S4 Ellipsoidal lamp size

According to the wiki:

The only physical differences between the S4 750 and S4 575 are: the cable, an extra hole in the light baffle in the lamp housing assembly which accomodates the 750W lamp key pin, and the paint on the reflector housing. The reflector did not change.

So changing the cap assembly replaces all these components.

Unless the paint on the reflector housing cannot handle the heat?

Perhaps it was an issue, or maybe they just changed over the factory to a particular powder coat at around the same time. All the temperature data for the current line of products is in the wiki too. Unfortunately there is no surface temperature data for the 575W Source Four so it's hard to say if the paint is going to be an issue. I guess it also depends on operating conditions for each fixture.

Perhaps it was an issue, or maybe they just changed over the factory to a particular powder coat at around the same time. All the temperature data for the current line of products is in the wiki too. Unfortunately there is no surface temperature data for the 575W Source Four so it's hard to say if the paint is going to be an issue. I guess it also depends on operating conditions for each fixture.