[htmike]

I've been re-adjusting my sony 1271 and I cant get the blue gun completely focused. Now I know that the blue is not supposed to be focused but I would like to focus the gun and the de-focus as needed. I am using the 2-4 pole and the g2 adjustment.

Any thoughts?

 

[Energeezer]

In my experience my EYES do not focus on blue as well as green and red.

 

[kal]

I've also noticed that our eyes aren't at all sensitive to a defocussed blue (within reason of course). You can defocus pretty far before you notice anything.


Test: Put up a test pattern of some sort and play with the electronic focus for blue and green (one at a time). Green focus problems are very noticeable, blue is not.


Some blue focus is desirable for better grey scale tracking as well. (How much is ideal, only the guy with the colorimeter can tell you...)


Kal

 

[Mikedd]

On my Marquee, I have almost perfect D6500 tracking from 30IRE to 100IRE with the blue tightly focused. De focus of blue may be necessary as the light output diminishes. Your Sony is most likely electrnically de focussed by about 12% fo optimal light output. I watch in a completely darkened environment and run my projector at conservative values.


Mike

 

[FoLLgoTT]

The human eye has far less receptors for blue than for red and green (most for green). So we cannot resolve high resolutions in the blue part of pictures. We can see green best. It depends of green if pictures look sharp or not, so it is important that the green tube is focused as good as one can get it.

 

[Guy Kuo]

Yes, you can focus the blue gun, but a pair of binoculars is almost mandatory. On a grosser scale you can "see" when the blue beam is maximally focused by noting how much blue light is coming from the screen. As you adjust blue beam focus, you'll notice that the blue gun output drops just as maximal bean focus is reached.

 

[Tinman]

Wow, Guy.... Bean focus? Another new technique, I guess.


Anyway, Guy is absolutely correct. To focus blue, I simply look at a blue crosshatch pattern and change focus until it suddenly is at it's dimmenst. That's optimal focus. On the NEC, then flip the De-focus switch to obtain the best white balance. On some, this does not work well, so I use a colorimeter anyway.


Marc

 

[Guy Kuo]

BTW, the magnitude of drop in blue light output also illustrates how large a drop in max white intenstiy you'll be able to obtain (and keep grayscale flat) if you fully focus the blue gun.

 

[sunghoon]

htmike: Are you talking about the dot or beam sizes? I was trying achieve the very same thing with my own vph1271q. I replaced a new set of pix tubes. I had no trouble with the red and green tubes. I could tighten red and green beam well by manupulating those magnetic rings. Blue tube was a totally different story. Blue dots were about twice larger than others. I could see blue edges around bright white images. I spent many weeks trying to better the blue beam with the manetic rings. I finally got the blue dots small enough that I don't see any blue on whites. Blue dots are still lot bigger than others.

 

[deronmoped]

Does this make sense. Why bother to get sharp focus on the blue, if you are going to defocus it in the end.


Get it close and leave it?


Deron.

 

[mark haflich]

Remember for the same beam current as the red and green, the blue puts out more light at low IRE and less at high IRE. Defocusing about 25 percent is what we did in the old days for machines that didn't have gamma correction on the blue. On machines that have gamma correction such as the later Marquees and Ampros, defocusing is not necessary, so make it sharp. Defocus if you do not have a machine with gamma correction. Many calibrators make a point of obtaining sharp focus on the blue for all machines amd then do not obtain a close to level line across all IREs. ISF doesn't train you to be a competent calibrator. Since your eyes don't need the blue to sharp, if your machine requires a defocused blue to obtain the best 6500K gray scale, defocus and don't worry.

 

[Phil Smith]

I calibrated my G70 once to defeat defocus and I lost a lot of light output. I quickly switched it back to normal. Also, the better I get at focusing, the dimmer my projector becomes. Same with resolution. The higher it is, the dimmer it is.