[takev]

Hello,


I have a light controled room a Sony 1270 and a screen width of 1.5m and a throw distance of 2m.


I have now sharply e-focused the blue tube. And I have redone my white and greyscale tracking, which is linear, even for the blue tube.


Will my phosphor wear faster, now I have focused my blue? As I see it, the blue tube is still producing the same amount of light, but I'm not an expert of phosphor usage. (I guess the catode will wear a bit faster as more electrons are pulled out)

 

[Tinman]

Generally the blue is defocused just slightly to aid in white uniformity. You can see this effect on an all white screen. For instance, the NEC projectors have a switch in them that AFTER you set everything up properly, when flipped on will defocus the blue by a preset amount. I did notice that the overall white level and uniformity were indeed better with the tube just a bit defocused. Also, we cannot see blue as well as other colors, so the slight change is unnoticable to the eye. Various other reasons include the fact that the blue is the dimmest color, and thus won't have to drive as hard when purposely blurred to use a bit more phosphor. Try it for yourself. Not sure if there is any one absolute answer, but I have presented the most common one.

Hope this helps.


Marc

 

[takev]

I know it helps to defocus to get more light from the blue tube.


But I don't drive my projector hard at all, so the blue tube can keep up completly focused.


However with the extra electrons hitting the fosfor, will the tube surface wear faster, focused then defocused?

 

[Tinman]

Possibly. It's your call. I'll stick to what's in the manuals.


Marc

 

[Tom Morrow]

Whether focussing the blue gun accelerates phosphor burn is an interesting question. Clearly you are focussing the energy of the beam in a smaller area, so at any given time more electrons are heading towards the phosphor. But focussed or defocussed, the energy of the beam will be divided over the whole screen, since it scans the whole raster every 1/60th of a second. I suppose it boils down to how quickly heat dissipates from the phosphor. If it dissipates slowly, then focussing and defocussing are likely to be roughly equivalent, since the whole raster is being scanned.

But if the heat dissipates quickly (relative to the time it takes to scan a line) then the focussing would make things worse.


-Tom

 

[takev]

Tom, yip, this is what I mean.

But I guess you can only know by testing it, and

probably nobody is doing this, I've tried to find papers about this on the Internet, but I couldn't find anything.