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College of Optometry Theses, Dissertations and Capstone Projects

8-24-1974

The affects of tinted lenses on visual dection of features in a The affects of tinted lenses on visual dection of features in a

snowy environment: A computer simulation snowy environment: A computer simulation

Lynn Burge Pacific University

Recommended Citation Recommended Citation Burge, Lynn, "The affects of tinted lenses on visual dection of features in a snowy environment: A computer simulation" (1974). College of Optometry. 372. https://commons.pacificu.edu/opt/372

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The affects of tinted lenses on visual dection of features in a snowy environment: The affects of tinted lenses on visual dection of features in a snowy environment: A computer simulation A computer simulation

Abstract Abstract The affects of tinted lenses on visual dection of features in a snowy environment: A computer simulation

Degree Type Degree Type Thesis

Degree Name Degree Name Master of Science in Vision Science

Committee Chair Committee Chair Frank Thorn

Subject Categories Subject Categories Optometry

This thesis is available at CommonKnowledge: https://commons.pacificu.edu/opt/372

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THE AFFECTS OF TINTED LENSES

ON VISUAL OECTION OF

FEATURES IN A SNOWY ENVIRONMENT:

A COMPUTER SIMULATION

THE AFFECTS OF TINTED LENSES ON VISUAL DETECTION

OF FEATURES IN A SNOWY ENVIRONMENT:

A COMPUTER SIMULATION

Lynn Burge

Submitted in partial fulfillment of the requirements for the degree

Doctorate of Optometry

August 24, 1974

Approved by Advisor

ACKNOWLEDGMENTS

I wish to thank Dr. Frank Thorn for

his help and guidance in the prepara­

tion of this paper. Also, special

thanks to Dennis Olson of the Pacific

University Computer Center .

TABLE OF CONTENTS

INTRODUCTION

HYPOTHESIS AND THEORY

PROCEDURE AND PROGRAMMING

RESULTS . . .

Table I - A & B Luminous Contrast

II - Color Contrast Enhancement

III - Color Distortion in CIE Space

DISCUSSION

BIBLIOGRAPHY

APPENDICES

A - Listing of Computer Ratios Programmed

B - Luminous Contrast and Ratio # 2

C - Spectral Transmission Curves . .

1 1 3 5

6-7 8

9

10

12

14 15 17

INTRODUCTION -'

A computer was used to anaiyze various colored tints

of sunglasses to, theoretically, see if any special tint

would enhance contrast on snow .

Any appreciable increase in contrast could make sudden

changes in elevation such as crevasses, fissures or ditches

easier to detect by people driving or skiing on snow . A fast

skier needs as much advance warning as possible for changes

in snow elevation. This situation is extremely important for

the conditions of an "arctic whiteout" where all of the snow

features appear to have the same whiteness. 'Ibis condition

is represented by uniformly overcast sky .

HYPOTHESIS AND THEJORY

Several assumptions have to be made to treat this

problem by mathematical procedures. The basic assumptions

followed were those set forth by Wyszecki .1

The "arctic whiteout" is represented by a uniform

overcast sky and a completely diffuse reflecting snow sur-

face .

1G . Wyszecki, L._Opt. Soc. Am., Vol. 46 (No . 3), 1956.

1

The sudden changes in elevation considered dangerous

to a driver or skier are represented in Figure One . Type

2

(1) is a ditch with a unit width and a depth of 1 times the

width . Type (2) is a 11crevasse11 with unit width and "infinite"

depth . Type (3) is a "step" of unit height . Type (4) is a

depression represented by the angle�. The step, ditch, and

crevasse as represented have infinite lengths; in other words

their lengths are many times longer than their widths .

The observer sees the snow surface from an angle$ in Figure One. This angle q, of about 27° (Tan + = 0 . 5)

compares to a distance between the observer and snow edge

of about twice the height of the observer. This is consid­

ered to be the lowest limit at which a driver or skier should

detect an elevation change.

An observer looking at angle f will only be able to

detect a change in elevation if some surface elements appear

to be perceptably different in brightness or chromaticness

from the horizontal surface of the dangerous feature . It

would be expected that the surface hollows would be darker

and appear bluer compared to the reference surface because

only parts of the overcast sky illuminate the interior sur­

faces and also because of the inter-reflections between the

walls of the hollows .

Wyszecki goes into a detailed explanation of the

formulas showing the spectral reflectance of snow (p) and

luminous ratios [r(s)) as functions of wavelengths. These

formulas are listed in Figure One alongside of the respect-

ive hollows they represent. Figure Two shows the resultant

graph of the above formulas. The spectral reflectance of

the snow surface (p) immediately beneath the observer is

3

compared with the reflectance r(s) of the point in the hollow

he is observing. This forms a contrast ratio.

The graph in Figure Two leads to the hypothesis that

a shift to a higher wavelength or towards the red spectrum

will increase contrast. This is illustrated by exaggerating

the contrast ratio as in Figure Three. Contrast is defined

as p-r . It can be seen that p decreases rapidly and p-r p

decreases at a much slower rate. Thus as a point is chosen

further to the right on the graph the contrast ratio increases.

PROCEDURE

The four hollow conditions were analyzed on a computer

for nine tinted lenses. Ratios were programmed to anlyze

p (�) and r (�) functions to compare the luminance and

chromaticity of the observed colored surfaces.

4

CD ru ( s) = (A�) [A1 Co sh (ks)+Az . Siri H . (ks]

0.2

® : , __

®

FIG. 1. Cross sections of four types of sudden chan"es of elevation in a snow field. · 0

400 600

;i.· [mµ.]­Frc. 2. Spectral reflectance of snow and luminance·n

functions of wavelengths. The cun:es indicated by 0, 11;.1 3, 41, 4z represent p(f.), ru(f.), etc_ ;

p

r

I ! !

a.! bl__ A

Fij . .3. Coriira.sT Ra..t1·0

rz(s) ;;:::

r3(�) =

r4 (s) =

A0 = 2 cosh (kl)+k[l+(l+p) sin h (kll} .

A1 =

Az =

p (Cl+p) cosh (kl) +_ k sin h (klj -p((l+p) sin (kl) + k cosh (klJJ

1: k = (1-p) 2

r11 O) Ditch t;..., 0.5

(1-k) exp (-ks)

1 = 1.0 1 = 2.0

0. Sp L 0. Sp (l+p) (1- Cos.) (1 +cos� �

2 . . p sin a/ (1-p cos2 a)

+

FIGURE 4 Color of Snow Surface viewed through Tinted Lenses 4b

900 900 . . .,- . . I ,...., I .

- '20 ,, 525

515 , / . 530 � . 800 800

r 5� l I I "' � OJ I ,..,, 540 " .... \i'l.. M&

I I I '' I I I 5!50

I I roo 700

'I 5

' .600

500

I ' .500

y 495

.400

� - ' w _:;oo 490-••

.200

-480

.100 �

475

-

000 I h

§

.... '! 555

I I 580 I " .... I I I 1\565 I I I I • I

I I I I j I I

I I I I

I

1 or I ,, I I

� I I I

I

I

I

I I

I I

I �10 " •

-

41& ' 460" I 45!1 � 4�40-� ...... I

420 -x

0 Poloroid Neutral A B&L Smoke # 4

I

8 Cool Ray blue/green X Doc # 2

I

I I M

I I

I

EBAO Rose Smoke, medium O Nov C 6 Poloroid Yellow CJ Wratten 23 X Wratten 16 lP (no filter)

"" I

I

.....

•ro j ��r. • ,.,.580 I I ! l I � i I H

I ·;-., SIS

� [± �-+ :f�s.c ;: .. .. I ·- I I

( I I �

I I I I I I •

I

I I _,...

I �

I

i I

-·

....

I I I I i

·-

- 605 :ib 610 1 ... �,&I 620 I ·" 630 I'\.�

� � ��� .. "'°

I I I l I 1

0 R

600

500

y

400

300

200

-- .100

.000 �

5

Using the color mixture functions of the CIE standard

observer representing the eye and the relative spectral

energy distribution S (�) of the overcast sky, and the CIE -

tristimulus values X, Y the CIE - chromaticity coordinates

x, y may be calculated for each given p (�) and r (,\) condi-

tion. When tinted lenses of spectral transmission 'YC/t) are

used for sunglasses the same procedure is performed for the

functions,...(�) p (�) and 1" (�) rs (�) .

RESULTS

The spectral transmission curves of each tinted lens

are shown in Appendix C. Table One represents the luminous

contrast ratios for nine tinted lenses for each of the snow

elevation conditions. Columns 3 through 9 show the lumin-

ance difference4 Y = Yp - Yr relative to the luminance Yp

.

Table Two represents color contrast enhancement . The

apparent color contrast enhancement between the snow surface

and hollow feature is shown by � = x p - X.:r and y = y - y . p r

Table Three shows color distortion in CIE color space.

Color distortion is how the tinted lenses change perceived

color. This calculation is shown by x shift = X (filter) -p

xp (no filter); y shift = Yp (filter) - Y (no filter); p color shift = J X�h+ Y�h The color of the surface of the

snow viewed through the various tinted lenses is shown in

Figure 4, page 4b .

TABLE IA LUMINOUS CONTRAST Illumination: Heavy Overcast

(1) (2) (3) (4) (5) Elevation Conditions Rl-Ll Rl-L2 Rl-L3

Wratten 23 .3690 .3963 . 4114

Wratten 16 .3607 .3882 .4038

Doc 2 .3598 . 3873 .4029

Polaroid Yellow .3564 .3841 .3999

AO Rose Smoke, Medium .3557 .3833 .3992

Noviol C . 3542 . 3820 .3980

B&L Smoke # 4 .3527 .3804 .3965

Cool Ray blue/green .3521 . 3798 .3959

No Glass Filter .3517 .3794 . 3955

Polaroid Neutral .3509 .. 3786 .3948

A y = y - y p r ---

y p

(6) (7) R2 R3

.4790 .0208

.4727 .0200

.4720 .0199

.4695 .0196

.4689 .0196

.4678 .0194

.4667 .0194

.4661 .0193

.4659 .0192

.4652 .0191

(8) R4

.1982

.1917

.1911

.1884

.1879

.1868

.1857

.1851

.1848

.1842

°'

TABLE IB

(1) (2) Elevation Conditions

Wratten 23 Delta Y

Wratten 16

Doc 2

Polaroid Yellow

AO Rose Smoke, Medium

Noviol C

B & L Smoke # 4

Cool Ray

No Glass

Polaroid Neutral

LUMINOUS CONTRAST Illumination: Light Overcast

(3) Rl-Ll

.3685

.3603

.3591

.3562

.3553

.3541

.3525

.3518

.3513

.3506

(4) Rl-L2

.3958

.3879

.3866

.3839

.3830

.3817

.3802

.3796

.3791

. 3 783

(5) Rl-L3

.4109

.4035

.4023

.3997

.39'89

.3977

.3963

.3957

.3953

.3945

(6) R2

.4786

.4725

.4714

.4693

.4686

.4676

.4664

.4659 .

.4653

.4949

(7) R3

.0208

.0200

.0199

.0196

.0196

.0194

.0193

.0193

.0192

.0191

(8) R4

.1978

.1914

.1905

.1882

.1876

.1866

.1854

.1849

.1845

.1339

-.....J

TAB LE II COLOR CONTRAST ENHANCEMENT Heavy Overcast

� = x - x p r y

= y - y p r

Doc No . 2 4 x �y

B&L Smoke No. 4

No Glass Filter

AO Rose Smoke, Med .

Cool Ray, blue/green

Poloroid Neutral

Nov C

Polaroid Yellow

Wratten 16

Wratten 23

Rl-L3 Rl-L2 Rl-L3 R2 R3 R4

.01002 .01029 .01000 .00946 .00059 .00613 .00667 .00692 .00677 .00642 .00039 .00404

.00760 .00781 .00757 .00717 .00045 .00466 .00604 .00629 .00618 .00586 .00035 .00364

.00741 .00761 .00739 .00700 .000445 .00455 . 00652 . 006 77 . 00664 . 00630 . 00038 . 00395

.00727 .00745 .00722 .00683 .00043 .00444 .00327 .00343 .00338 .00320 .00018 .00195

.00711 .00729 .00707 .00669 .00042 .000435 .00436 .00454 .00447 .00424 .00025 .00262

.00701 .00720 .00699 .00662 .00042 .00430 .00652 .00678 .00665 .00631 .00038 .00395

.00524 .00534 .00515 .00436 .00031 .00321 .00195 .00196 .00188 .00177 .00012 .00121

.00381 .00387 .00371 .00351 .00023 .00234 .00340 .00344 .00331 .00312 .00020 .00209

, 0023 7 • 00239 , 00229 • 00216 • 00014 • 00146 I

.00230 .00233 .00223 .00210 .00014 .08141 ':' . 00066 . 00066 . 00063 . 00059 . 00004 . 00041

.00066 .00066 .00063 .00059 .00004 .00041

1

2

3

4

5

6

7

8

9

TABLE III

Color Distortion in CIE Color Space

x shift

Polaroid Neutral -. 0082

B&L Smoke # 4 .0258

Cool Ray blue/green .0357

Doc # 2 .0823

AO Rose Smoke, Med. .0966

Nov C .1252

Polaroid Yellow . 1742

Wratten 16 .2253

Wratten 23 .3343

x shift = �p (filter) �p (no filter)

x shift = Yp (filter) - Yp (no filter)

color shift = \l(x shift�f + (y shift7 illumination = Light Overcast

y shift color shift

.0065 .0105

.0401 .0477

.0822 .0896

-. 0378 .0906

.0914 .1330

.2009 . 2367

. 2135 .2755

.-1719 .2834

.0652 .3406

'°

10

DISCUSSION

The R3 condition has very low luminous contrast; the

other conditions are above incr-emeiit thresholds . However, for

the skier or the pilot corning into this type of condition at

high speed, he must have quick reflexes and any enhancement

of contrast is useful .

This paper is looking for filters and tints which

will maximize contrast. Overall the lenses studied gave

discouraging results in contrast enhancement. Wratten 23

and 16 gave the most enhancement in luminous contrast and

this was only 4-8%. Contrast is enhanced slightly by tints.

This may be useful for someone who needs a racer's edge. For

the casual skier the contrast enhancement would probably not

provide any noticeable improvement .

It is interesting to ask if color contrast offers

assistance in seeing the difference in snow elevations. Color

enhancement is by far the best for the Doc lens . The Wratten

filters, which did good with luminous contrast, destroy color

contrast .

The Doc lenses seem to combine both color contrast

and luminous contrast so that in overall contrast enhance­

ment it was the best lens .

11

We should ask about color distortion. Does the world

look natural or distorted? If it looks unnatural, will off­

color tints effect the involved person's reactions .

The color shift is very great for many of the lenses

which enhance luminous contrast or color contrast . The Doc

lenses have the least amount of color distortion when

compared to the lenses which greatly enhance contrast .

12

BIBLIOGRAPHY

Eastman Kodak Company, .Kodak Wratten Filters for Scientific & Technical Use, 22nd Ed., U.S.A., 1968

Stair., Ralph "Spectral - Transmission Curves," National Bureau of Standards, Circular 471. Washington, Govern­ment Printing Office, 1g4g

Wyszecki, Gunter, "Theoretical Investigation of Colored Lenses for Snow Goggles," Journal of the Optical Society of America, Vol. 46 (12), December, 1956.

APPENDICES

A - Listing of Computer Ratios Programmed

B - Luminous Contrast and Ratio # 2

C - Spectral Transmission Curves

13

APPENDIX A

Listing of Computer Ratios Programmed

Ratio = Luminous contrast ratio = Yp Yr Yp

14

value greater than one indicates contrast enhancement

llY

x r

= y - y p r

Ax ratio = Qx(filter) Ax(no filter)

x shift = x (filter in) - x p x shift = yp (filter in) - y

(no filter) p (no filter) p

Color shift = '1{x shift)2 + (y shift)2

APPENDIX Bl LUMINOUS CONTRAST Illumination: Heavy Overcast

Elevation Conditions Rl-Ll Rl-L2 Rl-L3 R2 R3 R4

Wratten 23 fly .3690 .3963 .4114 .4790 .0208 .1982 Ratio # 2 1 .049 1 .044 1.040 1 .028 1 .082 1 .073

Wratten 16 .3607 .3882 .4038 .4727 .0200 .1917 1.026 1 . 023 1 .021 1 .014 1 .041 1 .037

Doc 2 .3598 .3873 .4029 .4720 .0199 .1911 1 .023 1 .021 1 .019 1.013 1.038 1 .034

Polaroid Yellow .3564 .3841 .3999 .4695 .0196 .1884 1 .013 1 .012 1 .011 1 .008 1.022 1 .019

AO Rose Smoke .3557 .3833 .3992 .4689 . 0196 .1879 Medium 1. 011 1 .010 1 .009 1 .007 1.019 1.017

Noviol c .3542 .3820 .3980 .4678 .0194 .1868 1.008 1 .007 1 .006 1 .004 1 .012 1 .011

B & L. Smoke .3527 .3804 .3965 .4667 .0194 .1857 -No .' fr 1 .003 1.003 1 .002 1 .002 1 .008 1 .005

Cool Ray .3521 .3798 .3959 .4661 .019� .1851 blue/green 1. 001 1 .001 1 .001 1.000 1 .001 1 .002

No glass filter .3517 .3794 .3955 .4659 .0192 .1848

Polaroid Neutral .3509 . 3786 .3948 .4652 . 0191 .1842 .9977 .9979 .9981 .9987 .9962 .9966

I t--' V1 I

APPENDIX B2 LUMINOUS CONTRAST Illumination: Light Overcast

Elevation Conditions Rl-11 Rl-12 Rl-L3 R2 R3 R4

Wratten 23 11 y . 3685 .3958 .4109 .4786 .0208 .1978 Ratio # 2 1.049 1.044 1.040 1.028 1.081 1.072

Wratten 16 .3603 .3879 .4035 .4725 .0200 .1914 1.026 1. 023 1.021 1.015 1.042 1.037

Doc 2 .3591 .3866 .4023 .4714 .0199 .1905 1.022 1.020 1.018 1.013 1.037 1.033

Poloroid Yellow .3562 .3839 .3997 .4693 � 0196 - ·.:1882 1.014 1.013 1.011 1.008 1.022 1.020

AO Rose Smoke .3553 .3830 .3989 .4686 .0196 .1876 Medium 1.011 1.010 1.009 1.007 1.019 1.017

Noviol C .3541 .3817 .3977 .4676 .0194 .1866 1.008 1.007 1.006 1.005 1.012 1.011

B & L Smoke .3525 .3802 .3963 .4664 .0193 .1854 No 4 1.003 1.003 1.002 1.002 1.005 1.005

Cool Ray .3518 .3796 .3957 .4659 .0193 .1849 blue/green 1. 001 1.001 1.001 1. 001 1.003 1.002

No glass filter .3513 .3791 .3953 .4653 .0192 .1845

Poloroid Neutral .3506 .3783 .3945 .4649 .0191 .1339 .9979 .9981 .9982 .9888 .9964 .9969

I I-' (j\ I

APPENDIX C

�,_............._......_.,............- -....,.__,-- ..-....__,___ ...... ___ \ = �,

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�oo - �' •20 oo aoo �·-o aeo 420 uo 100 No no eio .. o 990 WAV!\.U'tGllt fN Mtt.U�N$ 'r

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16 . ,I

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29

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