Originally Posted by WilliamG
Thank you for this information. How does 240hz = 25%, and 480hz = 37% duty cycle? I understand the blanking procedure well (which is where the 480hz is beneficial), but I'm unsure as to how 240hz to 480hz is only a 50% increase in duty cycle?
As an example for 30 Hz or 60 Hz 3D input and with the projector operating at 240 Hz, the Sony HW30es will display one black frame between each video frame (or perhaps a better way to is to consider this a transition frame, during which time both lens of the 3D glasses must become opaque). This is necessary since the projector's LCoS chip take some overwrite the previous image with the new image. This isn't an issue with 2D video, but with 3D, where you alternate between right and left images the viewer must not see this transition otherwise there would be lots of 3D crosstalk. Thus the following frames are displayed during 1/60 sec. with each frame being 1/240 sec. long (i.e., refreshed at 240 Hz)
Right image -->blanking frame--->Left image--->blanking frame
Thus for each 1/60 sec. each eye is only seeing one video frame and the other 3/4 of the time it is seeing black giving a 25% duty cycle.
For the 3LCD, using the Epson 480 Hz. chips, they increase the duty cycles by displaying the following frame sequence each 1/60 sec. with each frame only be 1/480 sec. long:
Right image-->Right image-->Right image-->blanking frame-->Left image-->Left image-->Left image-->blanking frame
With this scheme the length of the blanking frame is only 1/2 as long as it is with Sony's 240 Hz projectors. For each 1/60 sec. each eye is seeing a video frame displayed for 3/8 of the time or a duty cycle of 37.5%.