Flash photography changes the picture.



This is a magic trick printing technology that retroreflects incident light to reveal different designs. When a flash is used to take a picture with a smartphone or digital camera, the light is reflected and the hidden design or text is made to emit light and recorded by the camera.

*The same effect can be achieved with headlights

flash print

①About Triggers

The trigger for the flash print to make the hidden design appear is "retroreflective light in the line of sight". The hidden design can be seen by taking a flash photo or by matching the light of the light to the line of sight.

flash print
Flash photography
flash print
Shine headlights on it.
flash print
look through a led magnifying glass

②Technical Overview | Product Specifications

Retroreflection is a method of reflection in which, unlike ordinary reflection, light is reflected directly back toward the light source regardless of the direction from which it strikes.FLASH PRINT uses retroreflective material, a patented printing technology that allows SO-KEN to switch between two different designs through a printing data processing method of its own invention.

Retroreflective *FLASH PRINT fall under this category. Diffuse reflection
The light that hits it is reflected straight back toward the light source, so it appears bright and shiny when viewed from the driver. General light reflection. Light that hits the surface is diffused in different directions due to surface irregularities.
Retroreflective Diffuse reflection

Retroreflective *FLASH PRINT fall under this category Diffuse reflection Specular reflection
Retroreflective Diffuse reflection specular reflection
If there is reflective material on the surface Rough surfaces such as concrete and cloth, etc. Mirrors, metal surfaces, etc.

About an arithmetic data processing method that does not require addition.

This is a special placement printing technology completed only by inkjet that allows two different designs to be seen on one medium: a normal design with non-translucent ink printed on a retroreflective sheet and a design with translucent ink that retroreflects when illuminated by light.

an arithmetic data processing method that does not require addition.

How the hidden design is visible

The hidden design is reproduced by retroreflected "light" such as when taking flash pictures. Since black light does not exist, areas that do not glow are recognized as black.

How retroreflection works

Ink specifications and weather resistance

MIMAKI - Genuine eco-solvent ink CMYKW

Ink weather resistance
Weather resistance
Because of exposure to the outdoors, multiple conditions such as light, rain, wind, and the compatibility between the material and our inks It varies greatly. SS21/ES3/Eco-HS1/HS inks are irradiated with a xenon arc weatherometer at 180W/m² for 1560 hours. In the case of SS21/ES3/Eco-HS1/HS inks, we have confirmed that no significant fading occurs when the inks are irradiated with a xenon arc weatherometer for 1560 hours at 180W/m² and sprayed for 18 minutes during 120 minutes of irradiation.
Flash Print Product Specifications
Ink Oil-based ink for outdoor use.
Paper Outdoor paper.

③Notes on installation and use

Durability period of FLASH PRINT
Approximately 3 years for outdoor use.

Brightness of the environment suitable for gimmicks

It is difficult to see the hidden design in environments with illumination of more than 1600 lux, both indoors and outdoors.

outdoor Illuminance by natural light     in clear weather Approx. 100,000 lux
cloudy weather Approx. 30,000 to 70,000 lux
in case of rain Approx. 10,000 to 30,000 lux
Sunset on a clear day Approx. 100 to 500 lux
Night of the Full Moon 0.2 lux
indoor  Illuminance by artificial light Department Approx. 500 to 1,000 lux
Museum Approx. 50 to 500 lux

Differences in the visibility of hidden designs depending on the brightness of the environment

Results will vary depending on the brightness of the environment even at the same output. The gimmick cannot be reproduced outdoors in daylight or in an environment that is too bright.

Design data retroreflective printing retroreflective printing
Normal visible design Hidden design
Light source for visibility Indoor light or natural light Reflected light during flash photography, etc.
Feature Recognizes "reproduction by color" by the brightness of ambient light. Recognize "light reproduction" of retroreflections.
Visibility Bright space As with colors seen in daylight, visibility increases when the surroundings are bright. As in daylight, light is not visible when the surroundings are bright.
Dark space As with colors seen at night, visibility is reduced when the surroundings are dark. Similar to light seen at night, visibility increases when the surroundings are dark.
When shooting with flash Bright  color Less susceptible to backlighting effects when shooting with flash (Affects visibility of hidden design) Light is bright and highly visible
Dark color Backlighting effect when shooting with flash makes it invisible. Dark light and low visibility
Visibility during flash photography based on a combination of the above data
フラッシュプリント フラッシュプリント フラッシュプリント
In a dark space (approximate example: under a streetlight at night) In a standard space (standard example: in a department store retail store) In brightly lit spaces (standard example: inside a pachinko parlor)
フラッシュプリント フラッシュプリント フラッシュプリント
This is a case where reproduction by light is superior to reproduction by color.   This is a case where reproduction by color is superior to reproduction by light.
Retroreflecting to the angle of incidence

Retroreflecting to the angle of incidence

Retroreflects in the same direction as the angle of incidence of light. It is not visible when the light is not irradiated or from an angle different from that of the irradiated light.

Cautions for the environment

Cautions for the environment

In a typical bright environment, there is always an irradiated light. If your eyes are on the same line as the irradiated light, you will see the hidden reflected light. This is an unavoidable phenomenon due to technical characteristics.

Construction Precautions

The following pages provide detailed information on construction precautions and differences in the way flash photography looks depending on the model of the smartphone.