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Violation of Bloch's Law that specifies reciprocity of intensity and duration with brief light flashes.

Greene E - Iperception (2013)

Bottom Line: This has been variously described as the Bunsen-Roscoe Law or Bloch's Law, often specified as reciprocity of intensity × duration.The present work tested with flash durations ranging up to 100 ms and also found no reciprocity.This departure from classic principles might be due to the specific range of wavelengths of the light-emitting diodes and to a mesopic level of ambient light, which together would preclude activation of rods.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Neurometric Research, Department of Psychology, University of Southern California, Los Angeles, California, USA; e-mail: egreene@usc.edu.

ABSTRACT
For more than a century researchers have been reporting that the visual impact of a very brief flash is determined by the quantity of photons that the flash delivers. This has been variously described as the Bunsen-Roscoe Law or Bloch's Law, often specified as reciprocity of intensity × duration. Prior research found no evidence for such reciprocity when microsecond-duration flashes from a light-emitting diode array were used to display the major contours of nameable shapes. The present work tested with flash durations ranging up to 100 ms and also found no reciprocity. This departure from classic principles might be due to the specific range of wavelengths of the light-emitting diodes and to a mesopic level of ambient light, which together would preclude activation of rods. The reciprocity of intensity and duration may only be valid with full dark adaptation and very dim flashes that activate rods.

No MeSH data available.


Related in: MedlinePlus

Examples from the shape pattern inventory: The inventory of 360 shape patterns included living creatures, vehicles, furniture, tools, and various other shapes. For most shape patterns, the dots marked only the outside boundary of the shape. Each shape in the inventory was randomly selected for display to a given respondent using an array of red-emitting LEDs. To display a given shape pattern, the LEDs were flashed simultaneously at a specified intensity and duration. For convenience, one can describe this as a singular event, i.e., as “a flash.” Respondents could register that they recognized the shape pattern by saying an acceptable name.
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Figure 1: Examples from the shape pattern inventory: The inventory of 360 shape patterns included living creatures, vehicles, furniture, tools, and various other shapes. For most shape patterns, the dots marked only the outside boundary of the shape. Each shape in the inventory was randomly selected for display to a given respondent using an array of red-emitting LEDs. To display a given shape pattern, the LEDs were flashed simultaneously at a specified intensity and duration. For convenience, one can describe this as a singular event, i.e., as “a flash.” Respondents could register that they recognized the shape pattern by saying an acceptable name.

Mentions: A large variety of shapes can be recognized when displayed as brief simultaneous flashes from LEDs that mark the major contours, especially the outside boundaries (Greene & Ogden, 2012, 2013). Figure 1 provides examples from the inventory of shape patterns that were used in these studies. With flash durations as brief as 3 μs human respondents were able to identify—name—a large majority of the shapes (Greene & Ogden, 2013).


Violation of Bloch's Law that specifies reciprocity of intensity and duration with brief light flashes.

Greene E - Iperception (2013)

Examples from the shape pattern inventory: The inventory of 360 shape patterns included living creatures, vehicles, furniture, tools, and various other shapes. For most shape patterns, the dots marked only the outside boundary of the shape. Each shape in the inventory was randomly selected for display to a given respondent using an array of red-emitting LEDs. To display a given shape pattern, the LEDs were flashed simultaneously at a specified intensity and duration. For convenience, one can describe this as a singular event, i.e., as “a flash.” Respondents could register that they recognized the shape pattern by saying an acceptable name.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4129388&req=5

Figure 1: Examples from the shape pattern inventory: The inventory of 360 shape patterns included living creatures, vehicles, furniture, tools, and various other shapes. For most shape patterns, the dots marked only the outside boundary of the shape. Each shape in the inventory was randomly selected for display to a given respondent using an array of red-emitting LEDs. To display a given shape pattern, the LEDs were flashed simultaneously at a specified intensity and duration. For convenience, one can describe this as a singular event, i.e., as “a flash.” Respondents could register that they recognized the shape pattern by saying an acceptable name.
Mentions: A large variety of shapes can be recognized when displayed as brief simultaneous flashes from LEDs that mark the major contours, especially the outside boundaries (Greene & Ogden, 2012, 2013). Figure 1 provides examples from the inventory of shape patterns that were used in these studies. With flash durations as brief as 3 μs human respondents were able to identify—name—a large majority of the shapes (Greene & Ogden, 2013).

Bottom Line: This has been variously described as the Bunsen-Roscoe Law or Bloch's Law, often specified as reciprocity of intensity × duration.The present work tested with flash durations ranging up to 100 ms and also found no reciprocity.This departure from classic principles might be due to the specific range of wavelengths of the light-emitting diodes and to a mesopic level of ambient light, which together would preclude activation of rods.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Neurometric Research, Department of Psychology, University of Southern California, Los Angeles, California, USA; e-mail: egreene@usc.edu.

ABSTRACT
For more than a century researchers have been reporting that the visual impact of a very brief flash is determined by the quantity of photons that the flash delivers. This has been variously described as the Bunsen-Roscoe Law or Bloch's Law, often specified as reciprocity of intensity × duration. Prior research found no evidence for such reciprocity when microsecond-duration flashes from a light-emitting diode array were used to display the major contours of nameable shapes. The present work tested with flash durations ranging up to 100 ms and also found no reciprocity. This departure from classic principles might be due to the specific range of wavelengths of the light-emitting diodes and to a mesopic level of ambient light, which together would preclude activation of rods. The reciprocity of intensity and duration may only be valid with full dark adaptation and very dim flashes that activate rods.

No MeSH data available.


Related in: MedlinePlus