Acer K335 Projector - Brightness
The Acer K335 is rated at 1000 lumens, which is well above the lumens rating of the typical LED pocket/portable projector. All measurements were taken with the projector displaying an 81” wide image with the projector about 9.5 feet from the screen. Consistent with other reviews, our measurements were taken at the brightest point of the image (usually near the center bottom of the image).
Selecting the 'Bright' picture mode (the brightest), we measured a maximum of 668 lumens, about 33% less than advertised. Using 'Sports' mode, the output dropped to 406 lumens. Next, 'Standard' mode dropped slightly to 387 lumens with 'Game' essentially the equivalent at 377 lumens. All of the above modes have the "Brilliant Color" feature, found on may DLP single chip projectors, turned on by default. 'Movie' and 'Dark Cinema' modes, which were similar in appearance, also were nearly identical in lumens output at 358 and 366 lumens respectively. For those picture modes where 'Brilliant Color' was used by default, turning this feature off reduced the light output significantly. Impacted the greatest was 'Bright' mode which dropped from 668 lumens with 'Brilliant Color' turned on to only 262 lumens with it turned off. The 'Movie' and 'Dark Cinema' modes have 'Brilliant Color' not only turned off by default, but this feature is not available in these mode (I assume because these mode are intended to have more accurate colors).
Somewhat unusual for a mini projector, the K335 has an Eco lamp mode. Using the "Eco" mode reduced the light output by about 15% (measured in 'Bright' mode).
Mini projectors can often have issues with brightness uniformity, resulting in a noticeable drop in brightness from the center of the displayed image to the edges. The K335 performance was fairly good in this regard. The uniformity of the image brightness was measured with the projector operating in 'standard' mode. The maximum light drop off was measured at the top left corner of the image where there was 28% fall-off was measure relative to the center of the image. The other 3 corners of the image showed less brightness fall-off, with a average of about 20%.
Acer K335 Projector - Contrast and Black Level
The specs for the Acer K335 list a 10,000:1 contrast ratio, which if true would made it would have outstanding performance for this class of projector. However, in our evaluation it was immediately apparent that the contrast ratio was far lower than the Acer specification. After verifying the projector's brightness and contrast controls were set to produce the correct reference white and black levels the contrast ratio measured less than 1000:1. When viewing video on the K335 in 'Movie' mode, dark scenes appeared rather flat due to the relatively low contrast and shadow details faded into a grey background. These concerns are not a real issue when using the K335 for business presentations but illustrate one reason why the K335 would not be good choice for watching TV and movies at home.
Acer K335 Projector - Audible Noise
The Acer K335’s LED light source runs cooler than traditional lamp-based projectors and the reduced heat generation allows the two small fans that create air flow through the projector to run relatively quietly. Acer does not provide a dB rating, but it produces a modest noise level in normal operation, but in 'Bright' mode the fan noise increases noticeably. Subjectively, the projector is relatively quiet for its small size and the built-in three watt speaker is able to overcome the fan noise.
Acer K335 Projector - Input Lag
Pocket and Pico projectors are becoming popular for use by video gamers. I checked the input lag on the Acer K335 by connecting the HDMI output from my laptop to the K335's HDMI input and also with the VGA (analog) output of my laptop connected to the VGA input of a desktop monitor. This, and similar tests, actually provide the different in input lag between the connected monitor and the connected projector. This test does yield useful results since the desktop monitor, when using its VGA input, is expected to have a relatively small input lag of only few milliseconds. I tested the Acer K335 in both its 'Bright' mode and in its 'Game' mode and measured similar maximum input lag times in both modes. The maximum input lag observed was 32 milliseconds.