Optoma GT720 Projector Calibration and Settings
We calibrate every home theater that we review. The Optoma GT720 received the usual treatment. I "played" with the GT720 for a couple of days, passed it off to Mike for calibration and measurements. 24 hours later, I'm back to watching it.
Ours is a pretty standard calibration, there's always more done by some of the "hi-end" calibrators. Our calibrations, including the Optoma GT720, are normally limited to a grayscale calibration, along with brightness, contrast, color saturation, etc. Only in very special circumstances will we calibrate the individual colors, in which case we discuss why.
7/8/11 - Art Feierman
Let's take a look at the numbers:
Optoma GT720 Color Temperature
Before we provide our settings, lets see what we started out with: Pre calibration, these are the color temperatures over the grayscale range:
Color Temp over IRE Range (Best Mode, Pre calibration):
30 IRE 8172 50 IRE 8142
80 IRE 7685 100 IRE 7718
Standard offered the best looking color, but produced a very cool (bluish) image.
Lumen Output and Color Temp at 100 IRE (mid zoom):
Brightest= 1653 @ 7232
Standard= 1529 @ 7718
Theater= 1296 @ 7891
Dark Room= 839 @ 7993 (By default, Dark Room is on Eco lamp. With Eco off, Dark Room has same lumens as Standard)
User 1= 1108 @ 10280
User 2= 1108 @ 10277
NOTE: There are three other color temps in addition to Mid, but Mid gives the highest lumen output.
GT720 Brightness (Eco Lamp On, Brightest mode): 1306 lumens
That represents a drop from 1653 lumens at full lamp power. The math says that's a drop of an almost perfect 21%. Most projectors drop 20 to 25% when going to their eco - low lamp, power mode.
Optoma GT720 Basic Settings
In addition to calibrating Red Green and Blue for a correct grayscale balance (6500K), there are a number of other settings that come into play. Typically Contrast and Brightness (white balance and black balance), need to be done first. Color saturation and gamma also need adjustment.
Settings for measurements (default values are in parenthesis):
Optoma GT720 Post Calibration Grayscale: Standard Mode
Color Temp over IRE Range (Post calibration):
20 IRE - 6603
30 IRE - 6630
40 IRE - 6642
50 IRE - 6589
60 IRE - 6828
70 IRE - 6626
80 IRE - 6426
90 IRE - 6407
100 IRE – 6321
Average gamma = 2.09
Mike's NOTES: Grayscale calibration is difficult because there is no picture mode where the RGB balance is consistent across the IRE range. This is made more difficult by the fact that the Gain settings mainly affect color saturation (like a Color control) and the Bias settings affect the entire IRE range.
For a better looking Bright mode without affecting lumen output, I would turn down the Red gain to about 10 as was done in the calibrated mode.
Calibration settings for User mode:
Starting settings are from Cinema, but with Brilliant Color on 10, Contrast on 47 and Brightness on 50.
GT720 Post Calibration settings:
Calibration settings for Standard: Color is on 40, all other settings same as pre-calibration or as stated below.
Contrast (Gain) R = (30) 10
G = (30)
B = (30)
Brightness (Bias) R = (0)
G = (0) 2 B = (0) -3
After Mike's calibration of the GT720 he points out that getting the colors to look best in general costs barely 15% of the maximum brightness of this Optoma projector. As such most folks may well prefer our User settings to any of the GT720 defaults.