Why you should consider using a spectroradiometer instead of a pod device?
  • Aren't Pods Faster? - The pod tested and its software are sometimes faster and sometimes slower.  Both will slow down on dark images when you activate the improved accuracy mode in i1 Pro DCS.  A typical measurement sequence required five more seconds for the Eye-One Pro than the color analyzer.  What good is fast if it is wrong even if the pod is slightly faster ? 
  • Aren't Pods Better In Low Light? - Maybe if you are not using i1 Pro DCS, but it is not obvious in any of the data below when compared to this software.  Note the amazing performance of the Eye-One on the Sony B&W monitor even at 0.03 fL the values are believable while the pod is erroneous with an impossible reading of 0.9 in x. 
  • Aren't Pods Acceptable For All Display Types? - You could say that, but what does that mean.  Take a look at the data below and see if you believe a pod is acceptable.
  • Won't a spectroradiometer miss narrow emission bands? - Look at the green and red laser pointer data below to see how the GretagMacbeth i1 Pro responds to these extreme measurements versus the pod.
  • Why would a spectroradiometer be better than a pod?  - A pod measures light through filters and estimates the color based on a relatively small number of sensors, usually three and sometimes a few more.  The i1 Pro uses a holographic diffraction grating with a diode array (no filters to degrade) similar to what is found in laboratory grade instruments.  The i1 Pro samples with 100 sensors instead of three and uses the internationally recognized scientific standard method from CIE to calculate the x and y coordinates from those samples.  Which do you think is likely to be more accurate?
 

 

The following tables compare measurements made with a GretagMacbeth i1 Pro using the i1 Pro DCS software with improved low light capabilities (only available from AccuCal™) versus a popular professional color analyzer probe.  Note the large difference in foot Lamberts (fL) measured with the rear projection televisions.  The pod does not see the screen gain and reports a value that is too low.  

Note that the pod is reasonable for the direct view CRT which is what they were used for historically.  ±0.005 in x and y is the target accuracy for many color calibrators.

Definitions:

  • Signal = Input signal strength to the display.
  • x = x coordinate (0 to 1) in the CIE 1931 color system.  The larger the value the redder the color.
  • y = y coordinate (0 to 1) in the CIE 1931 color system.  The larger the value the greener the color.
  • Y = luminance in foot Lamberts.  This is how bright the display is.
   
  LCD Rear Projection Display Results:
   
 
  i1 Pro Sensor     Popular Pod      
                 
Signal x y Y,fL x y Y,fL diff. x diff. y % diff. Y
0 0.2650 0.2518 0.159 0.2725 0.2463 0.056 0.0075 0.0055 65%
10 0.2682 0.2693 0.274 0.2712 0.2627 0.0960 0.0030 0.0066 65%
20 0.2971 0.3020 0.785 0.2924 0.2877 0.2170 0.0047 0.0143 72%
30 0.3103 0.3182 1.826 0.3025 0.3040 0.4740 0.0078 0.0142 74%
40 0.3177 0.3285 3.570 0.3084 0.3129 0.8630 0.0093 0.0156 76%
50 0.3208 0.3315 6.055 0.3137 0.3141 1.4450 0.0071 0.0174 76%
60 0.3220 0.3316 9.159 0.3152 0.3172 2.1830 0.0068 0.0144 76%
70 0.3220 0.3316 13.109 0.3157 0.3168 3.1290 0.0063 0.0148 76%
80 0.3228 0.3336 17.891 0.3153 0.3167 4.3320 0.0075 0.0169 76%
90 0.3234 0.3350 23.053 0.3162 0.3184 5.6370 0.0072 0.0166 76%
100 0.3241 0.3381 28.422 0.3168 0.3195 7.1810 0.0073 0.0186 75%
Red 0.6458 0.3269   0.6433 0.3311   0.0025 0.0042  
Green 0.3029 0.6689   0.2845 0.6685   0.0184 0.0004  
Blue 0.1491 0.0638   0.1462 0.0596   0.0029 0.0042  
        Average Absolute 0.0073 0.0126 75%
        Difference Excluding 0% & 10% Signal  
   
  LCoS Rear Projection Display Results:
   
 
  i1 Pro Sensor     Popular Pod      
                 
Signal x y Y,fL x y Y,fL diff. x diff. y % diff. Y
0 0.2757 0.2619 0.112 0.3000 0.2562 0.04 0.0243 0.0057 64%
10 0.2962 0.3057 1.017 0.2683 0.3328 0.3290 0.0279 0.0271 68%
20 0.2930 0.3009 4.492 0.2732 0.3055 1.4220 0.0198 0.0046 68%
30 0.2925 0.2998 10.453 0.2756 0.2943 3.3850 0.0169 0.0055 68%
40 0.2934 0.3006 19.397 0.2772 0.2899 6.1740 0.0162 0.0107 68%
50 0.2925 0.2970 31.070 0.2790 0.2880 9.9180 0.0135 0.0090 68%
60 0.2926 0.2978 46.236 0.2784 0.2867 14.6170 0.0142 0.0111 68%
70 0.2937 0.2981 64.465 0.2798 0.2841 20.4630 0.0139 0.0140 68%
80 0.2943 0.2952 86.728 0.2807 0.2824 27.2370 0.0136 0.0128 69%
90 0.2944 0.2956 110.825 0.2808 0.2806 35.1880 0.0136 0.0150 68%
100 0.2928 0.2949 138.362 0.2826 0.2800 44.2640 0.0102 0.0149 68%
Red 0.6664 0.3292   0.6655 0.3302   0.0009 0.0010  
Green 0.2900 0.6295   0.2853 0.6170   0.0047 0.0125  
Blue 0.1461 0.0507   0.1443 0.0475   0.0018 0.0032  
        Average Absolute 0.0116 0.0095 68%
        Difference Excluding 0% & 10% Signal  
   
  B&W D65 CRT Results:
   
 
  i1 Pro Sensor     Popular Pod      
                 
Signal x y Y,fL x y Y,fL diff. x diff. y % diff. fL
0 0.3512 0.3522 0.030 0.9023 0.0446 0 0.5511 0.3076 100%
10 0.3278 0.3431 0.099 0.3247 0.3475 0.0570 0.0031 0.0044 42%
20 0.3166 0.3452 0.367 0.3181 0.3503 0.2900 0.0015 0.0051 21%
30 0.3151 0.3448 0.997 0.3172 0.3490 0.8850 0.0021 0.0042 11%
40 0.3156 0.3438 2.106 0.3177 0.3474 1.9460 0.0021 0.0036 8%
50 0.3162 0.3438 3.748 0.3176 0.3474 3.5690 0.0014 0.0036 5%
60 0.3164 0.3431 5.900 0.3179 0.3464 5.7200 0.0015 0.0033 3%
70 0.3166 0.3430 8.594 0.3181 0.3459 8.4240 0.0015 0.0029 2%
80 0.3167 0.3426 11.808 0.3186 0.3454 11.6750 0.0019 0.0028 1%
90 0.3173 0.3425 15.612 0.3192 0.3452 15.5430 0.0019 0.0027 0%
100 0.3171 0.3422 19.754 0.3199 0.3450 19.8470 0.0028 0.0028 0%
Red - -   - -   - -  
Green - -   - -   - -  
Blue - -   - -   - -  
        Average Absolute 0.0018 0.0035 6%
        Difference Excluding 0% & 10% Signal  
   
  Color CRT Results:
   
 
  i1 Pro Sensor     Popular Pod      
                 
Signal x y Y,fL x y Y,fL diff. x diff. y % diff. fL
0 0.4232 0.3655 0.019 0.1953 0.4365 0 0.2279 0.0710 100%
10 0.3111 0.3085 0.244 0.3144 0.2973 0.2170 0.0033 0.0112 11%
20 0.3058 0.3229 1.354 0.3074 0.3191 1.3050 0.0016 0.0038 4%
30 0.3045 0.3291 3.490 0.3052 0.3248 3.3870 0.0007 0.0043 3%
40 0.3030 0.3293 6.576 0.3047 0.3263 6.4450 0.0017 0.0030 2%
50 0.3021 0.3300 10.677 0.3049 0.3266 10.4950 0.0028 0.0034 2%
60 0.3031 0.3303 15.734 0.3056 0.3264 15.4540 0.0025 0.0039 2%
70 0.3038 0.3302 21.593 0.3066 0.3262 21.2570 0.0028 0.0040 2%
80 0.3046 0.3299 28.257 0.3079 0.3259 27.8290 0.0033 0.0040 2%
90 0.3062 0.3298 35.729 0.3095 0.3255 35.1790 0.0033 0.0043 2%
100 0.3077 0.3296 43.750 0.3112 0.3252 43.0840 0.0035 0.0044 2%
Red 0.6035 0.3372   0.6042 0.3363   0.0007 0.0009  
Green 0.2848 0.5738   0.2745 0.5725   0.0103 0.0013  
Blue 0.1520 0.0776   0.1536 0.0735   0.0016 0.0041  
        Average Absolute 0.0029 0.0035 2%
        Difference Excluding 0% & 10% Signal  
   
   

Tests have also been done in illumination mode measuring the light meter performance of the Eye-One Pro with a diffuser versus an AEMC  CA813 meter.  The Eye-One Pro showed exceptional agreement with the AEMC meter.  This will allow a front projector owner to calculate his actual projector light output using the following relationship.

    1 Lux = 1 Lumen/Square Meter

Front projector calibration with the diffuser also allows accurate color measurements down to a 0% signal level in many cases using an i1 Pro DCS. 

 
   
  Test Notes:  All measurements were made after each display had been warmed at least 15 minutes.  The same signal generator, input and cabling was used for all tests with each instrument.  Ambient light was held to a minimum in each case.  The color analyzer probe was tested before and after the i1 Pro and the test that compared the best with the i1 Pro was chosen.  The differences observed by testing before and after were relatively small compared to the overall error observed.  The color analyzer probe was last calibrated in April 2005 and the i1 Pro was certified in February 2005 both of which are well within the manufactures recommended frequency at the time of these tests.  The Sony PVM-96 did not appear to be at D65, but was slightly green as both measurements correctly indicated at higher light levels.  This color error was corrected by replacing the worn tube with a new one.

Pro AV magazine did a test of various colorimeters demonstrating the difficulties with these types of measurements.
 

HOME | ABOUT US | SERVICES | PRICING | SOFTWARE | CALIBRATION | SEEN IN
FAQ | LINKS | REVIEWS | GLOSSARY | CONTACT

© COPYRIGHT 2007 AccuCal, Privacy Policy