spot 48

Upper Slider
Change the linewidth

Lower Slider
Change the blurryness of the picture

Colour chooser
Change the colour of the lines by clicking into the textfield.
In the displayed colour range you select the hue in the horizontal direction.
Vertically choose the saturation,
and in the gradient on the right the brightness of the colour.
A click outside the colour chooser closes it.

Switch to the right of the colour field
Invert the colours black and white.

Switch to the right of the invert switch
Switch the shape of the crossings between square and circle.

The Hans-Peter-Grid

A coloured modification of the Hermann-Grid

In a classic Hermann-Grid[5] which consists of a grid with white horizontal and vertical lines on a black background you can observe suddenly appearing gray smudges at the crossings of the white lines. They disappear if you try to fixate them. If a colour is applied to the lines between the crossings, and the crossings themselves left white, coloured smudges can be seen, which are in a complementary grayish colour of the adjacent lines. The effect seems to be dependent on the colour, the thickness and sharpness of the lines. With this blelb-spot you can examine the effect by adjusting these parameters.

Attempts to explain visual phenomena

As Artists and Designers we often discover that visual phenomena can be explained only as a result of superimposed single phenomena.
This is also the case with the Hans-Peter-Grid named after the authors of this article. Even with the classic Hermann-Grid the visual effects are manifold as described in the German articles of Lingelbach and Ehrenstein [2][3].
Some of these effects you can find in other places on this website. See spot01 picture 16 or spot 29. The most popular explanation for the Hermann-Grid-Illusion has been the lateral inhibition of ganglion cells in the retina. But this theory has been proven as inadequate by among others Janos Geier[4] or Peter H. Schiller[5].

Until now we simply can’t explain whats going on in our eyes and brains while looking at the Herman-Grid.
So what’s left to do is ongoing experimenting with pictures and observing precisely.

Recipes

For a classic Hermann-Grid:

Set the shape of the line crossings to a square.
Set the square fields to black.
Set the line colour to white by entering "FFFFFF" into the textfield and pressing the RETURN-Key.
Set the blur slider to 0.

For a Hermann-Grid with scintillation effect:

Set the shape of the line crossings to a circle.
Set the blurryness to a middle value.
Set the line colour to a middle gray by entering "888888" into the textfield and pressing the RETURN-Key.

This even works if you invert black and white with the switch.

Bibliography / Links:

[1] Ludimar Hermann: de.wikipedia.org
[2] Neues vom Hermann-Gitter: Bernd Lingelbach, Walter H. Ehrenstein jr. (2002) auf www.optikum.at
[3] Neues vom Hermann-Gitter und die Folgen: Bernd Lingelbach, Walter H. Ehrenstein jr. (2004) auf www.optikum.at
[4] Stoping the hermann grid illusion by sinus distortion: Geier J, Bernáth L, Hudák M, Séra L, 2008, "Straightness as the main factor of the Hermann grid illusion" Perception 37(5) 651 – 665
[5] The Hermann grid illusion revisited: Peter H Schiller, Christina E Carvey
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge
Perception, 2005, volume 34, pages 1375 - 1397