For the brightness measurements the projector was placed upright on a table with the zoom lens at it mid zoom position. This produced an image approximately 61 inches wide from a throw distance of 112 inches. The projector was set to the factory default setting for each of the three Picture Modes and lumens were calculated based on an image with the projector's native 16:10 aspect ratio. The lamp was operated in the High mode, for maximum light output. Below are the measured peak lumens values for each of the VPL-CH375's three Picture Modes.
Sony rates the VPL-CH375 at 5000 lumens, so I checked what the lumens were in the brightest picture mode (i.e., presentation) and with the zoom lens set to it maximum position (shortest throw). In this case I measured 5028 lumens, thus verifying Sony's specification. With the zoom set to its other extreme, i.e., for minimum magnification, the light output dropped to just under 3000 lumens or thus about about a 40% drop.
The VPL-CH375 has 3 lamp settings (High, Standard and Low). As compared to the lumens output in the High Lamp Mode, the light output measured (while operating in Presentation Picture Mode) approximately 25% less in Normal Lamp Mode and 38% less in Low Lamp Mode.
As noted in the earlier section of this review on the picture quality, the factory default settings produced a somewhat "cool" image when viewing video in Standard Picture Mode. I found by reducing the Color Temperature setting from the default "Middle" value to "Low" the picture quality was improved and produced more natural skin colors. I measured the impact on brightness when making this change to color temperature in Standard Picture mode and found that the lumens were reduced by approximately 13%.
The brightness uniformity was checked and approximate a 35% drop-off in brightness has measured near the left corners of the image, as compared to peak brightness near the center of the image. While the light fall-off near the left corners could be visually observed when projecting a full white test image, it was not very obvious when viewing presentations, photos or video material.
We do not measure the noise level produced by projectors. The Sony VPL-CH375 is specified to produce a noise level of 36 dB in High lamp mode, 33 dB in Standard lamp mode and 29 dB in Eco mode. These values, especially in high lamp operating mode, are toward the upper end of what is typical for this class of projector. While the noise level, especially with the lamp operating in high or normal lamp modes, is certainly audible, it should not be distracting to most people when this projector is being used in a business conference room environment. Changing to the “Eco” mode resulted in a noticeable decrease in noise level as compared to high lamp mode and to a level similar to that from a typical home theater projector when such a projector is operating in its normal mode