Ppmv

Front 1

Ricco’s Law

Back 1

L•A = Constant at threshold up to 10 minutes of arc. (At fovea) The energy is constant when determining absolute threshold. Does not apply over 10 minutes. This is due to spatial summation.

Front 2

Piper's Law

Back 2

L•A1/2 = C. Between fovea and 10°. This is partial spatial summation.

Front 3

Pieron’s Law

Back 3

L•A1/3 = C. Beyond 10°. Partial Spatial Summation.

Front 4

Block’s Law

Back 4

L•t = C. In temporal (time) summation, the area of illumination is fixed, but the duration varies. Valid for 1millisec to 100 millisec. 10msec at fovea (cones) is best, 100msec at periphery (rods) is best.
*Note: Rods and Cones work the same way for temporal summation. Difference is in the critical limits for each.

Front 5

Composite Theory of Dark Adaptation

Back 5

at the receptor level
1. Stage 1: Outer Segment response.
a. Graded potential of rods (input): linear relationship of light stimulating and first electrical response.
2. Stage 2: Inner Segment Response
a. Log transformation: compressive non-linear transformation.
3. Pooling (temporal and summation) due to convergence
4. Suppression of very slow changes
5. Decision that depends on stage 4, retina decides if there is enough information to send to the optic nerve.
- These satges must be part of any encompassing theory of dark adaptation.

Front 6

Michelson Contrast

Back 6

(Lmax- Lmin)/( Lmin+ Lmax). Values between 0 to 1.

Front 7

Fourier Analysis

Back 7

Analyzing the sine waves of appropriate frequency, contrast, phase and orientation than can construct any spatial stimulus via algebraic addition of the sine waves of different frequency.

This includes the following properties of ganglion cells:
1. Mutually Antagonistic receptive fields.
2. Differing Sizes of Receptive Fields.

Front 8

Spatial Modulation Transfer Function (MTF)

Back 8

Compares the contrast of the object to the contrast of the projected image. (Optic Systems) We process High Frequencies to perceive vision.

Front 9

Human Contrast Sensitivity Function (CSF)

Back 9

Contrast sensitivity is the reciprocal of contrast threshold and is measured in log scales. It forms a Bandpass function and cuts off at the extreme high and low frequencies. Peak 20/20 vision is at 4 cycles/degree.
-At 30 cpd, there are 60 bars each with occupying one minute of arc, therefore the vision is 20/20 (60 mins of arc). If 60 cpd, then 120 bars with one minute of arc. Thus vision is 20/10. If 15 cpd, 30 bars. 20/40 and so on.

Front 10

Weber-Fechner Law

Back 10

ΔL/L = Constant. L is background luminance, ΔL is change in luminance to detect increment. The law only applies when the ratio stays the same. A plot gives curves with different slopes at different intensities.

Front 11

Devries-Rose Law

Back 11

ΔL = L1/2 There are different slopes for different amounts of background luminance.
a. Part 3 – Rods with 0.14 increment (m=1) (Weber’s Law)
b. Part 5 – Cones with 0.015 increment (m=1)

ON TEST AS: Increment threshold varies as the luminance of the background increases. For very low background illuminances, quantal fluctuations in the stimulus account for the slope of the curve relating delta L to log background luminance.

Front 12

Bloch’s Law

Back 12

log ΔL/L. Refers to the duration of the test spot

Front 13

Ferry Porter Law

Back 13

(When increasing the luminance of a flicker, the sensitivity increases for the noticeable flicker in the higher frequencies.) The data reaches a flat constant line of approximately 4 log units. In this instance, the (constant flicker frequency) CCF = a log I. Where “a” is a constant, and “I” is the intensity of the flickering. As illumination is increased, CFF increases linearly. This only applies at the flat linear area; it fails at high and low levels of illumination.

TEST: CFF=k log (luminance) + b

Front 14

Granit Harper Law

Back 14

CFF = k log A. As you increase the area, the CFF threshold increases. This refers to the area of light (while Ferry Porter Law referred to the effects of illumination of light).

Front 15

Broca-Sulzer Effect

Back 15

Effect/Brightness Enhancement: a brief flash seems to be significantly greater than a steady flash with the same luminance.

Front 16

Brucke-Bartley Effect

Back 16

Same as brightness enhancement, except it applies only to flicker and not a steady flash.

Front 17

Talbot-Plateau Law

Back 17

Refers to a flickering light (square wave) that is perceptually steady. Present a flickering light with just above the CFF (perceptually steady) and compare it with a 100 lux steady light. The flickering light will need to be adjusted to 200 lux to match the steady 100 lux light due to the on/off of the flicker. You could also reduce the steady light to 50 lux to match the flickering light.