is already correct for the dot height (0.1mm). So between 150 and 217 the suasage ends are gradually overlapping to exclude all the grey background, Thus beyond a certain point there is no perceived colour change. ("the white lmit"). This is one of those pragmatic compromises that this test appears to indicate and it makes sense to set the max white image level to match this white point. However, there are now futher complications.. The test pattern is a reflection of how different DITHERED shades of grey in an image will appear. There is NO uniforn gradation from black to the "white limit" so an unadjusted image will have all the mid tones "overwhite" and almost uniform. This means the image must be "fiddled with" to remove single and double pixels (say) to restore the correct black/white ratio to the burnt image. Losing pixels means losing detail and this is the juggling act that Darren is trying to perform here. I would say he has done a pretty good job considering all the negative facts he is forced to overcome.

Nice job Darren, I agree #3 is great, great video, thanks for the ground work and info

#3 was the one that caught my eye as well. Lightburn did a pretty good job also. Great video as always.

Great tutorial mate, well done.

Great video by the way, thank you so much!

No3 Way to go my man. Thanks for the info great to hear the Aussie voice.

Great video thank you

its number 4 for me i think ! great video mate thanks

Phew now I dont need to get ImagR as I have Photoshop and didn't want another software to work about. Great video

I like the better contrast on number 5

Have you tried it in ImagR? They have multiple algorithms for slate. Also, I have been sanding my slate smooth first, then I spray paint them flat black which I think gives better detail and grey scale effect (greyer for white than the goldish of slate)

4 or 5 looks the best to me!

I actually like #4

thank for a great video, ive watched both of the slate videos and made my own grayscale test. Now trying to figure out to make a dither test file so if you have tips or files at hand id love the help. Keep up the good word greetings from Germany

Great video and lots of info to take away from it. Is the file you have to get the white output value available to download at all? Trying to get to a point where I'm happy with my image engraving and think this may help.

Hello, do you definitively use photoshop or do you also use imag-r to obtain a photo to engraving?

Thanks for very useful info. Do you use something to finish the coaster surface? Shine or matt spray or wax or…? Trying to find something that would increase the contrast..

I must say, from what can judje from the video, that I may like number 4 better as it seems the dynamic range is wider, with the white being whiter.

I agree #3

I don’t like inverted results on slate? I find I get better depth and definition using un inverted but higher power.

Any Idea on how to get rid of the spots in the slate seen at 10:44 ?

Curious, what power is your diode?

What happens if you use Jarvis? I have typically used Jarvis instead of dither Also does speed make a diffrence to the dot length? I see you varied the power, how about speed? Love your presentation 3 & 5 were my choice too

hi can you explain how or where to set the output white point is?

Hi would you edit the image differently in photoshop if this was a white dog or people please?

I lean to #4 & #5

Are there any free softwares that can do this?

No. 4

for me the nr 5

#4 i think

4