Barco guys, how much are you defocusing blue?

Hi Casey,

I'm afraid there is no right answer to this question. It should be defocus to whatever value gives the right grayscale tracking on midrange (30-70 IRE). Because is dependent on so many things, like ambient light, screen size, resolution used, tube condition etc. there is no way someone could say " well, a blue defocus at this value gives the best results ".
I remember folks having the blue defocused at 0 and others letting it at 57 in order to obtain a linear grayscale. We need to defocus in order to get more light output (the sharper the focus, the darker the image) and luckily, the human eye is pretty unable to focus on blue. So don't worry if the blue test pattern looks terrible out of focus, during film watching you won't notice a damn thing.
From my experience, if there is no possibility to do a grayscale calibration with a proper spectrometer and the blue tube is pretty fresh, the defocus value should be somewhere between 35-45. Mine is at 40 and is not professional calibrated.
Give it a try and compare each time with, for example, watching at Ice Age on a scene with a lot of snow. If the snow goes slightly to the reddish side, you need more blue defocus.
Right, don't forget to touch the optical blue focus as well if you change the electronic focus.