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quantizing artefact


code 1 marcello

Image lifted from Marcel Varallo’s blog

code 1 np

Images lifted from Marcel Varallo’s blog

code 1 smh

Image lifted from the SMH


Image lifted from the Adelaide Advertiser

“…what you find is that the so-called “microwriting”  was simply a quantizing artefact introduced when the original JPEG image had its brightness and contrast adjusted. With the new (slightly higher resolution, and generally much smoother) scan, all that nonsense disappears. There is no ‘microwriting’ there at all: The End.”

Nick Pelling.

Lifted from here:


DS Leane needed a ‘large magnifying glass’ to see the capital letters ‘written in faint pencil on the back of the book.’  GF 105

Then Leane gave the book to someone else – a less busy colleague (say) – and he produced a new rendition of Lean’s faint pencil code.

You have to picture this fellow at work. His desk brightly lit, a negative of the faint pencil code before him, pen in his hand. And he applies the ink, letter by letter.

Producing this:

boxall's code

My question.

Would you expect the quantizing artefact (effect) to be uniform over all the letters?

The assumption being that it was an application of the same ink from the same pen by the same hand on the same surface at the same time and under the same conditions.


Quantizing (gerund) :

form into quanta, in particular restrict the number of possible values of (a quantity) or states of (a system) so that certain variables can assume only certain discrete magnitudes.

“light is quantized into packets of energy”

Artefact (noun) :

something observed in a scientific investigation or experiment that is not naturally present but occurs as a result of the preparative or investigative procedure.

“the curvature of the surface is an artefact of the wide-angle view”




3 Comments Post a comment
  1. Pete: the original photograph is analogue, not digital.

    The digital quantizing artifacts I’m talking about were introduced when the scanned RGB image of the photograph was contrast-enhanced and then JPEG compressed to create the digital image that Gordon is relying on.

    The other two scans of the same photograph were not contrast-enhanced, and so their JPEG images did not have the same quantizing artifacts as the first one.

    January 8, 2019
  2. Nick – looking at the (above) images of the letters R and PANE, could you indicate where the quantizing artefacts can be seen?

    January 9, 2019
  3. relayed from Cipher Mysteries #

    “Quantizing artefacts appear at a very low level (i.e. around clusters of pixels) where some of the high-frequency component (i.e. fine detail) signal gets removed out by the JPEG compression, leaving behind proportionately more of the low-frequency component. When images are enhanced (e.g. contrast-enhanced), a range of frequencies get artificially added to the image as part of the visual ‘boost’: which means that when contrast-enhanced images are compressed, you end up with new low-frequency stuff but not so much high-frequency stuff. These new low-frequency artifacts are basically the quantizing artifacts left behind by JPEG compression.”

    Yep. Got that.

    January 10, 2019

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