NATIONAL BUREAU OF STANDARDS REPORT

3789

Photometric Tests of 38 Retroref lective Samples

<NBS>

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT

0201 - 20-2301

NBS REPORT

3789

November 10, lS^

Photometric Tests of 36 Retroref lective Samples

Photometry and Colorimetry Section

Optics and Metrology Division

Project No. TED NBS AE-10002

of the

Airborne Equipment Division

Bureau of Aeronautics

Department of the Navy

Washington 25, D. C.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication, rep Approved for public release by the

unless permission is i

25, D. C, Such pern

cal ly prepared If th

Director of the National Institute of

Standards and Technology (NIST) on October 9, 2015

n part, Is prohibited

ndards, Washington

ort has been speclfi-

>ort for Its own use,

21P- 16/54

Report

on

Photometric Tests

of

36 Retroref lective Samples

Tested for

Airborne Equipment Division

Bureau of Aeronautics

Department of the Navy

Washington 25, D. C.

1. SCOPE

This report gives the results of photometric tests

made on samples of retroref lective devices or materials

produced by several manufacturers. All but two samples

included were colorless; the retroref lected light of

these was colorless.*

These tests were requested by the Visual Landing

Aids Section, Bureau of Aeronautics, Navy Department,

in letter Aer-AE-10 No. 147/11, dated 17 October 1952

as part of Project TED NBS AE-10002.

2. INTRODUCTION

2.1 TYPES OF RETROREFLECTORS

The family of retroref lective devices and materials

can be classified into two basic types: Type I, image

forming, and Type II, trihedral. Either type may be used

as' single units or as mosaic plaques consisting of a number of retroref lectors fabricated as a unit.

2.1.1 Type I Retroref lectors

Type I retroref lectors, the image forming type of

retroref lector, generally consist of a lens and a reflecting surface at the focal surface of the lens. The

lens forms an image of the light source on the focal

* The results of tests of colored retroref lectors will

be given in a subsequent report.
2

surface. The light rays are then reflected from this

point and again pass through the lens, the exit path

being essentially parallel to the entrance path. Because of the aberrations introduced by such a lens, the

focal surface is often not a plane but is shaped to

conform approximately with the locus of the principal

focus.

These retroref lectors may be of either two-piece

construction or one-piece construction. One-piece

retroref lectors are formed by coating the rear surface

of the element with a reflective material which may be

either specular or diffuse. The two-piece type may

have either air or a transparent plastic material between the lens and the focal surface.

The principle of the action of glass beads in paint

is the same as that of the retroref lectors discussed

above except that, unless the index of reflection of the

beads is 2.0, the rear surface of the bead is not precisely at the focus of the lens formed by the front

surface of the bead. The spread of the reflected light

will, therefore, be greater than that of most other

lens-mirror reflectors.

Occasionally image forming type retroref lectors consist of a parabolic or concave spherical reflector with

a reflecting material in its focal surface.

In general, it may be stated that any optical

system which forms a real image of a light upon a reflecting surface will function as a Type I retroref lector

.

2.1.2 Type II Retroref lectors

A Type II retroref lective device generally consists of three mutually perpendicular, plane, specular

reflecting surfaces which form a trihedron. Such a

reflector can be produced by cutting a corner off of a

transparent cube. The reflecting surf" es need not be

silvered since total reflection takes place at the

glass-air interface. Any ray of light which enters the

trihedron at the face opposite the apex angle will be

reflected successively by each of the three reflecting

surfaces. After being reflected by the third plane the

direction of the beam is the reverse of that of the

entrance beam. If it were possible to achieve perfectly
plane surfaces and have these surfaces exactly perpendicular to each other, all incident light beams would

be reflected back exactly parallel to the incident path

but slightly displaced. In practice, some deviation from

parallelism to the incident path is desired and can be

achieved by placing the reflecting surfaces not exactly

perpendicular to each other. If the front surface or the

reflecting surfaces are not perfect planes, the result

will be a spreading of the return beam. Single trihedralretroreflector units are usually made of optical quality

glass which has been ground to the desired precision.

When mosaic plaques of trihedral reflectors are desired,

they are usually made of molded plastic. Because of inaccuracies in molding, the prtcision of small trihedral

reflectors made of molded glass is limited. Some work

has been done in recent years toward making elect roformed

trihedral retroreflectors. This process consists of

electro-deposition of metal upon a precisely ground,

optical-glass master. The resulting metallic shell is

carefully removed from the master in such a way as to

minimize mechanical distortion. The shell is then used

as a retroref lector

2.2 DEFINITIONS OF TERMS USED

Retroref lector - an optical system which receives light

and returns it in a direction closely parallel to

the incident light. (In this report, the terms

retroref lector and reflector are used interchangeably where no confusion will result.)

uCat ' s-eye M reflector - popular name for a single Type I

retroref lector of the lens-reflector type. These

reflectors generally have a specular reflecting

surface in the focal plane.

Corner-cube reflector - a Type II retroref lector (trihedral type).

Embossed lens retroref lector - a plaque of Type I retroreflectors formed by embossing the lens and reflecting surfaces upon a sheet of plastic.

Lens-reflector retroref lector - a Type I retroref lector

consisting of a lens with a reflecting surface at

the principal focus of the lens.
- 4 -

Mosaic plaque - the combination of a number of retroreflectors of either type into a closely spaced,

flat grouping.

T-pihPdrfll retroref lector - a retroref lector consisting

of three mutually- perpendicular plane reflecting

surfaces which form a trihedron.

Triple mirror - popular name for a trihedral retroref lector

.

Reference line - the line between the source light and

the reflector, (see figure l c ) Test distance, D - the distance between the source

light and the retroref lector

.

Incidence angle (synonymous with entrance angle), © - the angle at the reflector formed by the reference line and the normal to the surface of the

reflector. Rotation of the normal counterclockwise from the reference line is considered

positive

.

Observation angle, 0 - the angle at the reflector formed

by the line from the observer to the reflector and

the normal to the reflector. Rotation of the normal

counter-clockwise from the line of sight is considered positive.

Divergence angle - ( Synonymous with angle of deviation),

A - the angle at the reflector formed by the

reference line and the line of sight. Counterclockwise rotation of the line of sight from the

reference line is considered positive. Therefore,

when the source light, the ret roref lector, and the

observer are in the same plane,

A = © - 0

When A and © have the same sign, the line of sight

and the normal to the reflector are on the same

side of the reference line.

Orientation angle, ^ - the angle fixing orientation of

the reflector with respect to its own axis, measured counter-clockwise from a specified orientation.

(Specification of this angle is unnecessary for reflectors having circular symmetry.

)
- 5 -

Azimuth angle, a - the angle, measured counter-clockwise,

between the plane containing the reference line and

the normal to the reflector and the plane containing

the source light, the observer's eye and the center

of the reflector.

Cutoff angle - the angle of incidence at which a unit

ceases to perform as a retroref lector because of its

optical construction.

Effective intensity, I e

- the intensity of a retroref lector

,

considered as a secondary source, which will produce

the same illumination at the position of the observer

as will a point source at the same location as the

reflector.

Normal illumination, E

R

- the illumination produced at the

reflector on a plane normal to the reference line by

the source light.

where I is the intensity of the source light.

Luminance factor, p , - of a non-luminous body, under

specified conditions of illumination and observation

is the ratio of the luminance of the body to its illumination. When the luminance is expressed in footTM

lamberts and illumination in footcandles, the luminance factor of a perfect diffuser is unity.

Specific intensity, Ae , - the ratio of the effective intensity of the source light formed by the retroreflector

to the normal illumination at the ret roref lector

where A is the area of the retroref lector

For a perfect diffuser ( (3 = 1) illuminated and viewed

perpendicularly, A0 = A. Therefore specific intensity

may be thought of as the area of perfect diffuser (in

the plane normal to the reference line) producing the

same intensity as the retroref lector . (In this report

specific intensity is reported as candles per footcandle . )

En = I/D2

( 2 )

(3)

(4)
- 6 -

Specific intensity per unit area, A

p

- is defined as

A

0

= Ae /A = j3cos ©cos 0 ( 5 ) For perpendicular illumination and viewing, A0

is equal tc j3 . Therefore specific intensity

per unit area may be thought of as the product

of luminance factor by an angle factor, where

the angle factor is a measure of the inefficiency

introduced by choice of illuminating and viewing

angles. (in this report specific intensity per

unit area is reported as candles per footcandle

per square inch. )

3. MATERIAL TESTED

The reflectors tested are listed in Table I. The

Stimsonite and the Groteiite “disc 11 reflectors are of

the trihedron mozaic plaque type. The Scotchlite,

Groteiite '‘plate 11

, and the Prismo reflectors are made

with beads. The . Reflexite reflectors are of the embossed lens type. The Cataphote and Persons-Majestic

reflectors are individual units of the “cat ' s-eye“

type.

The samples designated with an asterisk were supplied by the Coast Guard. The remainder of the samples

had been previously sent to the National Bureau of Standards by the manufacturers.

4. TEST PROCEDURE

All samples were tested on the 750-foot photometric

range at the Bureau by visually matching the apparent

intensity of the reflector with that of a calibrated comparison lamp. Figure 1 is a schematic representation of

the arrangement for tests on this range.

The observation stations and source light are located in a horizontal plane along the parapet of a

building. The reflector was mounted on a goniometer and

rotated about a vertical axis. Therefore, the azimuth

angle was zero for all observations.

Stimsonite reflectors were mounted with the central

dividing line vertical and with the point designated “TOP 11 up (except as noted). The Groteiite disc was mounted

with the manufacturer's name up and with t>e vertical

diameter of the disc passing through the n0' 1 in the type

number. These positions are taken as the base positions
- 7

-

(orientation angle zero). All other reflectors tested

had approximate circular symmetry and hence the results

obtained were substantially independent of the orientation angle.

The source light used is generally a Type 4561

PAR-46, flashing-signal lamp, rated at 5*3 amperes, 26

volts. The intercity of this lamp is controlled manually

at the reflector eid of the range by adjusting the output voltage of a variable autotransf ormer . The ammeter

is in the circuit for monitoring purposes.

The illumination at the retroref lector is measured

with the photocell which is mounted close to the reflector

under test. This photocell is part of an ilium 'nometer

which has been designed with a zero-resistance circuit.

Figure 2 is a circuit diagram of the illuminometer.

The action of this circuit is as follows. Resistor R2

is adjusted so that no current passes through galvanometer M2 . Under these conditions,

IP = I1R3/R2 (6)

(with sensitivity switch S3 closed so resistance Rq is

shorted out). Since no current is flowing through the

galvanometer, the photoelectric current Ip is equal to

Ip, and the photocell is looking into a circuit whose

effective resistance is zero. Then

!p = I]R

3

/R

2 (7)

Ip is maintained constant by means of resistors R3

and Rr? and milliammeter M-] . Therefore, if Rp is known,

Ip is 'determined. But

Ip = kE ( 8 ) where E is the illumination on the cell, so

E = IpRykRp ( 9 ) The photoelectric cell is sufficiently well shielded

that it is significantly affected only by the illumination

from the source light. Hence

so that

En

= K/R2 ( 10 )
3

The sensitivity switch S-, is opened to increase the voltage

applied to the photocell-^loop when the illumination on the

cell and 1^ are high. This requires an increase in the

resistance^of R2 and hence the accuracy and ease of adjustment are increased.

Since the response of the photoelectric cell is not

exactly linear with illumination over the range of illumination used, K of equation 10 is not exactly constant.

Therefore, the illuminometer was calibrated at values of

illumination throughout the range used.

Generally a fixed level of illumination was maintained

at the reflector. Variations of atmospheric transmission

were offset by varying the intensity of the source light as

necessary. In a few cases, this source light did not give

sufficiently high levels of illumination. In these cases

a projector (permanently located at the source light position and operating at a fixed intensity) was substituted

and the changes in the illumination on the reflector

observed.

Single retroref lector units manufactured by Stimsonite

and Grotelite and single panels of Reflexite were used as

test specimens. Because of the small cross-sectional area,

and hence the low specific intensity, of the Catophote and

Persons-Ma je st ic Button units several of these units were

assembled into a group and used as a test specimen. The

results were averaged for the number of units used.

Samples 4 inches by 4 inches were cut from larger samples

of Scotchlite for use as test specimens. A five-inch disc

furnished with Prismo Reflective Paint by the Naval Air Test

Center was used as a test specimen of this material.

With the retroref lector mounted on the goniometer and

oriented at the desired angle of incidence, the source light

intensity is adjusted for the necessary illumination at the

reflector. Then the intensity of the comparison lamp,

separated horizontally from the retroref lector by approximately 0.5°, is varied by adjusting the current of this

lamp so that the intensity of the comparison lamp appears

equal to that of the reflector. The average current for

several matches is obtained. The intensity of the comparison

lamp, and hence the effective intensity I e of the retroreflector, corresponding to the average current, is obtained

from the intensity-current calibration curve of the lamp.
i - 9

-

Matches are made for each desired angle of incidence and

angle of divergence. (For 0° angle of divergence the

observer's eye was placed as close to the source light

as physically possible. Results thus obtained are slightly

different from those which would be obtained if it were

possible for the observer's eye to be at the center of the

source light.) The cutoff angles were determined by visual

inspection on a 100-foot range using about 50 times the

illumination used for the specific intensity measurements

on the 750-foot range. This was done because the specific

intensity of some reflectors at the larger angles of incidence when tested on the 75'0-foot range was below th^

observer's threshold even though the optical cutoff

' not been reached.

The specific intensity, the specific intensity per

unit area, and the directional reflectance can then be

computed by means of equations 3, 4, and 5 for each angle

of incidence and divergence used.

4.1 EFFECTS OF ATMOSPHERIC TRANSMISSION

|

Note that the atmospheric transmission does not appear

as a factor in equations 3 and 4 since the illumination at

the reflector is measured there, and not computed from the

intensity of the source, and since the reflector and the

comparison lamp are viewed through essentially the same

path. Hence, even though a test distance of 750 feet is

used, measurements can be made in hazy as well as very

clear weather. However, it has been round that generally

when the transmittance over 75 0 feet is less than about

0.85, the moment -to-moment changes in transmission and the

light scattered back from the source light beam interfere

with the measurements.

4.2 CHOICE OF ANGLES USED

The test request asked for measurements for incidence

angles varying from normal incidence to the incidence angle

at which the specific intensity falls to one-tenth that at

normal incidence and for divergence angles of 0°, 0.5°, and

1°. Because of the interest in the application of these reflectors to purposes other than that for which the tests

were originally requested, the tests of some of the reflectors have been expanded to include other angles of incidence and divergence.
10

4.3 CHOICE OF TEST DISTANCE

The effects of changes in test or observation distance

on specific intensity measurements are not known quantitatively. Observations made prior to this test indicate that

the test distance as well as the angular size of the source

and the receiver can have a significant effect upon the

results obtained. In general, if the test distance is too

short, the specific intensity increases as the test distance

is increased. When the test distance is above a minimum

value, the specific intensity is constant and independent

of test distance.

The magnitude of this effect and the minimum test

distance vary with the type of reflector used. Results

obtained by Finch (Highway Research Bulletin No. 34)

indicate that this minimum distance for mosaic plaques of

trihedral retroreflectors::1 is greater than 200 feet.

In view of the uncertainties of the effect of test

distance, it appears desirable to use a test distance

which is approximately the distance at which the reflector

will be viewed in service. Hence, if the long-range performance of the retroref lectors is of primary importance,

the test distance should be as great as possible. A test

distance of 750 feet was chosen for this work since it is

convenient and is believed to be sufficiently great that

increasing this distance will not change the specific intensity of the reflectors tested significantly.

At this distance the angular size of the source light

was approximately 2.7 minutes.

The angular size of the largest reflector tested was

about 2.5 minutes. To an observer adapted to the luminance of the background, approximately 0.02 footlambert,

reflectors of this size are sufficiently close to point

sources that the effects of their size and shape upon the

intensity match are insignificant.

5 . TEST RESULTS

The results of these tests are given in Tables II to

VIII. In each table are given the results of the tests

of the retroref lectors of one manufacturer. When available and applicable, data for more than one sample of a

given type of reflector have been included to give some
11 -

measure of the range of reflectance for different samples

of the same product. Values of specific intensity are given

for the retroref lectors of unit (fixed-area) construction.

Values of specific intensity per unit area and luminance

factor are given for all samples. Approximate values of

the angle of cutoff are included in these tables.

In these tables, the entry of a dash instead of a

numerical entry indicates that the specific intensity of

the sample, under these conditions of illumination and

view, was too low to permit measurement. No entry indicates that no observation was made at this point.

Figure 3 consists of broken-line graphs of several

representative samples of different manufacturers showing

the variation in specific intensity per unit area with

change of incidence at 0° divergence. Figure 4 consists

of broken-line graphs for the same samples showing the

variation in specific intensity per unit area with change

in angle of divergence at 0° incidence. Performance of

all the types of retroref lectors tested is shown in a

similar manner in sets of two figures for each manufacturer's material. These figures are:

Stimsonite - figures 5 and 6;

Scotchlite - figures 7 and 8 ; Reflexite - figures 9 and 10

Cataphote - figures 11 and 12;

Persons-Majestic - figures 13 and 14;

Grotelite - figures 1§ and 16;

Prismo - figures 17 and 18

6. DISCUSSION

6.1 APPLICATION OF MEASUREMENTS

The observational data obtained have been presented

as specific intensity, as specific intensity per unit area,

and as luminance factor. In general the use of specific

intensity is advantageous when studying the performance

of retroref lectors of unit construction (with a fixed area).

The use of specific intensity per unit area is advantageous

in studying the performance of retroref lective slvet material

where the area is not fixed and in comparing the ll eff iciency' 1 of reflectors of different areas. The luminance factor may

be used advantageously in comparing the performance of retroreflective materials with that of paint.
6.2 COMPUTATION OF VISUAL RANGE

The visual range of a retroref lector may be found

from the relation

B 0

= AeEn

T V/V2 or (11)

S 0

= A

e IT 2V/V

1+ (12)

where E 0 is the threshold illuminance of the observer,

En is the normal illumination at the reflector, kQ is

the specific intensity for the applicable angles of

incidence and divergence, I is the intensity of the

source illuminating the retroref lector, T is the atmospheric transmittance and V is the visual range of the

reflector.
- 13

I

REFERENCES

1. Kinpslake, R., Jour, of Opt. Soc. of Amer. 28, 323 (1933)

2. Steel, W. H., Australian Jour, of Sci. Research, Sec. A, 2,

335 (19^9)

3. Van Lear, G. A., Jr., Jour, of Opt. Soc. of Amer. 3P,

462 ( 1940 )

4. Goldberg, G., Jour, of Opt. Soc, of Amer. ^8, 409 (1948)

5* 1953 SAE Handbook, Soc. of Automotive Engineers, p. 813

(1953)

6. Finch, D. M., Highway Research Board Bulletin No. 34,

p. 21 (195D

7. Pocock, B. W. , and Rhodes, C. C. , Highway Research

Board Bulletin No. 34, p. 40 (195D

8. Rhodes, C. C., and Pocock, B. W. , Testing and Research

Division Report No. 167 . Michigan State Highway

Department (1951)

9. Little, W. F., and Parker, A. E., Illuminating Engineering 789 (1942)

i)

Table I List of Reflectors Tested

Material Tested

STIMSONITE No. 19

STIMSONITE No.- 12

STIMSONITE No. 10

Manufacturer Identification Marks

Stimsonite Plant, AGA CG#2*

Div., Elastic Stop Nut 1949-3

Corp. of America, NATC-1

Chicago, Illinois.

CG#1*

1948-1

1948-2

CG#3*

CG#4*

1948-2

SCOTCHLITE, Standard Scotchlite Reflective CG-CA-1*

Signal Silver #244 Products Div., Minnesota

Mining & Manufacturing

SCOTCHLITE, Standard, Co., St. Paul, Minnesota CG-CI-1*

"C“ Black #226

SCOTCHLITE, Wide

Silver #230

Angle, CG-CI-3*

SCOTCHLITE, Wide

“C“ Black #234

Angle

,

CG-C-2

SCOTCHLITE, Wide

UCU White #246

Angle, CG-246*

SCOTCHLITE, Wide

**C“ White

AngleNATC-2

SCOTCHLITE, Flat

Silver #2250

Top, CG-0N-2A*

SCOTCHLITE, Flat

Silver #2250

Top, CG-ON-2*

SCOTCHLITE, Wide Angle,

Flat Top, Silver #2270

CG-0G-4A*

CG-OG-4*
2

Material Tested Manufacturer Identification Marks

SCOTCHLITE, Wide Angle,

Flat Top, White

NATC-3

SCOTCHLITE, Wide Angle,

Flat Top

CG-EA*

SCOTCHLITE, Flat Top,

Silver #2200

1949-1

SCOTCHLITE, Standard,

Signal Silver #244

1949-3

SCOTCHLITE, "Vinylite

Base 11 Silver

1949-2

REFLEXITE, C69R Clear Reflexite Corporation,

New Canaan, Conn.

CG-Clear

REFLEXITE, C 69R CG-C69R

REFLEXITE, C 56R CG-C56R

REFLEXITE, Co9Met CG-C69Met

REFLEXITE, C^6 Met CG-C56 Met

REFLEXITE, C-WA-0. 070' 1 1949-C=WA

CATAPHOTE, #1A Crystal Cataphote Corporation

Toledo, Ohio

#1A Crystal*

CATAPHOTE, #3 Crystal ii 3 Crystal*

PERSON S-MAJEST IC, Clear Persons-Majestic Mfg. Co.

Worcester, Mass.

PersonsMajestic*

« i
Material Tested Manufacturer Identification Marks

GROTELITE, Type 105 Grote Mfg. Co., Inc.

Bellevue, Kentucky

Grote

GROTELITE, “Plate,” Grote

Silver

• ?

Disk*

Plate*

PRISMO Ref lectorized

Paint

Prismo Safety Corp

Huntingdon, Penna.

NATC-4

Table II

Retroref lector s Manufactured by Stimsonite

Plant, AGA Division of Elastic Stop Nut Corporation of America

a. Specific Intensity

Angle

of Incidence 0

° 1/4° 1/2° 1

° 2

°

Style #19 - Clear (4 3/4" diameter) -

0

° 330 220 68 6.1 0.80

- 20 ° 210 110 31 2.8 0.46

-30° 95 64 20 2.3 0.48

-40° 36 28 15 2.2 0.54

+20 ° 190 110 47 3.6 0.60

+ 10 ° 34 bd 24 2.5 0.54

+40° 35 24 13 3.3 0.57

Angle of Divergence 31 Ipr o'

Cutoff Angle - Approximately 60°

Style 19 - Clear (4 3/4" diameter) - (CG#2)

(Dividing line Horizontal)

0

° 330 290 60 6.1 1.6

- 10 ° 300 230 ^3 4.6 1.1

- 20 ° 170 l4o 33 4.1 O .76

-30° 28 22 7.5 0.84 0.28

-40° 5.8 3.9 2.1 0.3b --

Cutoff Angle - Approximately 60°

Style if 19 - Clear (4 3/4" diameter) -(NATO

0

° 330 210 35 6 . 6

- 10 ° 330 170 40 4.4

- 20 ° l60 86 21 2.3

-40° 27 21 8.0 3.3

-6o° 3.4 3A 2.8 2.9

Cutoff Angle - Approximately 60°

2

I

1

' Table II (Continued)

a. Specific Intensity (Continued)

Angle of

Incidence

Angle of Divergence

0° 4 o" i

1 1/2° 1° 2° 3° 40 5° . . 6°

Style #19 - Clear (4 3/4w diameter) (1949-3)

0° 270 150 56 6.1 1.0 0.50 0.35 0.29 0.24

-10° 180 110 39 3.9 0.68 0.46 0.32 0.26 0.23

-20° 120 6l 26 2.6 0.50 0.30 0.23 0.21 0.18

-30° 49 31 11 3.2 0.58 0.36 0.25 0.18 0.17

-4o° 14 10 7.1 2.8 0.87 0.42 0.28 0.18 0.16

-5o° 1.2 1.0 0.94 1.0 0.61 0.35 0.29 0.22 0.16

Cutoff Angle - Approximately 60 O

Style #12 - Clear (2 3/4“ diameter) -- (CG#1)

0° 39 38 3.8 0.60 0.38 0.28 0.20

-10° 33 28 3-8 0.50 0.28 0.24 - -20° 15 10 3.3 0.43 0.22 - - -30° 6.2 5.8 2.2 0.36 0.20 - - -40° 2.9 2.4 0.82 0.32 - - -

+10° 32 23 4.0 0.50 0.32 0.25

+20° 15 11 2.5 0.50 0.28 - - +30° 6.4 5.1 1.7 0.50 - - - +4o° 3.3 2.5 1.2 0.30 - - - Cutoff Angle - Approximately 60°

Style #12 - Clear (2 3/4 w diameter) (1948-1)

0° 26 26 22 5.2 0.58

10° 21 19 16 3.6 0.61

20° 12 12 9.6 1.4 0.42

30° 5.0 5.2 3.7 1.02 0.44

40° 2.5 2.3 1.5 0.89 O .36

50° 0.81 0.71 0.50 0.42 0.27

Cutoff Angle - Approximately 60°

Style #12 - Clear (2 3/4** diameter) (1948-2)

0° 68 59 40 3.4 0.54

10° 54 38 19 0.77

20° 27 16 6 .

30° 15 7.9 3.3

40° 2.2 1.7 1.1

50° 0.60 0.50 0.34

Cutoff Angle -- Approximately 60°
• . * , • . '

.• t • . t # .
-3-

Table II (Continued)

a. Specific Intensity (Continued)

Angle

of In- Angle of Divergence

cidence 0° 1/4° 1/2° 1° 2°

Style ft 10 - Clear (Red Back) (1 1/2'1 diameter) -

0° 4.0 4.8 4.0 1.2 0.14

-10° 3.9 3.9 3.6 0.87 0.15

-20° 1.5 1.6 1.2 0.44 0.10

-30° 0.95 0.87 0.65 0.37 ~ -4o° 0.54 0.40 0.34 0.20 -

+1C° 4.2 3.7 3.9 1.3 0.15

+20° 1.5 2.2 1.9 0.65 0.13

+30° 0.75 0.65 1.0 0.35 0.11

+4o° 0.34 0.35 0.35 0.15 -

T|0

(CG#3)

Cutoff Angle - Approximately 60°

Style ftlO - Clear (White Back) (1 1/2" diameter - (CG#4)

Jo 0

°

0° 14 10 5.6 0.35 0.12

-10° 13 11 4.5 0.38 0.096

-20° 5.3 3 .7 2.6 0.30 0.11

-30° 2.2 2 .0 1.2 0.26 0.076

-40° 0.77’ 0 .77 0.58 0.24 0.049

+10° 12 10 5.0 0.42 0.097

+20° 5.1 5 .6 2.7 0.32 0.062

+30° 2.8 2 .7 1.7 0.24 0.097

+40° 1.2 0 .88 0.78 0.13 0.087

Cutoff Angle - Approximately 60°

Style yf 10 - Clear (1 1/2" diameter) (1948.

0° 19 15 8.7 2.3 0.39

10° 14 12 6.6 1.4 0.38

20° 6.2 4.1 3.1 O .63 0.32

30° 4.2 2.5 1-9 0.48 - 40° 2.6 1.5 0.77 0.29 - 50° 0.66 0.50 O .36 0.10 -

Cutoff Angle - Approximately 60 c

J
- •

'

'

.

•

.

'

il
Table II (Continued)

b. Specific Intensity per Square Inch

Angn e n 1 of' i! n1 - Angle of Divergence

ciuence 0° ~T7T\° 1/2° 1° 2° 3° 4° 50 6 c

Style #19 - Clear - (CG #2)

0

° 19 12 3.9 0.35 0.046

-20° 12 6.6 1.3 0.16 0.026

-30° 5.5 3.7 1.2 0.16 0.023

-4o° 2.1 1.6 0.39 0.13 0.031

+20° 11 6.2 2.7 0.21 0.035

+30° 4.9 3.9 1.4 0. 14 0.031

+40° 2.0 1.4 0.75 0.19 0.033

Cutoff Angle - Approximately 60°

Style #19 - Clear -(CG#2)

(Dividing line horizontal)

0° 19 17 3.4 0.35 0.099

-10° 17 14 2.9 0.27 0.063

-20° 1 n 3.0 2.2 0.24 0.044

-30° 1.6 1.2 0.43 0 . 049 0.016

-40° 0. 34 0.23 0.12 0.021 -

Cutoff Angle - Approximately 60°

Style #19 - Clear (NATC-1)

0° 22 12 2.1 0. 38

-10° 19 9.7 2.3 0.2b

-20° 9.3 9.0 1.2 0.16

-40° 1.9 1.2 0.47 0.19

-b0° 0.20 0.20 0.1b 0.17

Cutoff Angle '- Approximately 60°

Style #19 - Clear (1949 - 3)

0° 16 8.9 3.3 O.36 0.099 0.030 0.020 0.017 0.014

-10° 10 6 .4 2.3 O.23 0.040 0.027 0.019 0.013 0.014

-20° 7.1 3.6 1.6 0.16 0.030 0.018 0.014 0.012 0.011

uo° 2.9 1.8 0.66 0.18 0.034 0.021 0.013 0.011 0.010

-40° 0.84 0.99 0.42 0.16 O.031 0.029 0.016 0.011 0.0092

-9o°

0 ut of f

0.074

Angle - 0. Obi 0.099 0.099

Approximately 60°

0.036 0.020 0.C17 0.013 0.0092

Table II (Continued)

b. Specific Intensity per Square Inch (Continued)

Angle

of In- Angle of Divergence

_ 4 j — no l /iia I /oo to no cidence 0° 1/4° 1/2

° 1

° 2 ° 3° 4° —50

CD i

—

>>

CO #12 - Clear - (CG #l)

0

° 6.2 6 . 2 0.62 0.10 0.062 0.046 0.034

-10° 5.4 4.7 0.62 0.083 0.046 0.039 - -20° 2.4 1.7 0.54 0.071 0.036 - - -30° 1.0 0.96 0.37 0.059 0.034 - — -4o° 0.47 0.39 0.14 0.053 - - -

-*-10° 5.3 3.8 0.66 0.083 0.053 0.041 e. 4

- 20 ° 2.4 1.8 0.41 O.O 83 0.046 - - +30° 1.0 0 . 84 0.27 O.O83 - - - +40° 0.54 0.41 0.19 0.049 - - Cutoff Angle - Approximately 60°

Style #12 - Clear (1948-1)

0

° 4.2 4.2 3.5 0.84 0.094

10 ° 3.4 3.0 2.6 0.60 0.098

20 ° 1.9 1.9 1.6 * 0.23 ,0.068

30° 0.81 0.84 0.59 0.15 0.071

40° 0.4l 0.37 0.25 0. 14 0.058

50 0.13 0.12 0.081 0.068 0.044

Cutoff Angle - Approximately 60°

Style #12 - Clear (1948 - 2)

0

° 11 9.5 6.5 0.55 0.088

10° 8.8 6 . 2 3.2 0.12

20° 4.4 2.7 1.1

30° 2.4 1.3 0.53

40° 0.36 0.28 0.17

90° 0.097 0.081 0.056

C ut off Angle - Approximately 60°

Style #10 - Clear (Red Back)(CG #3)

0° 2.4 2.8 2.4 0.71 0.085

-10° 2.3 2.3 2.1 0.51 0.090

-20° 0.89 0.97 0.68 0.26 0.059

-30° 0.56 0.51 0.39 0.22 - -40° 0.32 O .23 0.20 0.12 - (Continued on next page)

Table II (Continued)

b. Specific Intensity per Square Inch (Continued)

Angle

of In- Angle of Divergence

cidence 0

° 174*° 1 /2 ° l° . 2 ° 3

Style 10 - Clear (H a d Back) vCG ft 3

' i(C ont inued)

+ 10 ° 2.5 2.2 2.3 0.78 0.090

+20 ° 0.89 1.3 1.1 0.39 0.076

+30° 0.44 0.39 0 . o2 0.22 O.O63

+4o° 0.20 0.22 0.22 0.090 -

C ut of f Angle - Approximately 60°

Style 10 - Clear (White Back) (CG #4 )

0

° 8.3 6.1 3.3 0.21 0.073

- 10° 7.3 6.4 2.6 0.22 0.057

-20° 3.1 2.2 1.6 0.18 O.O67

-30° 1.3 1.2 0.72 0.16 0.045

-40° 0.46 0.46 0.34 0. 14 0.029

+10° 6 .

6 .

3.0 0.25 0.057

+20° 3.0 3.3 1.6 0.19 0.036

+30° 1.6 1.6 1.0 0.14 0.057

+40° 0.72 0.52 0.46 0.075 0.051

C ut of f Angle - Approximately 60°

Style #10 - Clear (1948-2)

0° 11 8.7 . 5.0 1.4 0.23

10° 8.1 6.7 3.8 0.82 0.22

20° 3.6 2.4 1.8 0.37 0.18

30° 2.5 1.5 l.l 0.28 - 40° 1.5 0.86 0.45 0.17 - 50° 0.38 0.29 0.21 0.061 - Cutoff Angle - Approximately 60°

Table II (Continued)

c. Luminance Factor

Angle

of In- Angle of Divergence

cidence 0

P 1/4° 1° 2° y> 4° 5° b°

Style#19 -Clear -(CG #2)

0° 8600 5700 1800 100 21

-20° O300 3400 940 82 14

-30° 3300 2J00 710 98 17

-4o° 1000 1200 700 99 25

+20° 5600 3200 1400 110 18

+30° 2900 2400 830 87 19

+40° 1000 1100 580 150 25

Cutoff Angle - Approximately 60°

Style #19 - Clear - (CG#2)

(Dividing line horizontal)

0° 8000 7600 1600 loO 43

-10° 8100 6400 1200 120 30

-20° 5200 4200 1100 120 23

-30° 1000 760 200 30 10

-40° 200 180 94 16 - Cutoff Angle - Approximately 00 p Style #19 - <Hear - (NATC-1)

0° 10000 5500 930 130

-10° 9100 4600 1100 120

-20° 4800 2000 620 82''

-40 1200 930 360 150

-60° 300 370 290 310

Cutoff Angle - Approximately 60°

Style #19 - Clear (1949-3)

0° 7 200 4000 1500 100 27 14 9.3 7.8 6.5

-10° 4800 3000 1100 110 19 13 8.9 7.2 6.5

-20° 3700 1800 800 80 15 9.3 7.2 6 .

5-7

-30° 1800 1100 400 110 21 13 9.5 6 .

0 .

-4o° 650 460 320 130 4l 20 13 9.0 7.8

-50° Si 67 02 06 42 24 21 16 12

Cutoff Angle - Approximately 60°

Table II (Continued)

c. Luminance Factor (Continued)

Angle of

Incidence

Angle of Divergence

QO ~l/4° 1/2° 1° 2° 3° 4°

Style #12 - Clear-( CG #D

0° 2800 2800 280 45 28 21 1 5

-10° 2500 2200 290 39 22 18

-20° 1200 880 280 37 19 - — -30° 620 590 220 37 21 - - -40° 370 310 110 42 - - - +10° 2500 1800 310 39 24 19 - +20° 1300 910 210 42 14 - - +30° 640 510 160 49 - — - +40° 420 320 140 37 - - -

Cutoff Angle - Approximately 60°

Style #12 - Clear (1945! - 1)

0° 1900 1900 1600 380 43

10° 1600 1400 1200 280 46

20° 1000 960 800 180 34

30° 490 510 360 99 42

40° 320 290 190 110 44

50° 140 130 88 73 47

Cutoff Angle - Approximately 60°

Style #12 - Clear (1948-2)

0° 5100 4300 2900 250 40

10° 4000 2900 1500 98

20° 2200 1400 560

30° 1500 770 320

40° 280 210 130

50° 110 89 61

b*

Cutoff Angle - Approximately 60°

- 9

-

Table II (Continued)

c. Luminance Factor (Continued)

Angle of Angle of Divergence

Incidence 0° 174 ° 1/2® 1° 2° 3

0 4-° 5° 6°

Style #10 - Clear“ (Red Back) -(CG #3)

0° 1100 1300 1100 320 39

-10° 1100 1100 1000 240 42

-20° 46 0 700 350 130 31

-30° 340 310 240 130 - -4o° 230 180 IbO 94 -

+10° 1200 1000 1100 360 42

+20° 46o 660 780 200 38

+30° 270 230 370 120 37

+4-0° 170 IbO IbO 69

Cutoff Angle - Approximately 60°

Style #10 - Clear (Whitei Back) (CG #4)

0° 3300 2800 1700 930 33

-10° 3b00 3000 1200 110 27

-20° IbOO 1100 800 92 37

-30° 780 740 44o 76 23

-4o° 370 370 270 110 23

+10° 3200 2800 1400 120 27

+20° IbOO 1700 820 97 18

+30° 1000 970 bOO 86 34

+4o° 76 0 400 360 77 39

Cutoff Angle - Approximately 60°

Style #10 - Clear (1948-2)

0° 7100 3900 2300 610 100

I0C 3800 3100 1800 380 100

20° 1900 1200 940 190 94

30° 1500 900 680 170 - 4o° 1200 660 340 130 - 7o° 420 320 230 67 - Cutoff Angle - Approximately 60°

1

Table III

Retroref lectors Manufactured by

bcotchlite Keilective Products Division

of Minnesota Mining and Manufacturing Co.

a. Specific Intensity per Square Inch

Angle of Angle of Divergence

Incidence 0° h- -p ci./ z ° 1° 2°

Standard, Signal Silver #244 (CG - CA-1)

0° 2.1 0.68 0.52 0.33 0.12

-10° 1.6 0.77 0.56 0.33 0.10

-20° 0.21 O.lb 0.13 0.10 0.077

-30° 0.036 0.019 0.015 0.013 0.0092

-4o° 0.020 0.010 0.0037 0.00/6 0.0064

Cutoff Angle - Approximately 60°

Standard, '*C W Black #226 (CG-CI-1)

0° 1.6 0.82 0.68 0.50 0.22

-10° O.96 0.48 0.39 0.23 0.11

-20° O.lb 0.070 0.056 0.033 0.015

Cutoff Angle - Approximately 30°

Wide Angle , Silver #230 (CG - CI - 3)

, 1 0° 1.1 0.50 0.36 0.21 0.050

-10° 0.98 0.53 0.38 0.22 0.050

-20° 0.90 0.48 0.34 0.13 0.044

-30° 0.64 0.33 0.28 0.14 0.034

-40° 0.50 0.2b 0.22 0.088 0.021

-60° 0.20 0.11 0.070 0.034 0.011

Cutoff Angle - >65°

Wide Angle, “C u Black #234 (CG-C-2)

0° 1.1 0.82 0.48 0.19 0.050 0.029 0.016

-10° 1.4 0.72 0.42 0.19 0.042 0.024 0.014

-20° 0.75 0.4l 0.25 0.11 0.025 0.012 - -30° 0.19 0.13 0.10 0.048 0.013 - - -40° 0.1b O.058 0.026 0.014 - - Cutoff Angle ->35°
'

c

...

.

•
Table III (Continued)

a. Specific Intensity per Square Inch (Continued)

Angle of Angle of Divergence

Incidence 0° l74° 1/2° 1° 2° ~ 3°~ 4° 5° o

°

Wide Angle, "C 11 White #246 (CG - 246)

0° 2. 6 1.3 1 . 0 0 ..50 0 ..13

-20° 0 . 53 0.30 0 . 26 0 .,16 0 ., 064

-4o° 0 . 28 0.19 0 . 14 0 .,092 0 .,048

-6o° 0 . 12 0.083 0 . 0o4 0 .,042 0 ..028

Cutoff Angle ->85°

Wide Angle ?

t4C

w White (NATC -2)

0° 0 . 79 0.33 0 . 24 0 .,11 0..033

-10° 0 . 68 0.30 0 . 22 0 .,098

-20° 0 . 18 0.094 0 . Obi 0 ..037

-4o° 0 . 054 0.037 0 . 02 7 0 .,019 0 ..013

-60° 0 . 023 0.017 0 . 0l4 0 ..0093 0 ..0077

-80° 0 . 0073 - - - Cutoff Angle ->85°

Flat Top, Silver #2250 (CG-0N-2A)

0° 0.62 0.69 0.50 0.18 0.096 0.044 0.029 0.019

-10° 0.51 0.35 0.22 0.11 0.048 0.026 0.019 0.010

-20° 0.084 0.076 0.050 0.033 0.021 0.018 0.012 0.0097

-30° 0.021 0.015 0.012 0.0092 - - - - Cutoff Angle - Approximately 45°

Flat Top, Silver #2250 (CG-ON-2)

0° 0.58 0.48 0.33 0.16 0.076

-10° O .38 0.28 0.19 0.12 0.048

-20° 0.076 0.070 0.053 0.033 0.021

-30° 0.015 0.012 0.010 0.0037 0.0068

Cutoff Angle - Approximately 45°

Wide Angle, Flat Top, Silver #2270 (CG-0G-4A)

0

° 1.6 0.90 0.55 0.22 0.092 0.048 0.028 0.021

- 10 ° 1.0 0.66 0.39 0.21 O.O 76 0.029 0.021 0.014

- 20 °

.. 0.60 0.42 0.25 0. 14 0.067 0.033 0.020 0.012

-40° 0.18 0.18 0 . l4 0.088 0.042 0.022 0.020 0.015

-6 0

° 0.033 0.029 0.0 20 0.014 0.011 — -70° 0.00870.005b 0.0056 - - - - Cutoff Angle ->85°
(
Table III (Continued)

a. Specific Intensity per Square Inch (Continued)

Angle of Divergence

Incidence 0° 1/4° 1/2° 1° 2° 3° 4° 6°

Wide Angle, Flat Top, Silver #2270 (CG-OG-4)

0° 1.8 1.4 1.1 0.53 0.26

-20° 1.3 0.96 0.72 0.42 0.20

-4o° 0.42 0.33 0.26 0.22 0.12

-6o° 0 . 0'/6 0.067 O.Obl 0.042 0.028

Cutoff Angle ->85°

Wide Angle, Flat Top, White (NATC-3

)

0° 0.66 0.57 0.35 0.23

-10° 0.68 0.49 0.28 0.20

-20° 0.42 0.33 0.22 0.16

-4o° 0.15 0.13 0.11 0.068

- 60 ° 0.02b 0.022 0. 01o 0.014

Cutoff Angle ->85°

V/ide Angle, Flat Top - (CG-EA)

0° 0.27^ 0. 040

-4o° O.066 0.019

-6o° 0.014 0.0066

-80° 0.0039

Cutoff Angle ->85°

.at Top, Silver #2200 (1949-1)

0

° 0.76 0.68 0.44 0.22 0.081 0.056 0.045 0.026 0.019

10° 0.47 0.34 0.24 0.14 O.054 0.034 0.021 0.016 0.011

20° 0.051 0.035 0.025 0.021 0.017 o.oi4 0.011 0.011 - 25° 0.013 0.0099 - - - - - - Cutoff Angle - Approximately 45°
•

'

• •
- 4 -

Table III (Continued)

a. Specific Intensity per Square Inch (Continued).

Angle of Angle of Divergience

Incidence! 0

° 174^ 1/2° 1° 2

° 3° 4

° 50 6°

Standard, Signal Silver #244 (1949-3

)

0° 1.41

,

0.44 0.34 0.20 0.070 0.043 0.023 O.023 0.023

-10° 1.29 0.6l 0.32 0.20 0.062 0.042 0.026 0.022 0.021

-20° 0.26 0.12 0.11 0.073 0.044 0.031 0.026 0.019 0.015

-30° 0.032 0.020 0.019 0.015 0.014 0.0'i2 0.012 0.010 0.0097

-40° 0.019 0.012 0.11 0.0092 0.0081 - - - - +10° 1.39 0.43 0.32 O.lo 0.070 0.037 0.022 0.022 0.019

+20° 0.27 0. L4 0.11 0.078

' 0.051 0.040 0.037 0.020 0.017

+30° 0.032 0/020 0.020 0.019 0.015 0.015 0.014 0.014 0.012

+40° 0.019 0.011 0.0098 0.0096 0.0092 0.0097 0.0081 0.0081 0.0081

Cutoff Angle - Approximately 60°

n Vinyl it

e

i Base*11 Silver ON CTn 1!— 2)

0° 1.5 0.73 0.36 0.20 0.070 0.042 0.028 0.024 0.019

-10° 0.32 0.43 0.32 0 . 14 0.054 0.040 0.029 0.025 0.021

-20° 0.24 0.13 0.094 0.051 0.032 0.024 0.022 0.017 0.015

-25° 0.089 0.026 0.01D

-30° 0 . o44 0.031 0.022 0.013 0.012 - - +10° 0.80 0.39 0.24 0.16 0.073 0.042 0.034 0.024 0.021

+20° 0.19 0.11 0..089 0.056 0.037 0.031 0.026 0.025 0.021

+25° 0.11 0.034 0.028

+30° 0.034 0.029 0.022 0.015 0.012 0.012 - - Cutoff Angle - Approximately 75°
’ . . « t • i

. : :

. .

•

.

. -

,

.

(

K
- 5

-

Table III (Continued)

b. Luminance Factor

Angle of Angle of Divergence Incidence 0° o -X

i

—

1/2® 1° __2° .3°

St andard

? Signal Silver #241+ (CG - CA -- 1)

0° 950 310 230 150 53

-10° 750 3^0 2o0 loO 48

-20° 110 80 66 52 40

-30° 22 12 9.4 7.9 5.7

-40° 15' 8.0 6 .

6 .

5.1

Cutoff Angle - Approximately 60°

Standard t

' l C' 1 Black #226 (CG-CI-1)

0° 710 370 310 230 100

-10° 450 230 190 110 53

-20° 84 36 29 17 8.0

Cutoff Angle - Approximately 30°

Wide Angle, Silver #230 (CG - CI-3)

0° 520 230 160 93 23

-10c 46o 250 180 100 24

=*20° 470 250 180 91 23

-30° 390 200 170 88 21

- 40 ° 380 200 170 69 17

- 6 o° 360 210 130 64 21

Cutoff Angle - 0 A

CO 0

Wide Angle, UC " Black #234 (CG - C - 2)

0° 500 370 220 87 23 13 7.4

10° 640 3*+0 200 90 20 11 6 . 6

20° 390 210 130 56 13 6.4 - 30° 120 80 6l 29 8.0 - - 40° 130 - 45 21 11 - - Cutoff Angle - .Approximately 45°

Table III (Continued)

b. Luminance Factor (Continued)

Angle of Angle of :Divergence

Incidence 0° i74° l/2® i° 2° 3° 40 T° b°

Wide Angle, UC

!,l White i7246 (CG - 246

)

0° 1200 610 460 230 53

-2C° 300 150 130 84 33

-4o° 210 150 110 72 38

-60° 220 ibO 120 78 54

Cutoff Angle - >85°

Wide Angle, UC' White (NATC-2)

0° 360 180 110 50 15

-10° 320 l4o 100 46

-20° 94 48 32 19

-40° 4l 28 21 15 10

-60° 42 31 25 18 15

-80° llQ. - Cutoff Angle - >35°

•

Flat Top, Silver #2250 (CG-CN-2A

)

0° 280 310 230 83 43 20 13 8.3

-10° 240 170 100 53 23 13 9.2 4.9

-20° 43 4o 26 17 11 9.5 6 . 5 5.2

-30° 13 8. 8 7.4 5.6 - - - Cutoff Angle - Approximately 45°

Flat Top, Silver #2250 (CG - ON - 2)

0° 26C 220 150 74 35

-10° 170 130 90 55 2°

-20® 39 3b 27 19 11

-30° 9 .3 7.4 6.3 5.3 4.2

Cutoff Angle - Approximately 45°

Table III (Continued)

b. Luminance Factor (Continued)

Angle of

Incidence

Angle of Divergence

0° 1/4° 1/2° 1° 2

P 3° 4° 5°

Wide Angle , Flat Top, Silver #2270 (CG - 0G -4A)

0° 710 410 250 100 42 22 13 9.8

-10° 4^0 310 190 100 36 14 10 6.9

- 20° 310 220 130 74 35 17 11 6.5

-40° 140 140 110 69 33 18 17 13

-60° 59 54 38 28 22 - - “70° 34 22 22 - -- - - -

Cutoff Angle ->85°

Wide Angle , Flat Top, Silver #2270 (CG - 0G - 4)

0° 810 620 490 240 120

-20° 670 490 370 220 100

-4o° 330 250 200 180 93

-60° l4o 120 110 78 54

Cutoff Angle ->85°

Wide Angle, Flat Top, White (NATC - 3)

0° 300 260 160 110

-10° 320 2 30 130 0)4. -20° 220 170 110 85

-40° 120 99 83 54

-6o° 47 40 30 27

Cutoff Angle ->85°

Wide Angle, Flat Top

0° 120

-40° 51

-60° 24

-80° 58

(CG - EA)

18

14

11

Cutoff Angle ->85°

Table III (Continued)

b. Luminance Factor (Continued)

Angle of Angle of Divergence

Incidence 0° 174^" l72® 1° 2° 3° 4° 5° T'

Flat Top, Silver #2200 (19^9 - 1)

0° 340 310 200 99 37 p6 21 12 8.7

10° 220 lbO 110 67 25 16 9.6 7.6 5.1

20° 26 18 13 11 8.4 7.3 5. 5 5.5 - 25° 7. 3 5.4- - - - - - -

Cutoff Angle - Approximately 45°

Standard, Signal Silver #244 (1949 - 3)

0° 640 200 160 93 32 22 13 10 10

-10® 600 280 150 95 29 20 13 10 10

-20° 140 62 55 38 23 lb 14 10 8.1

-30 c 20 12 11 9.2 3.4 7.8 7.5 d.5 8.3

-40° l4 9.2 8.9 7.3 o.4 - - +10° 550 200 150 73 33 17 10 10 8.6

+20° i4o 70 55 4o 2b 20 18 10 3.5

+30° 20 12 12 li 9.0 8.9 8.3 8.2 7.1

+4o° 16 8.8 7.6 7.5 7.0 7.2 5.9 5.8 5.8

Cutoff Angle - Approximately 60°

*

Vinyl ite Base 11

, Silver (1949 - 2)

0° 690 330 160 100 32 19 13 11 8.5

-10° 380 200 150 b4 2b 19 14 12 10

-20° 130 75 48 2b 17 12 12 9.1 8.3

-25 50 16 9.1

-30 2 7 19 13 8.1 7.4 - - - + 10 380 180 110 03 34 20 16 11 9.8

+ 20 98 54 46 28 19 15 13 12 11

+ 25 60 19 15

+30 21 18 13 9.2 7.4 7.3 - -

Cutoff Angle - Approximately 75°

1

Table IV

Retroref lectors Manufactured by

Keflexite Corporation

a. Specific Intensity per Square Inch

Angle of Angle of Divergence

Incidence 0° 1/4° 1/2 ® ] 0 2 °_ 3

c 4° 5°

C69R - Clear - (CG - Clear)

0 ° 3.3 0.89 0.23 0.046 0.011

- 10 ° 2.2 0.60 0 . 1

1

' 0.021 0 . 00o4

- 20 ° 0.13 0 . Odd O.C'69 0.03k 0.0084

-30° 0.013 0.0076 0.0031 0.0044 0.0029

Cutoff Angle - Approximately 33°

C69R - Clear - (CG - C 69R)

0 ° 4.7 1.6 0.34 0.15 0.057 0.016

-10° 1.4 0.78 0.22 0.092 0.047 0.0091

-20° 0.20 0.097 o.o43 0.025 0.021 0.012

Cutoff Angle - Approximately 33°

C56R - Clear (CG - C56R)

0° 0.11 0 071 0.045 0.031 0.018 0.015 0.012

- 10 ° 0.033 0.042 0.038 0.020 0.013 0.0076 - -20° O.O'M-3 0.021 0.013 0.0071 - - - - 30 ° 0.029 0.012 0.0061 - - - - -4o° 0.011 0.0058 - - - -

Cutoff Angle - Approximately 43°

C 69 Met - Clear (CG - C69 Met)

0° 28 18 4.2 0.77 0.18 0.090 0.055 0.033

-3° 11 6.0 1.9 0.22 0.044 0.019 - -

- 7 . 5° 4.5 2.0 O .69 0.17 0.046 0.025 - -

- 10 ° 0.69 0.48 0.18 0.061 - ~ - -

- 12.3 0.10 0.061. 0.036 - - - - Cutoff Angle - Approximately 13°
I
2

1

Table IV (Continued)

a. Specific Intensity per Square Inch

Angle of

Incidence

Angle of Divergence

0° 1A° 1/2° 1° 2° 3° 4° 5° 6°

C56 Met - Clear (CG - C56 Met)

0° 0.56 0.49 0.39 0.27 0.25 0.25 0. 13 0 . 082

y 0.24 0.20 0.22 0.17 0.10 0.046 0. 027 0 . C14

-7.5° 0.28 0.20 0.15 0.095 0.056 0.030 - - -10° 0.062 0.029 - - - -

Cutoff Angle - Approximately 12°

C - WA - 0.070“ (1949 - -C - WA)

0° 0.34 0.14 0.13 0.039 0.025 0.023 0.013 0.017 0.017

10° 0.35 0.18 0.074 0 .C 30 0.020 0.020 0.016 0.016 0.016

15° 0.21 0.035 0.020

20° 0.15 0.12 0.084 0.050 0.022 0.017 0.014 - — 25° 0.078 0.037

30° 0.043 0.033 0.030 0.023 0.019 0.016 - - -

\ I

^ Cutoff Angle - Approximately 35°

1

1

]

1

]

J

1

]

- 3

- Table IV (Continued)

b. Luminance Factor

Angle of Angle of Divergence

Incidence 0° 1/4° 1/2° 1° 2® 3° 4° *5® 6°

C69R - Clear (CG - Clear)

0° 1500 400 120 21 4.9

-10° 1000 280 68 9.3 3.0

-20° 770 46 35 18 4.4

-30° 7.9 a6 3.1 2.7 1.8

Cutoff Angle - Approximately 3 5°

C69R (CG - C69R)

0° 2200 720 240 66 26 7.1

-10° 660 370 100 43 22 4.3

-20° 100 50 23 13 11 6 .

Cutoff Angle - Approximately 35°

C56R - Clear (CG - C56R)

0° 48 32 21 14 8.3 6.

5.3

-10° 2 5 20 18 9.4 6 .

3.6

-20° 23 11 6.7 3.7 - - - -30° 18 7.1 3.7 - - - - -40® 8.6 4.5 - - - -

C utofAngle - Approximately 45°

C69 Met - Clear (CG - C 69 Met)

0° 12500 8100 1900 350 82 4l 25 15

-5° 5200 2800 860 100 20 8.6 - - -7.5“ 2100 930 320 80 21 12 - - -10° 320 220 85 29 - - - - -12.5® 50 29 17 - - - - -

Cutoff Angle - Approximately 13°

C56 Met - Clear (CG - C56 Met)

0® 250 220 180 120 110 110 60 38

“5° 110 90 100 80 48 21 13 6.4

-7.5° 130 94 68 44 26 14 -» -10® 29 14 - - - - - Cutoff Angle - Approximately 12°

Table IV (Continued)

b. Luminance Factor (Continued)

Angle of

Incidence

(D

i

—

<c! of Divergence

0° 7%° i—

i \|IV 0 1

° 2

o 3° 4° 5° b

C- WA - 0. 070" (1949 - C - WA)

0° l6o 64 60 18 11 10 8.3 7.9 7. 6

10 ° 140 83 35 14 9.4 9.1 7.3 7.3 7. 3

15 ° 100

43

17 9.9

20° 76 6l 2b 11 8.4 7.1

25° 43 20

3 0° 26 20 18 14 11 9.0 - - Cutoff Angle - Approximately 35°
((
1

Table V

Retroref lectors Manufactured by

catapnote Corporation

a. Specific Intensity

Angle of Angle of Divergence

Incidence 0° w 1/2° 1° 2° 3° 4° 5° 6°

#1A Crystal (3/4u diameter)*

0° 3.6 2.7 1.1 0 .,14 0.034

-10° 2.5 2.7 0.87 0 .,42 0.053

-20° l.l 0.88 0.83 0 .• 71 0.22

“30° 0.31 0.22 0.28 0 .-30 0.16

Cutoff Angle - Approximately 35c>

#3 Crystal (3 A" diamet er )**

0° 1.5 0.95 0.63 0..21 0.064

-10° 1.2 0.d5 0.52 0 ..17 0.057

-20° 0.88 0.83 0.54 0 .,20 0.034

-30° 0.29 0.24 O.23 0 ,-19 0.13

-40° 0.091 0 . 044 o.o44 0 ..048 0.034

Cutoff Angle - Approximately 55°

* Average of 4 units

** Average of 3 units

Table V (Continued)

b. Specific Intensity per Square Inch

Angle of Angle of Divergence

Incidence 0° 1/4° 1/2° 1° 2° 3° ~4° 5° ~ p°

#1A Crystal*

0° 8.2 6. 1 2.5 0.33 0.077

-10° 5.7 6. 1 2.0 0.96 0.12

-20° 2.6 2. 0 1.9 1.6 0.50

"30° 0.70 0 . 50 0.63 0.69 0.37

Cutoff Angle - Approximately 3 5°

#3 Crystal**

0

° 4.2 2.7 1.3 0.60 0.13

- 10 ° 3.3 2.4 1.5 0.49 0.16

- 20 ° 2.5 2.4 1.5 0.53 0.096

-30° O.83 O .69 0.b4 0.53 0.33

-4o° 0.26 0.12 0.12 0.14 0.096

Cutoff Angle - Approximately 55c

* Average of 4 units

** Average of 3 units

Table V (Continued)

c. Luminance Factor

Angle of Angle of Divergenc e Incidence 0° 1/4° L/2 V 1° 2^ 3° "4 ° ~5° 6

°

#1A Crystal*

0° 3300 2800 1100 150 35

-10° 2600 2300 930 450 57

-20° 1300 1000 970 8^0 260

-30° 430 300 390 420 230

Cutoff Angle - Approximately 35*

#3 Crystal**

0° 1900 1200 800 270 81

-10° 1500 1100 090 230 76

-20° 1300 1200 780 300 50

-30° 500 420 390 330 23k

-4o° 200 96 96 110 77

Cutoff Angle - Approximately 55*1

* Average of 4 units

** Average of 3 units

Table VI

Re troref lectors Manufactured by

Persons-Majestic Mfg. Co.

a. Specific Intensity*

Angle of Angle of Divergence

Incidence 0° l/4° 1/2° 1° 2° 3° 4° ~5° 6

°'

Clear (3/4tt diameter)

0° 1.6 1.2 0 . 6$ 0.13 0.051

-10° 1.7 1.3 0.45 0.19 0.053

- 20° 1.6 1.2 0.76 0.19 0.057

-30° 1.3 0.91 0.97 0.37 0.051

-40° 0 . 0A2 0.030 0.026 0.17 -

Cutoff Angle - Approximately 45°

b. Specific Intensity per Square Inch*

Clear

0° 3.4 2.4 1.4 0 . 2 $ 0.11

-10° 3.7 2 . $ 0.96 0.40 0.11

- 20 ° 3.4 2.4 1.6 0.41 0.12

-30° 2 .$ 1.9 2.1 0.79 0.11

-40° 0.090 0.064 0.054 0.035 -

Cutoff Angle - Approximately 45°

c. Luminance Factor*

Clear

0

° 1500 1100 660 130 50

-10° 1700 1300 450 190 53

- 20° 1700 1360 $40 210 63

-30° 1700 1200 1300 4$0 67

-40° 69 50 42 2 $ -

Cutoff Angle - Approximately 45°

* Average of 2 units

Table VII

Retroreflectors Manufactured by

Grote Manufacturing Co., Inc.

a. Specific Intensity

Angle of Angle of Divergence

Incidence 0° 174^ 1/2° 1° 2° 3° 4°

Type 105 - Clear - (2 7/3h diameter)

0° 160 98 33 3.4 0.91 0.46 0.25

-10° 120 83 28 3.9 0.44 - — -20° 68 58 28 2.5 0.35 - ~ -30° 6.9 5.8 2.5 0.29 - - - -b0° 1.4 1.4 0.55 0.24 — - -50° Q.49 0.41 0.29 - - - - Cutoff Angle - Approximately 55°

b. Specific Intensity per Square Inch

Type 105 - Clear

0° 26 16 5.3 0.55 0.15 0.075 0.041

-10° 19 13 4.5 O .63 0.070 - - -20° 11 9..3 4.5 0.40 0.056 — -30° 1 .,1 0 ., 9^ 0.40 0.046 - _ — -40° 0 ..23 0 .,22 0.088 0.038 — — _ -50° 0 ..0791 0 ., 066 0.046 - - - -

Cutoff Angle - Approximately 55°

nPlate M-Silver

0

° 0.45 0.23 0.21 0.22 0.14 0.095 0.064 0.045

- 10° 0.29 0.24 0.17 0.073 0.032 0.014 0 . 0^92 0.0063

- 20° 0.028 0.24 0.020 0.011 0.0070 0.0040 - -30° 0.0059 0.0038 - - - -

'

Cutoff Angle - Approximately 30°

Table VII (Continued)

c. Luminance Factor

Angle of Angle of Divergence

Incidence 0

° l'A® 1/2 ® — 1“ 2

o 3° 4°

Type 105 - Clear

0

° 12000 7100 2400 250 66 34 19

-10° *9100 6200 2100 300 33 - - - 20° 4800 2300 200 29 - 0

-3A® ©70 570 240 28 - — -W° 180 170 68 30 - - - -50° 87 73 51 - - - - Cutoff Angle - Approximately 55c

“Plate 11 -

0°

Silver

200 130 95 98 65 29 21

-10° 140 110 81 34 15 6.7 4.4 3.0

-20° 15 12 10 5.7 3.6 2.1 — _ -30° 3.6 2.3 - - ~ - - Cutoff Angle - Approximately 30°
. . ... ... .. .

'
Table VIII

A Ref lectorized Paint Manufactured by

Prismo Safety Corporation

a. Specific Intensity per Square Inch

Angle of Angle of Divergence

Incidence 0° iAy 1/2° 1° 2° 3

° 40 5

° 6°

0° 0.037 0.032 0.026 0.022 0.019 0.014 0.010 0.0084

-10° 0.037 0.025 0.022 0.021 0.016 0.018 0.011 0.0079

-20° 0.032 0.029 0.027 0.023 0.018 0.013 0.0039 0.0039

-40° 0.030 0.022 0.018 0.013 0.015 0.013 0.010 0.0076

-60°

-80°

0.019

0.0069

0.013 0.012 0.010 0.0073 0.0057 0.0043 0.0023

b. Luminance Factor

0° 17 14 12 10 8.6 6.2 4.8 3.8

-10° 15 12 11 10 7.6 5.

5.2 3.8

-20° 16 15 14 12 9.6 6.9 4.7 4.3

-40° 23 17 14 14 12 11 8.2 6.3

-6o° 35 24 23 19 14 12 8.9 5-9

-80° 104

Cutoff Angle - Approximately 80 °

SCHEMATIC ARRANGEMENT OF RETROREFLECTOR TEST RANGE

NBS Test 21P-16/54 Figure 1

CM n

i—

*

H

u*.

/J

o,

J

i

'j

oTS?u.

VO O

cr °

Ui

<r »§

UMJ

NBS

Test

21Pr

16/54

Figure

PER SQUARE INCH

AS. A FUNCTION OF ANGLE OF INCIDENCE

at jO° Divergence ... VT.\.

Of Several Representative Re troreflectors

• Stimsonite No. 19

© Grotelite No. 105

A Seotchlite Wide Angie - Flat Top Silver *2270

DReflexite, Type C69Met

OCataphote Ho. 3 Crystal

-i Prismo Reflective PaintAngle of Incidence

s

Figure 3
I

\
SPECIFIC INTENSITY PER SQUARE INCH

AS.A-FjPNCTIOW~OF ANGLE OF DIVERGENCE

At 0° Incidence

St ims onite No. 19

© Grotelite No. 105

& Scotchlite, Wide Angie

Flat Top Silver tf 2270

Reflexite, lype C698fet

Q Gaiaphote No. 3 Crystal-

+ Prismo Reflective Faint

Angle of Divergence

Figure 4



Figure 6

Figure 7

I T T SPECIFIC Zr^'SITTIW.SQW^ —- AS A-FUNGTIGN °F ANGLE CF -BIVERGF.fCE — at 0° incidence

! of Re troreflectors Manufactured by

Scotchlite Reflective Products Bivisi on Minnesota Mining and Manufact ur i ng Co.

Standard, Signal Silver

4

- *244

© Standard G" Black *226

A Flat Top, Silver *225

Q

G" Black

*234

C" White

*246

-+- Wide Angle, Silver *230

A Wide Ang le. Flat Top,

IVide Jingle

Silver *2270

White

Angle of Di verge nee

i^./4

' r r

: - * --

i r i:

Figure 8



Figure 10

Figure 11
<
Figure 12
I


Figure 14



Figure 16

Figure 17

Figure 18

THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods

for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials,

devices, and structures; advisory services to Government Agencies on scientific and technical

problems; invention and development of devices to serve special needs of the Government; and the

development of standard practices, codes, and specifications. The work includes basic and applied

research, development, engineering, instrumentation, testing, evaluation, calibration services, and

various consultation and information services. A major portion of the Bureau’s work is performed

for other Government Agencies, particularly the Department of Defense and the Atomic Energy

Commission. The scope of activities is suggested by the listing of divisions and sections on the

inside of the front cover.

Reports and Publications

The results of the Bureau’s work take the form of either actual equipment and devices or published papers and reports. Reports are issued to the sponsoring agency of a particular project

or program. Published papers appear either in the Bureau’s own series of publications or in the

journals of professional and scientific societies. The Bureau itself publishes three monthly periodicals, available from the Government Printing Office: The Journal of Research, which presents

complete papers reporting technical investigations; the Technical News Bulletin, which presents

summary and preliminary reports on work in progress; and Basic Radio Propagation Predictions,

which provides data for determining the best frequencies to use for radio communications throughout

the world. There are also five series of nonperiodical publications: The Applied Mathematics

Series, Circulars, Handbooks, Building Materials and Structures Reports, and Miscellaneous

Publications.

Information on the Bureau’s publications can be found in NBS Circular 460, Publications of

the National Bureau of Standards ($1.00). Information on calibration services and fees can be

found in NBS Circular 483, Testing by the National Bureau of Standards (25 cents). Both are

available from the Government Printing Office. Inquiries regarding the Bureau’s reports and

publications should be addressed to the Office of Scientific Publications, National Bureau of Standards, Washington 25, D. C.

I*

I