The ERS fixture requires a bench focus / lamp alignment / tuning.
Well, we wouldn't have to do that (and in fact I don't recall hearing "Source Four Leko") until ETC came out with the Source Four PAR. "Source Four" is vague, and "Source Four E. R. S." is too many syllables.
I've always called it a Back Focus, from my days in video.
An I wrong or is there two names for the same thing?
Guilty. Being in Wisconsin and relatively young, I have only had to work with an ERS that wasn't a Source 4 on about 5 occasions. I currently only have etc ERSs, pars, parnels, and fresnels. So although my students are taught the correct terms in the class, the ones that work with me know the fixtures as Source 4s, pars, work lights, cyc lights and fresnels.