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Discussion Starter · #1 ·
I have a Sony D-50 with a Denon D 2800 in progressive mode and want to gray-scale calibrate the system.

I bought an VA-1 colorimeter from AV-Science to do the job.

The contrast from the projector is set to 77 and the brightness to 37 (set with AVIA).

The VA-1 read 19.6 fL in the 100IRE windows pattern.

I think thats too much for the Sony. If I reduce the contrast until the VA-1 reads 12.8 fL the picture is too dim. I think the VA-1 shows the wrong Y values.

What can I do to calc the correct values from the VA-1 readings.


Should I use the 20 or 30 IRE window pattern for the bias and should I use the 80 or 100 IRE pattern for the gain calibration.


The Sony manual tells not to touch the blue gain.

Should I use the blue and red gain or the blue and green gain.


Do I need the G2 control?


An excel file with the VA-1 readings is attached.


Many questions ,any hints ?

 

sony_gamma.zip 6.64453125k . file
 

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Hello Beckma


Start with 30 and 80 IRE and when your ready measure it when it's not flat try 40 and 70 IRE

Try to use the red and bleu controls and take green as a reference

Use the window patterns on video essentials avia is way of


Good Luck

Rob
 

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Beckma,


I assume you have the color probe set up to be looking back at the projector?


19fL may not necessarily be too high, it depends on how close the probe is to the projector (the smaller the screen size, the closer the probe is to the projector, the higher the Y reading). Set the contrast so that there is no blooming or defocussing on the peak light outputs.


In order to get a flatter gray scale through the mid and upper level grays, yoou will have to defocus the blue tube (electrical focus). Put up a 100 IRE window, measure the color temp, and rock the blue focus control into and out of focus, and you'll see what I mean. The correct direction of defocus should be clockwise from best focus.


Chuck
 

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Are you taking a reading with the probe pointed at the projector or at the screen? Which calibration file are you using? I don't believe the normal cal files are going to give you a true ft lambert reading. I would run the projector at the Brightness and Contrast settings you arrived at with Avia, they are very close to the ones I normally use with the projector (I just calibrated one a few days ago). If you really want to know ft lamberts, you have to take a reflected reading and you have to have a cal file that has been set up for this.


Wm
 

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Discussion Starter · #5 ·
wm,

I am taking a reading with the probe pointed at the projector and use the crt non contact mesurement with the prj_65 cal file. I use a 78'' wide 16:9 screen.


Did you use at your D-50 calibration the VA-1 or the sony colorimeter which stucks direkt to the 3 crts?

Did you defocus the blue gun?

Which window pattern in AVIA do you use and do you use the red and green or the red und blue gain control?


many thanks


Markus
 

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Markus,


I use a CA-1 colorimeter (same thing as the VA-1); I also use a McMahan Lightspex as a reference (and to take accurate foot lambert readings).


A true foot lamberts reading can only be taken by reading the light reflected from the screen, and the probe has to be calibrated for this. I'm not sure what the cal file you are using was calibrated for. I know the software says "foot lamberts" but the actual value depends on how the cal file was built.


Yes, I defocus blue. It's very important to determine which side of defocus produces an even defocus. When you adjust the focus pot, one side of defocus will produce the "flare", a bright line inside a softer wider line, and the other side will produce a uniformly defocussed line. This is the side you want to be on. I adjust until the line just starts to bloom, add more only if I have to to get d65.


I use 100 IRE Window to set the Gain and 20 IRE window to set Bias. The 80 IRE window pattern is a good check to make sure you aren't overdriving the blue crt and running out of blue.


Usually blue Gain is maxed out or close to it, this is pretty normal for most Sony projectors.


For final calibration you may want to point the probe at the screen. If it's a Stewart this is probably not necessary, as just about every one I've measured has been so close to perfect white that it doesn't matter.


Hope this helps.


William
 

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Discussion Starter · #8 ·
wm,

do you set the VA-1 measurement relative to green and use the blue and red gain controls of the sony or do you set the VA-1 measurement relative to blue and use the red and green gain controls.

I ask because the sony service manual says not to touch the blue gain control.


many thanks


Markus
 
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