fig1 shows a parking garage 10 and a light assembly 20 used to provide light for the parking garage 10 . a parking garage 10 ( e . g ., a parking garage attached to a building or a stand alone parking garage ) often includes multiple lighting fixtures that , due to security concerns , often burn 24 hours a day , 7 days a week . since the lights in the parking garage 10 are illuminated for such lengthy time periods , lighting often represents a majority of the parking garage &# 39 ; s utility bill . as such , retrofitting the parking garage 10 with higher efficiency lighting fixtures can result in substantial savings for the parking garage 10 . in addition to the extended use of the lighting in a parking garage setting , lighting used in a parking garage 10 must be able to withstand varying weather conditions . for example , the lighting must perform in wide range of ambient temperatures including temperatures below zero degrees fahrenheit and as high as 120 degrees fahrenheit . while traditional fluorescent light sources have been significantly affected by such extreme temperatures , recent advances in fluorescent lamp and ballast technology have allowed fluorescent lamps to strike and run at below zero degrees fahrenheit with high efficacy . as such , retrofitting a parking garage 10 with higher efficiency lighting fixtures that can withstand the temperature ranges and extended periods of use can result in substantial savings for the parking garage . fig2 shows an exploded view of the lighting assembly 20 for retrofitting an existing light fixture with a higher efficiency assembly including two pl fluorescent lamps , a light reflector and a backing plate . not shown , but included in the system is a new ballast which powers these new pl lamps . for example , this lighting assembly 20 can mount into an existing high intensity discharge ( hid ) based low ceiling height fixture ( e . g ., low bay ) the lighting assembly 20 can be used to retrofit a variety of fixture designs with this including low bay fixtures from manufacturers such as hubbell kim which has a place of business at 701 millennium blvd , greenville , s . c . 29607 , cooper lighting which has a place of business at 1121 highway 74 south , peachtree city , ga . 30269 , and genlyte group llc which has a place of business at 10350 ormsby park place suite 601 , louisville , ky . 40223 . in so doing , this common assembly design substantially reduces the operating and maintenance costs while preserving the required illumination levels of these fixtures . the lighting assembly 20 includes a backing plate 52 , lamp holders 42 and 44 , lamps 34 and 38 , a ballast , and a light reflector 32 . the backing plate 52 mounts inside an existing light fixture housing to allow retrofitting of the existing light fixture . the lamps 34 and 38 are connected to the backing plate 52 by lamp sockets 36 and 40 which are attached to the lamp holders 42 and 44 connected to the backing plate 52 . openings 28 and 30 in the light reflector 32 allow the reflector to fit over the lamp holders 42 and 44 . the light reflector 32 is formed of a highly reflective material and increases the amount of light directed to the target from the pl lamp . the light reflector 32 is secured to the backing plate 52 by screws or other attachment devices . after installation of the light reflector 32 , lamps 34 and 38 are inserted into the lamp sockets 36 and 40 so that a portion of the light emitted by the lamps 34 and 38 is reflected out of the light assembly 20 by the light reflector 32 . fig3 shows an exemplary backing plate 52 . the exterior shape ( e . g ., the size and shape ) of the backing plate 52 can vary to allow the backing plate 52 to fit into an existing fixture &# 39 ; s base housing which itself is attached to an electrical connection and roof bracket . the backing plate 52 provides a standardized interior shape that accommodates a common light reflector design so that the same light reflector 32 can be used with multiple backing plates 52 having different exterior shapes . for example , the size and placement of the lamp holders 42 and 44 in the interior portion of the backing plate 52 is the same for backing plates of different sizes and shapes . the backing plate 52 has an integrated design for lamp holder brackets 42 and 44 which protrude from the interior portion of the backing plate 52 . the lamp holder brackets 42 and 44 allow the backing plate and arms to be manufactured from a single piece of metal . during installation the lamp holder arms are bent to about a ninety degree angle with respect to the surface of the backing plate 52 . the lamp holder brackets 42 and 44 include openings 43 and 45 through which a high voltage insulation tube can be fed . lamp sockets 36 and 40 can be attached to the lamp holder brackets 42 and 44 and socket leads from the lamp sockets 36 and 40 can be inserted into the high voltage insulation tube prior to feeding the high voltage insulation tube through the openings 43 and 45 . the backing plate 52 also includes multiple air holes 54 that provide ventilation into the lighting assembly 20 . the air holes 54 are openings stamped into the backing plate 52 . the air holes 52 allow improved thermal efficiency for the ballast , and reduce the high temperature characteristics of the cavity . in the embodiment shown in fig3 , the air holes 52 are small circular openings arranged in a grid - like fashion . however , other arrangements and shapes of the air holes 54 are possible . the backing plate 52 also includes multiple clips 48 , 49 , 50 and 51 for attaching an electrical insulation material such as fish paper 46 to the backing plate 52 . the fish paper 46 provides a cover between the lamp area and the interior of the fixture housing ( e . g ., for ul approval ). in some embodiments , the backing plate 52 is produced from a single piece of metal . for example , the backing plate 52 can be stamped from non coated aluminum and the lamp arms 42 and 44 are bent to be perpendicular to the backing plate surface . lamp sockets 36 and 40 are mounted to the interior lamp arms 42 and 44 on the backing plate 52 . a variety of exterior sizing and shapes for the backing plate 52 are defined for different commercially available fixtures . fig4 and 5 show two exemplary sizes of the backing plate 52 . more particularly , fig4 shows a large backing plate that would be suitable for use with , for example , cooper fixtures or other similarly sized fixtures . fig5 shows a small backing plate that would be suitable for use with , for example , hubbell kim pgl fixtures or other similarly sized fixtures . in general , different backing plates can be similar in shape such that the different sizes of backing plates can be used with the various external dimensions inside different fixture housings . fig6 and 7 show a cross - sectional side view and a side view of the light reflector 32 , respectively . the light reflector 32 optimizes light output generated from two cross mounted opposed pl lamps . the light reflector 32 has conical shape which provides optimized reflection and light dispersion from a variety of different wattage pl &# 39 ; s , while accounting for their similar form factors and range of lengths . the slope of the light reflector is greater near the center 33 of the reflector and decreases with increased distance from the center 33 . the slope decreases with increased distance from the center 33 in order to maximize the fixture efficiency as well as improved dispersion of light , a key element in low bay fixtures . the shape of reflector 32 allows the reflector to perform in a variety of fixtures and especially allowing high angle light to pass thru the clear windows in some models for lighting the ceiling . in addition , the shape of reflector 32 allows for use with a variety of lamp wattages and sizes . as shown in fig8 , the light reflector 32 includes an outer rim 25 that is flat and does not slope . the flat rim 25 allows for easier installation and attachment of the reflector 32 to the backing plate 52 . the reflector 32 includes screw holes 24 a , 24 b , and 24 c ( fig9 shows an expanded view of a screw hole in the reflector 32 ) to secure the reflector 32 to the backing plate 52 after the backing plate 52 is inserted into the fixture . the light reflector 32 also includes rectangular holes 28 and 30 which allow attachment of the reflector 32 after the backing plate 52 has been secured to the fixture housing potentially reducing installation time for the light assembly 20 . the light reflector 32 can be manufactured from a number of metal materials . one exemplary material for manufacture of the reflector 32 is a highly reflective alanod mo 4 aluminum material . for example , the reflector 32 can be fabricated from alanod coated aluminum sheet through a spun metal process . as described above , the lighting assembly 20 retrofits into existing hid based fixture housings , converting the existing fixture into a more energy - efficient fluorescent pl - based design . the assembly design is cost efficient in that it ( i ) leverages a common light reflector design which increases the lamp ( s ) performance ( ii ) can be installed very quickly utilizing a universal backing plate which accommodates multiple fixture designs and ( iii ) integrates the lamp holders into the backing plate which allows for a lower cost of manufacturing . fig1 shows a process 100 for installing the lighting assembly 20 . process 100 includes two main portions ; first a portion of the old light fixture is removed including the lamp and subsequently the new light assembly is installed in the existing fixture housing . more particularly , the process for installing the new lighting assembly includes removing the current fixture diffuser lens ( 102 ). the process also includes removing the existing hid lamp ( 104 ), removing the hid lamp socket , and optionally the base plate and existing reflector ( 106 ). the process also includes potentially removing the existing ballast , starter , and restrike lamp ( 108 ). after these portions of the existing lamp structure have been removed , the lighting assembly 20 is used to install a new , more efficient light . the process for installing the lighting assembly 20 includes attaching the new ballast to the fixture housing ( 110 ) and attaching the incoming electrical wiring to the new ballast ( 112 ). the process also includes bending the lampholder brackets to approximately a 90 degree angle from the baseplate ( 114 ). after the lampholder brackets are bent into place , the process includes attaching pre - wiring in the lampholders to the new ballast ( 116 ) and attaching the baseplate to the fixture assembly ( 118 ). the process for installing the lighting assembly 20 also includes inserting fish paper into the pre - designed slot area ( 120 ). the process for installing the lighting assembly 20 also includes attaching the light reflector over the baseplate and lampholder assembly ( 122 ) and inserting two pl - lamps into lampholders ( 124 ). after the lamps have been inserted , the process includes re - attaching the existing fixture diffuser lens ( 126 ). fig1 shows a process 130 for attaching the lamp to the lamp holder . process 130 includes sliding plastic sleeves over socket arms ( 132 ) and inserting wires into the sockets ( 134 ). the attachment process 130 also includes feeding the wires through the socket bracket holes and sleeves ( 136 ) and attaching wire ties to each side around wires and sleeve ( 138 ). after the wires have been fed through the brackets and the wire ties attached , the process includes attaching the socket to the socket bracket ( 140 ) and packing the assembly ( 142 ). it is to be understood that the foregoing description is intended to illustrate and not to limit the scope of the invention , which is defined by the scope of the appended claims . other embodiments are within the scope of the following claims . for example , while the lighting assembly 20 has been described for retrofitting the hid based lighting fixtures in a parking garage 10 , the lighting assembly 20 can also be used to retrofit other hid based lighting fixtures typically used in warehouse , industrial or commercial applications . other embodiments can include a specifically designed pl based retrofit assembly that accommodates a variety of hid based outdoor lighting fixtures such as box shaped street lights from manufacturers such as hubbell , wall washer fixtures , billboard lighting fixtures from various manufacturers and cobra head street light fixtures . the assemblies for these fixtures would include of a different shaped light reflector which was parabolic instead of conical and has a similar integrated backing plate with lamp arms . the design would accommodate multiple fixture sizes and multiple wattage pl lamps depending on the light level performance necessary for the application . for example , fig1 a and 12b show an exemplary use of a retrofit assembly with a shoebox style light fixture 150 . the shoebox style light fixture 150 includes a housing 151 that is substantially box shaped ( e . g ., rectangular ). a retrofit light assembly can be used for retrofitting an existing light fixture with a higher efficiency assembly including two pl lamps 154 , a light reflector 156 and a backing plate 160 . the exterior shape ( e . g ., the size and shape ) of the backing plate 160 can vary to allow the backing plate 160 to fit into the existing base housing 151 of the shoebox style light fixture 150 . in addition , the light reflector 156 can be shaped to optimize light output from the shoebox style light fixture 150 . the retrofit light assembly for the shoebox style light fixture would be suitable for use with , for example , genlyte fixtures , lithonia fixtures , hubbell fixtures or other similarly sized fixtures . in another example fig1 a and 13b show an exemplary use of a retrofit assembly with a sign - light style light fixture 170 . the sign - light style light fixture 170 includes a housing 182 and a cover 174 located on top of the housing 182 . the housing 182 is wider at a back end of the housing than at a front end of the housing ( e . g ., as indicated by heights 178 and 180 respectively ) such that the cover 174 is sloped with respect to a bottom surface 179 of the housing 182 . a retrofit light assembly can be used for retrofitting an existing sign light fixture with a higher efficiency assembly including two pl lamps 172 , a light reflector 176 and a backing plate 184 . the exterior shape ( e . g ., the size and shape ) of the backing plate 184 can vary to allow the backing plate 184 to fit into the existing housing 182 of the sign - light style light fixture 170 . in addition , the light reflector 176 can be shaped to optimize light output from the sign - light style light fixture 170 . the retrofit light assembly for the sign - light style light fixture would be suitable for use with , for example , cooper fixtures , hubbell fixtures , lithonia fixtures or other similarly sized fixtures . in another example , fig1 shows an exemplary backing plate 200 . the exterior shape ( e . g ., the size and shape ) of the backing plate 200 can vary to allow the backing plate 200 to fit into an existing fixture &# 39 ; s base housing . the backing plate 200 can be attached to the existing fixture &# 39 ; s base housing by inserting screws into apertures 206 a , 206 b , and / or 206 c . additionally or alternatively , the backing plate 200 includes bendable tabs 208 a , 208 b , and 208 c which can be used to attach the backing plate 200 to the existing fixture &# 39 ; s base housing . the tabs 208 a , 208 b , and 208 c can be bent out from the surface of the backing plate 200 to allow mounting of the backing plate 200 to the sides of a reflector or external fixture housing . the backing plate 200 also includes lamp holders 202 and 204 which protrude from the interior portion of the backing plate 200 and multiple air holes 210 that provide ventilation into the lighting assembly . the backing plate 52 also includes multiple clips 212 , 214 , 216 , and 218 for attaching an electrical insulation material such as fish paper 46 to the backing plate 52 .