D-ILA Projectors » Reference Series

ID #1305

Will resolution be lost with a 4k projector when using lens memory to view movies in 2.35-1 on a constant height screen? Or does the 4k up conversion make the use of an anamorphic lens obsolete?

Lens memory is an alternative to using an anamorphic lens. They both have their pluses and minuses. However, one of the key benefits of an anamorphic lens for HD projection is significantly minimized when it comes to 4K projection.

Before we discuss how 4K up-scaling plays into it, let’s first tackle the broad question of “losing” resolution with 2.35:1 movies in HD resolution. Many people don’t realize that a 2.35:1 Blu-ray movie with 1920 x 1080 resolution has an active pixel area of only 1920 x 817. The total HD frame is still 1920 x 1080 pixels, but the black bars at the top and the bottom of the image occupy about 263 pixels of the 1080 available vertical pixels in the frame (1080 – 263 = 817 pixels). It’s important to remember Blu-ray widescreen movies only have 1920 x 817 active or viewable pixels to start with.

Now, let’s compare an HD widescreen 2.35:1 movie displayed on an HD projector using lens memory verses a projector using an anamorphic lens. The lens memory configuration will display the full 1920 x 817 resolution exactly at 2.35:1 aspect, pixel for pixel, from the Blu-ray player. No scaling. No artifacts. No distortions. However, the anamorphic setup requires the 817 vertical pixels to be stretched or scaled up to the full 1080 pixels (normally done by the projector electronics). And then the anamorphic lens horizontally stretches the image back to normal aspect ratio. The process of electronic scaling 817 pixels up to 1080 pixels presents more pixels on the screen, but NOT more picture detail. After all, the widescreen frame only had 817 vertical pixels of picture detail to start with.

Okay, back to the 4K element. When 4K up-scaling is performed on an HD widescreen movie it obviously will benefit both the anamorphic lens and the lens memory configurations simply because of higher pixel density and more edge detail (less aliasing, or “jaggies”). However, the marginally higher pixel density that an anamorphic lens offered for HD is not really much of a benefit with 4K projection because of the abundance of pixel density inherent with 4K.

So, now let’s directly answer your two questions:

1) “Will resolution be lost with a 4K projector when using lens memory…?” The answer is “no”.

2) “Does the 4K up conversion make the use of an anamorphic lens obsolete?” The answer is not really, but the higher pixel density of 4K weakens one of the key advantages of an anamorphic lens.

Other advantages of lens memory are the lack of additional lens distortions, and the ability to create a custom lens memory to accommodate closed captioning that is sometimes added onto the black bar at the bottom of the widescreen frame.


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Last update: 2014-04-29 07:35
Author: Ken Bylsma
Revision: 1.0

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