"There are several options to retrofit my ETC Source 4 incandescent fixture to LED. How do I pick the option with the most lumens?"
There are three items that go into the discussion of the ETC S4WRD II LED Lamp Retrofit Kits:
1) Amount of Lighting Output, as measured by Lumens
2) Color Rendering Index (CRI), which is how true to color are objects that being lit by the LED.
3) Color Temperature, what is the color of the light as it is produced. In this case there are two options: 3200K (warm) and 5900K (cool).
There are three variations of the ETC S4WRD II LED Lamp:
1) ETC S4WRD II LED Lamp 3200K, 80 CRI Rating (S4WRDT120)-Source 4WRD II Retrofit Kit, which has the most light output at 11,430 Lumens. ETC S4WRDT120 Source 4WRD II - Retrofit Kit 120v - GoKnight
This unit is using the "3200K Color Temperature", which is very close to a standard incandescent lamp, but the CRI (Color Rendering Index) is the lowest at just 80 CRI. This means that colors of items that you will light with this LED will have an 80% match to their true color.
So, this retrofit will be bright (high lumens), with a warm color temperature (3200 Kelvins) and will provide a very good representation of the color of the objects it is lighting (80 CRI).
2) ETC S4WRD II LED Lamp 3200K, 90+ CRI Rating (S4WRDTG120)-Source 4WRD II Gallery Retrofit Kit, which has the least light output at 9,716 Lumens. ETC S4WRDT120 Source 4WRD II - Retrofit Kit 120v - GoKnight
This second unit is using the "3200K Color Temperature", which is very close to a standard incandescent lamp AND the CRI (Color Rendering Index) is very good at 90+ CRI. This means that colors of items that you will light with this LED will have a 90+% match to their true color.
That is why this model is called the "Gallery" Retrofit Kit. This is used in areas where the user wants the objects that are being lit to have a very true color rendering, such as a gallery, museum, art, or anything that wants the purest colors possible.
This unit stays at the 3200K Color Temperature, which is that warm, orange/yellow color that you think of when an incandescent lamp is dimmed.
So, this retrofit will be a little less bright (average lumens), with a warm color temperature (3200 Kelvins) and will provide an excellent representation of the color of the objects it is lighting (90 CRI).
3) ETC S4WRD II LED Lamp 5900K, 90+ CRI Rating (S4WRDDG120)-Source 4WRD II Daylight Gallery Retrofit Kit, which has the middle light output at 10,333 Lumens. ETC S4WRDDG120 Source 4WRD II Daylight Gallery Retrofit Kit - GoKnight
This third unit is using the "5900K Color Temperature", which is very close to daylight and has more blueish white in the color temperature AND the CRI (Color Rendering Index) is very good at 90+ CRI. This means that colors of items that you will light with this LED will have a 90+% match to their true color.
That is why this model is called the "Daylight Gallery" Retrofit Kit. This is used in areas where the user wants the objects that are being lit to have a very true color rendering, such as a gallery, museum, art, or anything that wants the purest colors possible.
This unit is different with a 5900K Color Temperature, which is that cooler, blueish-white color that you think of with a cool fluorescent lamp tube.
So, this retrofit will be nice and bright (above average lumens), with a cool, "blue-white" color temperature (5900 Kelvins) and will provide an excellent representation of the color of the objects it is lighting (90 CRI).
SUMMARY
In regards to the light output, option 1 will provide you with the most light output, but will provide you with the least capability in Color Rendering Index. The second option provides you with that warm color temperature and Color Rendering Index, but has slightly lower light output. The third option changes color to 5900K Color Temperature (more blue/white light output) and the Color Rendering Index is very good, as well. The light output is also good, but not this unit does not have quite as many lumens as option one.
There is a lot to consider when choosing the correct LED retrofit for your lighting. If you would like assistance, we are happy to help! Just call our friendly "techsperts" toll-free at 866-457-5937.