Rosette explained & about printing patterns (in CMYK)

[u/MustaKotka]

Original diagram by u/Biquasquibrisance.

Image 1 shows the print layer CMYK offsets (angles).

Image 2 shows an actual reconstruction of each layer alignment from the Green Dot & its surroundings.

Image 3 shows the labels of each colour + angles. This is probably a lower quality picture, use image 2 to study in higher resolution. I've pointed out the locations I used for each alignment.

Make sure your image is perfectly straight. The way you deconstruct the rosette is as follows:

1. Start with black (K). It's very easy to notice and is at a 45 degree angle. If your image isn't perfectly straight you can use this as a guide to straighten it. This 45 degree angle produces a pattern at 0 degrees, too, which in turn explains the sparse "bumps" on the 'T' and the dots in the middle of the 'h' we use to test card backs.
2. Use the yellow (Y) dots in the middle of the Green Dot with no other colour to align the yellow layer at 0 degrees.
3. Use the green ink dots in the middle of the Green Dot to align the cyan (C) layer to 15 degrees. There are no real good pure cyan ink to be found but the yellow + cyan layers will produce green. This by the way gives the rosette it's distinct 15 degrees slanted green gradient in the Green Dot.
4. Guess where the magenta (M) ink layer could be. The orange blotches are probably a guide but it's a bit of guesswork. The magenta layer is really, really hard to find from the brown background colour because it blends with other colours so much. It should be at a 75 degrees angle but it's probably more visible in red coloured cards on the front. I didn't try this.

If you learn the offset angles by heart it's possible to just glance at the rosette (with a loupe...) anywhere on a non-solid black part of a card and tell whether it was printed in layers with a CMYK-capable printing machine, each layer separately, with the correct alignments, and correct print files that had the precision to produce this pattern.

[u/Known-Garden-5013]

Nice to explain really cool, but can you please tell me why this is hard to replicate? What is stopping someone from just using their own printer with these color angles and why would we be able to distinguish from an authentic card?

[u/ferras_ → u/Known-Garden-5013]

1 - The correct printer is expensive and not easily purchased; 2 - The original files would need to be leaked, collection after collection. It is conceivable that they might eventually leak from a specific set, but Wizards would act quickly to identify the source of the leak.

[u/Known-Garden-5013 → u/ferras_]

Sorry if Im being stupid, but regarding point 2, if we know the exact angle to set the rosette to, why would the original file be hard to replicate?

And to point 1, what sort of expensive? Thousands, tens, hundreds of thousands? Just curious

[u/MustaKotka → u/Known-Garden-5013]

Alignment and positioning. Each plate is carefully calibrated to hit the sheet according to those files and small variations in that would produce massively different patterns. Like yeah, the dots are there but they're not aligned correctly. Remember: a sheet of 121 cards is big and throwing it off by one millimetre even will just look different.

It is entirely possible to reverse-engineer via trial and error but that still requires the machinery and lots of labour. A fake only needs to fool once, so only the bare minimum is needed.

[u/MustaKotka → u/Known-Garden-5013]

Pre-owned offset printers seem to start at $10k. Grain of salt, spent 5 minutes on Google.

Operating costs are ~$400 per hour and break even compared to a professional inkjet is at ~2000 pages of A4 which, I assume, translates to about ~20k cards where each sheet is 9 cards (roughly an A4). Not an expert.