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Calibration Issue

post #1 of 6
Thread Starter 
Hi All,

I've done calibration in the past using the Digital Video Essentials blu-ray and that seemed to work decently. I recently upgraded my projector to the JVC-RS45 and thought I'd splurge a little and get a LumagenMini, Display 3 Pro color meter and Chromapure with auto calibration.

I got everything hooked up and ran the auto calibration, but something doesn't seem to be working right. The before calibration charts of the grayscale and RGB seem to be not too bad. But, after calibration they seem way off. Whereas the CIE94 Chromaticity dE seems to be better after calibration down to 1.8 from 2.4. Being, a novice in the calibration arena, I think that something is wrong, as the resulting picture looks terrible compared to pre-calibration.

Like I said, I'm a bit of a n00b when it comes to this stuff, so I wasn't sure if anyone has any advice on where to begin to correct things.

Thanks!

For reference, here are some pics of the grayscale and RGB report to show what I'm talking about:




post #2 of 6
The auto-cal is a total fail. Doesn't matter what the chromaticity measurements look like, those errors in the grayscale are HUGE and will be highly visible.

Something is clearly wrong with the autocal process. Presumably you can manually adjust grayscale and color to be reasonably accurate?

There can be many reasons the autocal fails... it could be a timing issue where the software doesn't wait long enough for the pattern to change or for the meter reading to complete. When the software doesn't wait long enough for the meter reading to complete, this would likely get worse at darker steps and, on average, your grayscale errors are getting larger at the darker steps (or so it looks from what you can see on the graph anyway).

You could measure how long it takes your meter to make a reading at 20% or 30%, then time the autocal process when it gets to that same step to see if the software is waiting as long as the meter takes to make the reading manually.

The other issue is your pattern source... you didn't say what you were using - presumably because the "before" measurements look pretty good, the software is waiting an appropriate period of time for the pattern to change... when you run autocal again, see if there's a difference in the amount of time the software waits for the pattern while making the "before" measurements vs. the autocal measurement (presuming the software reads all the steps first to get the "before" measurements, then adjusts 1 step at a time to get good results).

You also probably want to see if there's an autocal thread here for your calibration software to see what experience others are having with it. If there isn't such a thread, you could start one.
post #3 of 6
Thread Starter 
Thanks Doug,

I'll have to check the time it takes to perform those operations when I get home. But, it ran a complete calibration in udner 10 mins.

As for the source, I'm using ChromaPure software (via RS-232) connected to the Lumagen to generate the test signals. I'm not sure which one actual does the siginal generation.

I'll have to do some more research and educate myself further to try an understand this stuff better.
post #4 of 6
Thread Starter 
Not to bump my own thread, but it looks like a new version of the ChromaPure software just came out yesterday. I'll try that tonight and see if that helps things.
post #5 of 6
Quote:
Originally Posted by Lamprey View Post

Thanks Doug,

I'll have to check the time it takes to perform those operations when I get home. But, it ran a complete calibration in udner 10 mins.

As for the source, I'm using ChromaPure software (via RS-232) connected to the Lumagen to generate the test signals. I'm not sure which one actual does the siginal generation.

I'll have to do some more research and educate myself further to try an understand this stuff better.

It's the lumagen generating the patterns.
post #6 of 6
Quote:
Originally Posted by Lamprey View Post

Thanks Doug,

I'll have to check the time it takes to perform those operations when I get home. But, it ran a complete calibration in udner 10 mins.

As for the source, I'm using ChromaPure software (via RS-232) connected to the Lumagen to generate the test signals. I'm not sure which one actual does the siginal generation.

I'll have to do some more research and educate myself further to try an understand this stuff better.

In this case, the Lumagen processor is creating the pattern. BUT... the calibration software is sending the command to the Lumagen and that command contains the 'code' required for each pattern. If the software doesn't wait long enough for the Lumagen to produce the next pattern (by telling the meter to start making a reading at the right time), part of the meter's reading could be taken before the right pattern is completely displayed. The calibration software has to send the RIGHT code for the RIGHT pattern also. If the software send the RIGHT code for the correct pattern AND if it waits long enough for the pattern to be fully rendered before telling the meter to start taking the reading, then the problem has to be at the end of the reading... and that means the software could be telling the Lumagen to display the next pattern before the meter is done making a reading. You can look at the timing for these things in MANUAL calibration mode... pick a grayscale step in the software and see how long it takes for the Lumagen to render the pattern completely. CalMAN software has bars that show when the software is communicating with the signal generator and when it is communicating with the meter... those indicators work in manual and auto modes so you can SEE what the software is doing and when. I don't know if your software does that or not -- if it doesn't the job of trying to find out where the problem is gets much harder.
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