Projector brightness: Optoma EH505 versus Optoma TX785 in 3D and 2D modes

This post compares the light output of two single-chip DLP projectors, running in 2D and 3D mode. These tests were prompted by a perceived reduction in brightness with the EH505 operating in 3D mode.

The projectors were set up in front-projection with 2.5m image width, and room lighting was turned off. The source was HDMI, displaying pure white full frame. For each light measurement, a central area of 200×200 pixels was scanned with an LX1330B lux meter in peak hold mode.

The EH505 projector offers 1920×1200 native resolution in 2D mode, and was tested here at the native resolution, at a custom 3D resolution, and at lower resolution for direct comparison with TX785 (an older model with 1024×768 native resolution). According to the manufacturer, both models are 5000 lumens.

For the EH505, the lamp brightness mode was BRIGHT, the lamp was at about 12 hours life, and firmware version was M01. The 3D mode used for the EH505 was VESA 3D and manually set to Frame Sequential. For the TX785, the 3D mode was set to IR Mode (i.e. DLP-Link mode disabled). Great care was taken to select appropriate settings for all parameters to permit meaningful comparison (there are too many to list here).

For the purposes of the 3D tests, the Full 3D HD 24Hz modes of the EH505 were not used, in preference for true frame sequential active stereo at over 100Hz native input frequency.

Here’s a summary of the results:

ModelResolutionHzModeLux
EH5051520x950104Presentation431
EH5051920x120060Presentation425
EH5051024x76860Presentation435
EH5051920x120060sRGB209
EH5051520x9501043D176
EH5051520x9501043D176
EH5051280x7201203D173
EH5051024x7681203D177
TX7851024x76860Presentation516
TX7851024x76860Bright703
TX7851024x768120Presentation233
TX7851024x768120Bright285

Calculating relative Lumens from Lux and screen area, it appears that the EH505 is about 37% dimmer than the TX785 in 3D mode and about 31% dimmer in 2D mode (these figures are based on a 3.91m² screen area for EH505 and 4.69m² for TX785). In mitigation, the EH505 is of course considerably higher resolution than the TX785. It’s also worth noting that these measurements were only carried out on a single projector.

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