Electronic Appendix to

Computational techniques
enabling the perception of virtual images
exclusive to the retinal afterimage

Staas de Jong & Gerrit van der Veer

Video examples

The following video examples were created for use on a Packard Bell R3450 laptop computer's TFT LCD screen. Please note that other displays may or may not correctly reproduce the colors and greyscale intensities used. Screen resolution is 98 dpi, with maximum brightness. Please adhere to the following when viewing the sequences:

Use a daytime indoors setting, with indirect daylight, and without artificial light.
Use a viewing distance of ± 60 cm.
Support your head by both hands, with your elbows resting on some stable surface.
Focus constantly on the crosshair's center.

Example I: Rasterized display of afterimage intensities
Example II: Trigger ambiguity
Example III: Bias ambiguity
Example IV: Partial ambiguity
Example V: Bias and trigger scrambling
Example VI: Bias scrambling with trigger ambiguity
Example VII: Bias ambiguity with trigger scrambling
Example VIII: Multi-trigger sequence

Experimental sequences & dataset

Below are the two-image sequences that have been used in the experiment. In each case, images will be displayed for 20 seconds when viewed separately. When viewing images in sequence, please apply the same viewing directions as given above for the video examples.

Viewing dry runs: first image - second image - in sequence.
Recognition dry runs: first image - second image - in sequence.
Recognition dry runs, continued: first image - second image - in sequence.
Recognition experimental runs: first image - second image - in sequence.
Recognition experimental runs, continued: first image - second image - in sequence.

The above image pairs were used in a two-samples, randomized controlled experiment, comparing afterimage viewing to normal viewing. The resulting dataset is here.

Software tools

The zipped archive, below, contains the source files of the software used to generate the above image sequences. This software has been written in Max, using the Jitter library for video and matrix processing. The archive has two main directories: bias-trigger/, which contains the source files for generating bias-trigger image sequences; and multi-trigger/, which contains the source files for generating image sequences with multiple trigger images.

In both directories, the main source files are called generate image sequence.maxpat and show image sequence.maxpat. These can be executed, examined and modified directly in the Max programming environment, and have self-explanatory user interfaces. By using the latter with the patterns included in the images/ subdirectories, all image sequences discussed in the text can be reproduced. The underlying rule sets can be adjusted for use with other screen types by referring to the notes on their construction in the text.

This package is licensed as free software; please see the source files for details.

Source files: Afterimage tools

Electronic Appendix to Computational techniques enabling the perception of virtual images exclusive to the retinal afterimage

Video examples

Experimental sequences & dataset

Software tools

Electronic Appendix to

Computational techniques
enabling the perception of virtual images
exclusive to the retinal afterimage