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Recent Trends in Design of Lightning for Sports Broadcasting Manish Shah
Department of Electrical Engineering M. Tech Scholar VITS Indore [email protected]
Department of Electrical Engineering Asst. Prof. VITS Indore [email protected]
Abstract -Old and new generation both are crazy to watch sports of their interest as new generation of athlete has been establishing new land marks in their performance and this become inventible to watch live events. High definition colour television (HDTV) technology created a new view to watch these events and lightning arrangement, it’s planning and designs are crucial task before broadcasting companies. Keywords- Aspect Ratio, Flickering, Glare Effect, High DefinitionTtelevision, Illuminance, , Polar Curve
I. INTRODUCTION Sports events are not merely a passing the extra time or maintain physical fitness now a days instead acquired highly professional makeover, lot of peoples are engaged in playing sports professionally & leading companies of world sponsors the entire sport events. Other few companies are engaged in broadcast these events. Peoples are now keen interested to watch these events but only few thousand may actually watch live in stadium, others watch it on various television channels. This ration is approximately 1:2000 With the advancement of high definition television during the Barcelona Olympic 1992 the watching of these events has made a exciting job all over the world as images & videos are so closer to real take. Broadcasting engineers are progressive to provide viewer immersive high definition coverage of sports events. The higher resolution& aspect ration of 16:9 together have surged the demand for exotic coverage of sports events. HDTV cameras capture & shoot high quality images & videos. These images are sharp & highly detailed and HDTV broadcasting has been making revolution through frequent use of close ups of Athlete & celebrities sitting in stadium & slow motion shoots of special portion of event. It is expected that up to London Olympic 2012 leading broadcasting companies of world will upgrade their TV studio & live coverage system to suit HDTV.
II. PLANNING FOR LIGHTNING SYSTEM The below written parameters should readdressing and take care for planning of broadcasting: a.
The CIE recommended three lightning levels characterized by dimensions of the objectives and speed of action occurring during camera shot. This relates sports category to service illuminance. The recommended maintained illuminance of CIE 169:2005 is related to service illuminance as fallowing:
(1) 0.8* E service initial (2) E 0.8* E 0.64 E maintained service initial *maintenance factor The relation between service illuminance and maintained illuminance is explaining below with figure 1: E
Figure1-Service Illuminance & Maintained Illuminance
When focus has to do on moving subject with precision from a certain distance especially for close up, framing required more depth of camera field. The slow and replay shot require capturing more frames per second. Modern HDTV cameras are extremely sensitive even work in low light too but strive for more picture frames and higher depth of field demands higher illuminance. The
requirement of more illuminance also strengthened distinction between main camera and moving camera. Therefore the lightning level should increase to achieve desired clarity and exposure. This increase in lightning level depends upon speed of game. The existing broadcast of 720p is going to replace by 1080p with exiting grain texture and more frames. b. Colour Temperature of Lightning While installing indoor or outdoor sports lights the colour temperature of artificial light would be kept between 4000K and 6000K. The apparent colour temperature changes within a scene should be minimized due to reduction in daylight and require contribution of artificial lightning. The colour temperature of lamp should not deviate from average value of 50K. This is because unlike human eye cameras can adopt to one colour temperature. c. Colour Rendering of Lightning Source One international agency recommended different minimum required colour rendering for various sports activities such as physical training, match practice and professional competition. Now reference suggests minimum colour rendering Ra of 90 for professional competition however up to previous competition like FIFA 2007 still continue Ra grater than 65 and other sports federation recommended Ra 80 and some of 90 for professional competition. The colour rendering index Ra should be more than 90 for conventional TV (CTV) and HDTV for viewing sports events with distortion free colour reproduction. The lamps with Ra less than 80 are lacking in the red colour , result is not faithful capturing of red, brown and orange by camera, such distortion in generally not acceptable to advertisers and sponsors as they rely on colour fidelity to show their brand. The table 1 gives a general view to colour output of various lamps. TABLE I - COLOUR OUTPUT OF VARIOUS LAMPS S No. Lamp specification Color 1
Hg under low pressure
Hg under high pressure
d. Flicker Effect When high discharge illumination lamps operated on AC circuit, give a considerable flicker, results
stroboscopic effect on fast moving objects. The above effect is viewable during slow motion replays. It is because each frame captures the artificial light at different points in the sine wave causes a flicker if frame rate does not synchronize with lightning frequency. The total electrical load of sports arena should be equally divided in to three phase balance system for elimination of above effect. Therefore other aiming pattern should consider electrical load balancing for each switching option. Rendering software has to be deployed so adjust the aiming angles for sports lightning to interlace to eliminate shadows for broadcasting and give electrical phase balancing to minimize flicker. The above written solution will merely minimize the flicker and not completely eliminate it. e. Glare Minimization The rating of glare depends upon luminous intensity distribution, aiming of luminaries, their number, arrangement, mounting height and brightness of illuminated area. The present restriction for maximum glare at different points of arena should also include overall glare so the player should fill comfortable at every point during movement otherwise it will seriously affect the performance of player. The lamp should always deploy with opaque glass or with similar material to minimize glare. f. Sky Glow The CIE and other international agencies of sports recommended controlling spill light. It is fill that these recommendations may be made simpler and more stringent. For initially luminaries with different aiming angles the portion of total flux of luminaries directly emitted at and above horizontal is
DLOR ULOR (3) ULOR Where ULOR=cumulative upward light output ratio of all luminaries of lightning ULR
DLOR=Cumulative down ward light output ratio of all luminaries of light. The above written method does not include photometric properties of surface for, for this an alternative method is suggested:
upnist Sky glow la
la = total lamp flux installed
upnist = upward lumen flux of installation, upward lumen flux of installation has two components ( i ) Direct flux to sky. ( ii ) Reflected flux to sky. This method require computation of total upward lumen flux and for computation photometry software are available, that can generate ULOR for different angle of tilt of a luminaries for computing reflect flux to sky, estimate of downward light ratio of installation.
b. PolarCurve To determine illumination of a point through E I cos / r 2 , find luminous intensity of source of light in that direction through appropriate meter as due to various practical reasons luminous intensity is not same in all direction. If luminous intensity is measured in horizontal plane passing through the source of light and plotted for various angles, we get horizontal polar curve as shown in figure-4.
III. DESIGN OF LIGHTNING SYSTEM Design of lightning system for sports is depends upon the following parameters: a . Laws of Illumination I) Inverse square law: It says that illumination at a point is inversely proportional to square of its distance from the point source and directly proportional to luminous intensity. Let I =luminous intensity lumens/steradian ω= solid angle as shown in figure-2
Figure-4 Horizontal polar curve
Vertical polar curve gives the relation of candle power in vertical plane passing through the lamp at various angles. Figures 5 show the polar curves of lamp.
Figure2-Inverse Square Law
E r 2 1 2 (5) 2 E 2 r1 Where E1= Illumination at surface of radius r1 E2= Illumination at surface of radius r2 II ) Cosine law: The illumination at a point on a surface is proportional to cosine of angle which ray makes with normal to surface at that point. From the figure-3 I cos (6) E r2
Figure-5 Vertical polar curve
c. Lamp Selection and Installation For lamp selection first calculate the total area to be illuminated than find the required level of illumination through data given by particular organizing authority. As one generally used lightning level is estimated from table-2. Figure2- Cosine law
TABLE-2 ILLUMINATION LEVEL FOR SPORT EVENT S. No. 1 2 3 4 5
Race Tennis Cricket Foot ball Hockey
200-250 300-550 250-350 200-300 250-400
Up to end portion of lightning source some overlapping is essential to overcome from darkness shown in HDTV broadcasting. As per lamp efficiency and other parameters of HDTV broadcasting such as colour selection, glare rating, shadow formation CFL & high discharge lamps are preferred over conventional lamps, the table 3 shows out put of various lamps with electrical input: TABLE-3 OUTPUT OF VARIOUS LAMPS WITH ELECTRICAL INPUT S. No. 1 2 3 4 5 6
Fluorescent lamp Fluorescent lamp Mercury discharge Mercury discharge Sodium discharge Sodium discharge
80W- 5ft. 40W-4ft. 400W
Lumen output 4640 2400 15600
After selection of lamps these have to install on a specific height on steel poles or towers with average height of 16m. For outdoor stadium these combinations have to incline from vertical axis as per requirement. d. Factor AffectingIillumination Illumination is not only depend upon its lumens output of lamp but is multi factor dependent parameter few practical factors are 1) Utilization factor 2) Maintenance and Depreciation factor 3) Waste light factor e. Aspect Ratio The aspect ration play an important role in sports broadcasting as HTDV version requires specific images to display, a minor error is clearly visible during live games. The aspect ratio of an image is the ratio of the width of the image to its height, expressed as two numbers separated by a colon. That is, for an x:y aspect ratio, no matter how big or small the image is, if the width is divided into x units of equal length and the height is measured using this same length unit, the height will be measured to be y units. For
example, consider a group of images, all with an aspect ratio of 16:9. One image is 16 inches wide and 9 inches high. Another image is 16 centimeters wide and 9 centimeters high. A third is 8 yards wide and 4.5 yards high. Aspect ratios are mathematically expressed as x:y (pronounced "x-to-y") and x×y (pronounced "xby-y"), with the latter particularly used for pixel dimensions, such as 640×480. Cinematographic aspect ratios are usually denoted as a (rounded) decimal multiple of width vs unit height, while photographic and videographic aspect ratios are usually defined and denoted by whole number ratios of width to height. In digital images there is a subtle distinction between the Display Aspect Ratio (the image as displayed) and the Storage Aspect Ratio (the ratio of pixel dimensions). The most common aspect ratios used today in the presentation of films in movie theaters are 1.85:1 and 2.39:1. Two common videographic aspect ratios are 4:3 (1.33:1), the universal video format of the 20th century and ; 16:9 (1.77:1), universal for high-definition television and European digital television. Other cinema and video aspect ratios exist, but are used infrequently. As of 2010[update], nominally 21:9 (2.33) aspect TVs have been introduced . In still camera photography, the most common aspect ratios are 4:3, 3:2, and more recently being found in consumer cameras 16:9. Other aspect ratios, such as 5:4, 6:7, and 1:1 With television, DVD and Blu-ray, converting formats of unequal ratios is achieved by either: enlarging the original image (by the same factor in both directions) to fill the receiving format's display area and cutting off any excess picture information (zooming and cropping), by adding horizontal mattes (letterboxing) or vertical mattes (pillarboxing) to retain the original format's aspect ratio, or (for TV and DVD) by stretching (hence distorting) the image to fill the receiving format's ratio, by scaling by different factors in both directions, possibly scaling by a different factor in the center and at the edges f. Electrical Power Supply and Reliability of Broadcasting The broadcasting companies demand reliability of power supply for sports events. To guard against possible momentary dip in supply voltage, the use of expensive hot restrike lamp should deploye on sports arenas. Modern lightning system have PC interfacing and control. A situation based lighting control system is desired. The system should also allow mannual operation in case of emergency such
as operate perticular lamp. Such control will avoid high starting and reignition current by step by step switching. The electrical power supply for sports lighting include following paremeters, equipment and accessories 1)
Calculate the estimated load.
2) Two, three phase 50/60 Hz transformers of equal rating as to eliminate problem related to voltage regulation and relibility. 3) Power supply of 440volt, 3 phase 4) Transformer with control panel equiped with neccesory panel meters. 5) Conductors and conduit for power transfer. 6) Over current and surge relays with circuit brakers 7) Backup UPS through alternators in case of power failure. 8) Appropriate earthing to prevent shocks as lot of spectetor present in arena. CONCLUSION Here the attemp is made to show planning and design paremeters of sports lightning for broadcast & installation with power supply and reliablity. There is still to do a lot in sports lightning sector such as crating more depth with flicker free slow motion coverage. Glare minimization and capturing of more frames for fast moving objects. More investigation are expected for sky glow measurement as residential point to be consider. FUTURE SCOPE HDTV has changed the definition of clear and real video watching but ever-increasing demand for work, made men and women busy even in night too and in this scenario the existing 3G cellular mobile services opened a new door to watch these events even at jogging tracks and during traveling in local trains. Broadcasting companies will have to do a lot for this dimension as the demand for watching sports events on cell phones will increase very rapidly, clarity vis-à-vis various facilities which should support these new mobile phones so the illumination that supports the video with high clarity will major task before task before broadcasting companies.
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