The Panasonic PT-L300U is a “1/4HD” Resolution Wide-screen (16:9)
three-panel LCD-based digital projector aimed at the Home Theater (HT) market. “1/4 HD” means that the
resolution along both axes is 1/2 the resolution of 1080i, the most common
High Definition (HD) format. The L300U therefore has a resolution of 960 x 540,
less than XGA (1024 x 768), but with a true 16x9 aspect ratio LCD shape, so that it is
convenient to use with a 16x9 screen. The other specifications of the L300U
important to the HT enthusiast are 800 ANSI lumens, as well as the ability to easily connect to a variety of HT related video
Inputs and Connectivity
There is a pair of RCA stereo analog audio inputs if you want to have the projector handle both video and sound (in a PowerPoint presentation for example).
The menu system is easy to use. For example, below are shown several menus, such as the main one that comes up when you press the menu button. When you use the up and down buttons to highlight a particular selection, such as Option, and then press Enter, you get the menu for selecting various options that don't need a complete menu page of their own. These include the background color of the OSD (On-Screen Display), where you are placing the projector (for "Desk", the image is right side up, while for "Ceiling", the image is inverted since the projector will be upside down), and lamp power (I used this projector with a Stewart Grayhawk screen, which has a gain of 0.95, so I wanted the "High" setting for lamp power).
The keystone menu lets you adjust the horizontal as well as vertical straightness, so you can place the projector not only below the screen but off to one side. However, it is always better to put the projector in a position that requires only a minimum, or no, keystone adjustments, since you throw away pixels on the sides or top and bottom when you have to use it.
The picture menu lets you adjust all the things that you might want for personal preferences, including color temperature and gamma. Each input has its own memory, so you can adjust each one separately.
The position menu lets you move the image around on the screen, i.e., adjusting the amount of overscan on opposite sides. The Aspect Ratio is also in this menu, and includes 4:3, Zoom (fills a 16:9 screen from a 4:3 original), and 16:9. Each input can be configured separately.
Some of the controls are duplicated on the top of the projector, such as Input and Menu. The Standby/On/Off button is also located here. You can see the small speaker output perforations at the right of the buttons. The left side panel has the main On/Off toggle and a slot for SD Memory Sticks, along with an air intake. The fan blows hot air out the rear.
Although the Panasonic has a DVI input, it apparently
does not support HDCP, so some DVI sources may not work with this projector.
When we evaluate a projector, I not only look at images, I measure the color
balance of the projector at various light intensity levels and determine the
quality of what is called ‘grayscale tracking’. The idea is that black,
white, and all shades of gray, should have the correct ratio of the three
primary colors used in video projection, Red, Green and Blue.
What we see in the above graph above are traces for red, green and blue
which all rise along pretty much the same curve, but with the red curve just
a bit below the others. This indicates that with the color temperature
setting of 2 on the projector, the color temperature was about 500K to 1000K
above the desired color temperature of 6500K. The measured contrast ratio
(IRE 100 window vs. black) was 316:1.
In the color balance chart generated by SMART, we can compare the ratios of
the various colors at the various IRE levels. In this case, the intensity
for the individual colors is compared to the average intensity for that IRE
As can be seen in the above Color Balance graph above, the PT-L300U out of the box, shows remarkably consistent color balance at all IRE levels. This chart also shows that the color temperature is a bit high (red is too low) using the initial setting of 2 on the projector. After these measurements, we lowered the color temperature setting to 1. This seemed to give a color balance (not measured) in subsequent viewing that was much more consistent with the desired color temperature of 6500K or D65.
The other thing we need to look at in more detail is gamma tracking, or how the light output of the projector responds to the input signal. As mentioned above, the relationship between input signal level and light output is not linear, as one might expect, but follows an exponential function. The exponent of this function is referred to as gamma for the display. If the projector tracks the desired function properly, then the image will appear as the director intended, with shadow details preserved at low IRE levels and highlight detail maintained at the high IRE levels. If the projector's gamma tracking is off, then details in the image will either be lost, or the image may look flat and have little contrast.
The chart above shows the gamma tracking behavior for the PT-L300U with the
gamma control on the projector set to 1. In particular, this gamma tracking
graph shows the ratio of the measured combined light level to a theoretical
level calculated, in this case, using a target gamma value of 2.2. If the
projector is accurately producing the intended light intensity level as a
function of IRE level, then the gamma tracking graph will show ratios at all
IRE levels that are close to 1. If the projector is putting out less light
than the ideal, then the gamma tracking chart will proportionally show a
value of less than 1.
- John E. Johnson, Jr. and Steve Smallcombe -