Brightness
The specs for the PT-RZ670BU list the light output at a very bright 6500 lumens. Now we know that many projectors cannot reach their manufacturer's rated lumens value or if they do that value is only available in a picture mode with such poor colors that it is not a viable option. However, this is not the case with the PT-RZ670BU. I was able to measure just over 7000 in the projector's brightest picture mode (i.e.., Dynamic) and with the lens set for max. zoom. The picture quality with these settings, while not the best this projector has to offer, would be quite acceptable for many applications. However, experience has shown that single chip DLP projectors, especially business and education class models, frequently include a clear segment on their color wheel which allows a very bright full screen white image to be projected but color images may appear much less bright. Thus, this arrangement can provide for very bright black and white images but noticeably less bright color images. This is where the measurement for Color Lumens has been included with some of our more recent reviews. The standard method for determining color lumens is to measure the lumens individually for red, blue and green test patterns then add these lumens values together. With 3 chip projectors, using DLP, LCD or LCoS technology, the Color Lumens will equal the White Lumens. Also for single chip DLP projectors that use color wheels with only red, blue segments, the Color Lumens will equal the White Lumens.
Panasonic has thrown another wrinkle into measuring lumens with the PT-RZ670BU in that it produces images using Red, Blue, Green and Yellow sub-images. Now yellow is not needed for the projector to produce the full spectrum of color (including yellow which is a mixture of Green and Red). Panasonic claims adding yellow allows them to increase the maximum color light output from the projector without the large difference in image brightness between black and white and color images (as is the case for DLP models using white light along with red, blue and green). But before we get into this topic any further, below are the measured White Lumens values taken with the projector's zoom at mid-position, with the laser light source in its brightest mode and with the picture settings at the factory default values.
| Picture Mode |
White Lumens* |
| Dynamic |
6994 |
| Graphic |
6381 |
| Standard |
5595 |
| Cinema |
4786 |
| Natural |
4835 |
| Rec709 |
4835 |
| DICOM SIM. |
4565 |
* These lumens values are for operating in with a 16:10 aspect ratio, which is the native aspect ratio of this projector. When projecting a 16:9 HD video image the total lumens being output will be 10% less.
Changing the zoom lens to its maximum zoom setting increased the lumens to 7071. This may be the highest lumens measured for any projector reviewed by us, so far. This projector's zoom, even at its minimum zoom position, only reduced the max. white lumens to 6773.
But what about color lumens. When I measured for it using the industry standard approach, the maximum color lumens at mid-zoom setting dropped to about 4200 lumens. If the yellow lumens were also included in this calculation, that would get us back up to the value measured for white lumens as reported above.
From my measurements I noted that when the "white gain" setting, in the picture menu, is adjusted not only is the yellow light output varied, but the blue light output is also varied. The Dynamic Mode had elevated levels for yellow and blue light resulting is some image inaccuracies. See below for more information of this. Even with that caveat, the color images projected in dynamic mode had adequately good colors for many applications and were very bright.
The more accurate picture modes measured near 4800 white lumen with their factory default settings and it appeared less yellow light was included in these modes. I noted that the default "white gain" setting was also lower in these more accurate picture modes.
As mentioned above, the Picture Menu has a setting for White Gain. The projector's manual offer little explanation of what this adjustment actually does. When in Dynamic mode the White Gain adjustment has a high default setting while in the more accurate color modes it has a lower setting. It appears when reducing this setting the yellow light level is reduced and also the blue light level is reduced (yellow mixed with blue produces white light). When I operated the projector in dynamic mode while displaying a full white test pattern, I found the white lumens value dropped as I lowered the White Gain setting. Switching over to a blue test pattern, the blue lumens also decreased as I lowered the White Gain setting, but red and green lumens did not change with the White Gain setting. It appears when the White Gain is set to it minimum value (zero) this operates the projector in close to a conventional red, blue, green mode and in this case the white lumens measure around 420o. My overall take on this is using yellow as a forth color plus an increased blue level can help produce a brighter overall image, but at the sacrifice of some color accuracy. With the dynamic mode's default high setting for White Gain, the whites and bright greys appear unusually bright as compared to the most of the color elements within the image.
Contrast
While we usually don't report the contrast ratio of the projectors we test, in this case I did perform a quick measurement for when the projector is operating in Dynamic mode. With the dynamic contrast function turned off I measured an on/off contrast ratio of 1064 and an ANSI contrast ratio of 358:1. Turning the dynamic contrast function back on with a setting of 3 (the default for Dynamic picture mode) the on/off contrast ratio jumped to 9284:1 or essentially meeting the specified 10,000:1 value (it might have reached that spec. value under more ideal testing conditions).
Brightness Uniformity
Brightness uniformity was excellent with a maximum measured light fall off of only about 11% between the center of the image and any of the corners .
