How to place colorimeter for calibration? Getting inconsistent data - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 7 Old 05-23-2019, 04:00 PM - Thread Starter
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Question How to place colorimeter for calibration? Getting inconsistent data

I just spent several days calibrating grayscale and then gamma on my JVC RS20 projector, and after spending hours on gamma trying to get the individual R/G/B dialed in I thought I had a nearly perfect flat 2.4 gamma with only a couple of drifts at 10 & 90 IREs on R/B, as well as a near perfect grayscale, almost all <1. BUT, then last night I was basically just going to do a final touchup trying to tame those drifts as well as I could.

After placing the meter in front of the screen again I felt like I got my heart ripped out of my chest when I did a 10pt grayscale test with the same settings I left off with the night before, and both grayscale & gamma were suddenly completely different from what I had just the day before. I then spent a good hour or more just trying to place the meter in different locations to find a good location both trying to get the best Y cd/m values and to see if I could get back to similar grayscale dEs as I had the day before, but no. And not only did I get different results compared to yesterday, but noticed that depending on how I placed the meter I got different dE's & overall data, with R/B values shifting as well depending on location.

I've read different tips that you should try to point the meter close to the viewing angle, and of course try to maximize Y, which is what I did the first time, while of course trying to avoid the meter measuring its shadow on the screen, and I set it up similarly last night as well, but like I said keep getting different data.

I've attached the HCFR files with the results after the calibration, and then from last night from 2 different positions using the exact same settings, but with different results.

As already mentioned, I'm using HCFR, set to rec709 & the recommended color CIE, and using an X-Rite i1Display Pro colorimeter.
Also doing all measurements in as dark as the room gets at night, with no lights on, and we watched a full 2h movie before even starting calibration, so the pj is fully warmed up, and also since I spent an hour+ monkeying with meter placement the meter should certainly be warmed up as well.

Now, I do have a bit of an unusual HT setup, since we're currently using a temporary setup with the pj placed on a nightstand ca 2ft up from the floor behind us, which probably makes it trickier than for most to place the meter in a good spot without getting shadows behind it, not sure if that has something to do with the poor accuracy/consistency I'm getting?

I could definitely use some help & tips on how to get better & more consistent results, since right now I'm not even sure if there's any point calibrating at all if I can't get the same results from one day to the next

Not sure what I can do to fix this?!
Incorrect meter placement?
Maybe incorrect HCFR settings?!
Bad meter? But during a single calibration session I seem to be getting decently consistent results, since I can adjust grayscale gain/offset & gamma RGB values and get it dialed in pretty well.

I've also attached a picture showing how I ended up placing my meter yesterday, I know it probably looks like the meter is pointing right at the shadow in the picture, but it's actually pointing to the left/center of the shadow.
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HT: Stewart 100" 2.35:1 Screen, JVC DLA-RS20 PJ, Kef Reference 205 Front + 202c Center + 201 Back Surround + 208 Subwoofer & Q2DS Side Surround, Denon AVR-3808, Panasonic DMP-BDT320, Roku Ultra, APC UPS, PS3 & PS4, Logitech Driving Force GT Wheel
LR: Panasonic TC-P50UT50 50" Plasma, Kef Q15 Front + Q95c Center, Unknown Boston in-ceiling Surround, Yamaha DSP-A3090, Xbox 360, Denon DVD-2930ci

Last edited by BjornK; 05-23-2019 at 04:05 PM.
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post #2 of 7 Old 05-23-2019, 05:08 PM
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Quote:
Originally Posted by BjornK View Post
I've also attached a picture showing how I ended up placing my meter yesterday, I know it probably looks like the meter is pointing right at the shadow in the picture, but it's actually pointing to the left/center of the shadow.
What kind of screen do you have? Matte white screen is not sensitive to angle, but ALR screens are in general much more sensitive.
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post #3 of 7 Old 05-23-2019, 06:06 PM - Thread Starter
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Quote:
Originally Posted by Dominic Chan View Post
What kind of screen do you have? Matte white screen is not sensitive to angle, but ALR screens are in general much more sensitive.

It's a Stewart 100" 2.35:1 screen, if I remember correctly it's a Firehawk G3 1.25 gain. Not sure if it's considered an ALR screen. I do definitely get much lower Y values if I adjust the angle just slightly, and try to keep the angle at a minimum, which is why I try to place the meter at one side of the measuring window, pointing inwards.

HT: Stewart 100" 2.35:1 Screen, JVC DLA-RS20 PJ, Kef Reference 205 Front + 202c Center + 201 Back Surround + 208 Subwoofer & Q2DS Side Surround, Denon AVR-3808, Panasonic DMP-BDT320, Roku Ultra, APC UPS, PS3 & PS4, Logitech Driving Force GT Wheel
LR: Panasonic TC-P50UT50 50" Plasma, Kef Q15 Front + Q95c Center, Unknown Boston in-ceiling Surround, Yamaha DSP-A3090, Xbox 360, Denon DVD-2930ci
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post #4 of 7 Old 05-23-2019, 06:53 PM
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Quote:
Originally Posted by BjornK View Post
I do definitely get much lower Y values if I adjust the angle just slightly, and try to keep the angle at a minimum, which is why I try to place the meter at one side of the measuring window, pointing inwards.
If you place the meter 2 or 3 feet from the screen you should not need to tilt it.
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post #5 of 7 Old 05-23-2019, 09:01 PM
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Quote:
Originally Posted by BjornK View Post
After placing the meter in front of the screen again I felt like I got my heart ripped out of my chest when I did a 10pt grayscale test with the same settings I left off with the night before, and both grayscale & gamma were suddenly completely different from what I had just the day before.
Yup, same happened to me with my Q9FN. Spend days getting perfect Grayscale & WB (ok, i was on the learnign curve). Got it perfect on Sunday night with an average dE of 0.17. Came back to it on Monday and, omg, it was suddenly all over the place from 50 ire onwards. Didn't make any changes at all and now its consistently bad.

Recalibrated it all last night and hoping it sticks. My new WB settings are now v different from previously.

I have no idea what's going on.

PS i re-profiled my XRite Display Pro 2 with XRite Pro just in case too.
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post #6 of 7 Old 06-05-2019, 08:27 AM
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Quote:
Originally Posted by mombasa123 View Post
Yup, same happened to me with my Q9FN. Spend days getting perfect Grayscale & WB (ok, i was on the learnign curve). Got it perfect on Sunday night with an average dE of 0.17. Came back to it on Monday and, omg, it was suddenly all over the place from 50 ire onwards. Didn't make any changes at all and now its consistently bad.

Recalibrated it all last night and hoping it sticks. My new WB settings are now v different from previously.

I have no idea what's going on.

PS i re-profiled my XRite Display Pro 2 with XRite Pro just in case too.
Just a heads up on Samsungs...I have had several instances where the TV's menu will pollute your readings, even if the menu is not directly in front of the meter. I normally take a reading, make an adjustment, exit the menu, then take another reading. Lots of entering and exiting the menu but it helps!

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post #7 of 7 Old 06-05-2019, 09:59 AM
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If you're using the TV menu to make adjustments it will definitely affect the local dimming and thus the reading. One big reason why I like software like CalMAN that has its own adjustment controls and I don't have to mess with the TV menu.

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