(If you don't want to read an overview of the advantages of the DL50 skip to the bottom for the eBay seller and the price).
The Philips DL50 is a ďpremiumĒ D2S bulb with longer life, better performance, and higher maximum wattage compared to standard D2S bulbs (Philips 85122, Osram, GE). To see how it compares to the GE bulb at 50W look at the pictures by Mr. Ted Bear in the barn burner thread. It puts out more lumens, has more throw, lights up a larger area, has a more uniform hotspot, and has a more neutral colour than the GE bulb (GE bulb has a slight pinkish tint). XeVision says it canít be used at 35W, so it can only be used as an upgrade for 50W systems such as the XeVision 50W, and it is the only bulb that can be driven at 75W as with the XeVision barn burner.
In the barn burner thread mtbkndad said: ďOn another note there was more of a difference between the three configurations in the park then the pictures can show. The difference was pretty evenly stepped from a 50Xe/GE to 50Xe/DL50 to 75Xe/DL50. All three were quite bright so the difference is really between three different levels of enough light to see across that part of the park.Ē
There is a comparison at http://nuconverter.de/spectraldatapage.html that says: ďComparison of a DL50 with an overpowered D2S from GE: The GE bulb has less blue spectral intensive lines than the DL50. The typical xenon look of the GE is lost and there's less light output as well. As a conclusion a 50W Xenon system requires a 50W bulb.Ē
While everyone in the barn burner thread agrees that the DL50 is better than the GE bulb, most donít think that itís worth 3x the price of the GE bulb, and Iím inclined to agree. XeVision charges $85 for the GE bulb which puts the DL50 at around the $250 mark.
On eBay the DL50 is available from the seller ďbeamer-onlineĒ here for only $99! Itís not exactly cheap, but itís only 17% more than the GE bulb, which is well worth it in my opinion. I emailed the seller and he said that he has hundreds of them and they are all new and unused. For 10 or more the price is only $85, or the same price as the GE bulb! So if someone wants to do a group buy for these we can all get the DL50s for the same price as the GE bulb! There is no point in running the group buy myself because I live in Australia.
The seller also mentions a 70W ballast, but itís 80 Ė 260VAC so it's useless for portable spotlights, although it could be used for home lighting if anyone's interested.