I am going to use the same image of my grandad as did in the previous test.
I did some researching on laser cutting photographs on glass and for this it was said to inverse the image. Acrylic should be with the same principles, so I prepared my images in inverse. This is very simple to do with photoshop, you can even do it on the laser cutting software. I did it beforehand however so that it would be possible to alter the curves, as this was also advised so that you do not have as extreme variations in shades. The extreme variations in shaded do not show up particularly well as subtle changes in power level are more noticeable and effective.
With the picture in inverse I started to test which line spacing would be best. Think that spacing them closer together should be the best way, but due to the limits of the laser cutter and how the cutting looks on acrylic I do not know if that is the best way, so have prepared it with closer and further apart spacing.
With this test I made sure to have masking tape there in preparation and used 3mm clear acrylic. I tested 30percm, 40 per cm inversed during my booked time on the laser.
When loading images onto apethos they are not imported same size as they are saved. I am unsure as to why, or what logic it follows, it is not to a standard dpi. My image came in 173.81 by 217.2mm so changed to 45% scale, which made it 78.21 by 97.74mm. I made notes so I could figure out what the correct scale was. My image was saved as 55.63mm by 69.51 at 300 dpi. This is 3.1% smaller than the imported image, so I shall have to make all my saved images 3.1% larger than intended.
Now at 78.21mm rather than 55.63 the line spacing is 21.4 per cm not 30, and 28.57 per cm not 40. This is a bit confusing but at least now know what I am working with.
With how much better cutting the images in reverse looked I wondered whether, and so tested, cutting the image not in halftones and just as is, but the negative. Weirdly this ended up looking far less like the original image than the halftone ones, even though it is more detailed. I was really surprised by just how much it distorted the image. One key thing that I found by doing it as the whole image was that it is far less see through in this manner. Being see through I think is something I really like about the other method and gives it a slightly ghostly look which I really like.
With the two halftone tests I find it strange when comparing that the test where the lines are only 20percm the image is far clearer and stands out better. I actually think that this is pretty much the perfect line spacing, with any other changes being negligible.
Until I have the chosen images, I think that the laser cutting is now finished. I intend to use 3mm clear acrylic with 0.1mm on the laser, 20 lines per cm with the images inversed and have masking tape over the back before cutting.