[Guide] Why Pixels Look Different between 2D and 3D Modes

Discussion in '3DS - Console, Accessories and Hardware' started by NekoMichi, Aug 30, 2017.

  1. NekoMichi

    NekoMichi Retro Collector

    Jun 4, 2015
    Minus World
    (Not sure if this was supposed to go in the tutorials forum, so I've put it in the hardware forum instead. Please let me know if this isn't the right place for this kind of thread.)

    So I read a few threads like this one a while ago about how people found the 3DS graphics to look better in either 2D mode or 3D mode and there was some discussion between the two sides. The aim of this post is not to dictate which is better since this is more of a matter of opinion, however I can give a scientific explanation as to why the pixels look different when you switch between 2D and 3D mode. For this post, I will explain how the 3D technology works, as well as provide microscopic images of the 3DS screen.

    3DS Display - The Basics

    While Nintendo touts the 3DS top screen as having a resolution of 400 x 240, this is only partly true. The image rendered by the 3DS at all times is 400 x 240 dots, however the screen itself actually has a pixel resolution of 800 x 240, with rectangular pixels that are twice as high as their width. The console switches between grouping these pixels together and driving them independently when you switch between 2D and 3D mode. In order to illustrate this, let's look at an image displayed in 2D mode.

    Pixels in 2D Mode

    When the 3D slider is all the way down, the parallax barrier is disabled, meaning that all pixels on the screen are visible to both of our eyes. Under the microscope, the pixel arrangement viewed by either one of our eyes looks like this:

    Pixel arrangement in 2D mode

    The console pairs horizontally adjacent pixels together in the same colour to form one single square dot, effectively halving the horizontal resolution. This results in the final 400 x 240 image we see in 2D. The dot-to-pixel ratio in this case is 1:2.

    Diagram showing pixel arrangement in 2D mode
    Because the gaps between pixels is minimal, they become less apparent to the naked eye. This is why in 2D mode often we see pixels being smoother and blending into each other. Each eye sees a 400 x 240 image rendered by a 800 x 240 resolution matrix.

    Pixels in 3D Mode

    In 3D mode, the 3DS utilises the full 800 x 240 resolution by displaying two separate 400 x 240 images - one for our left eye and one for our right. This effect is achieved by a parallax barrier, which simultaneously blocks one pixel of each pair from being visible to our left eye, and blocks the other pixel of each pair from our right eye. The image seen by one of our eyes looks like this under a microscope:

    Pixel arrangement in 3D mode
    The image is now rendered at a 1:1 dot-to-pixel ratio because pixels are unpaired.

    Diagram showing pixel arrangement in 3D mode
    The individual image seen per eye now has a greater gap between horizontally adjacent pixels, which makes dots easier to distinguish from each other. For some people, this can mean a clearer image while for others this can be perceived as jagginess. A side-effect is a slight change in brightness and/or colour temperature. Because each eye only sees half the number of pixels illuminated in 3D mode as compared to 2D mode, the amount of light that enters the retina should be halved, meaning that the final image would appear darker. Nintendo has taken this into account, and designed the 3DS so that the backlight operates at double the output in 3D mode in order to compensate for this. However this is not always an exact amount and due to manufacturing variations, some consoles will show a slightly darker 3D image while some will seem brighter.

    It should also be noted that the parallax barrier is an on/off digital barrier and not adjustable between different levels. When you slide the 3D slider further up, the system is actually adjusting the camera angles between the images of each eye as opposed to physically shifting a barrier of any kind.

    The Bottom Screen

    Pixel arrangement for the touch screen

    The touch screen of the 3DS does not have this effect because it is always rendering at a 1:1 dot-to-pixel ratio. All pixels are square with equal spacing in between.

    2DS Screens

    While I don't have access to an original 2DS, I do have a N2DS XL for testing, this is what the top screen looks like under a microscope:

    Pixel arrangement of the N2DS XL top screen

    It appears that the N2DS XL outputs at a 800 x 240 resolution, the same as a 3DS in 2D mode. I suspect that the original 2DS would be different and use the same square pixels as the bottom "screen" since technically both displays are on one single panel.

    Other Effects

    Of course, pixel arrangement is not the only factor that affects the final image. In some cases, the rendering engine of the 3DS itself behaves differently when switching between the two modes. The most notable example is in games like The Legend of Zelda: Ocarina of Time 3D, where anti-aliasing is used in 2D mode to smooth out edges between objects, however in 3D mode anti-aliasing is disabled due to processing power limitations, resulting in a sharper (albeit jaggier) image.

    Comparison in anti-aliasing
    Left: Image rendered in 2D mode
    Right: Image rendered in 3D mode

    Some games have also been known to change how the game environment itself is rendered in 3D mode, probably also as a way to compensate for processing capacity limitations.

    The Bottom Line

    While it's technically true that the image quality is different between 2D and 3D mode, which one is better is a matter of opinion. Some people prefer blended pixels while others like sharper images. For many others though, it's not a major issue as the 3DS has a high enough pixel density so that at normal viewing distances the spaces between dots is imperceptible. Either way, it's really up to your which one you prefer.
    Last edited by NekoMichi, Aug 31, 2017
    evandixon, Tanuki_xF and Michu like this.
  2. Kubas_inko

    Kubas_inko "Something funny goes here."

    Feb 3, 2017
    Czech Republic
    I gues on earth.
    Does that mean that N2DSXL has "better/higher" resolution (than 3DS in 2D mode)?
  3. NekoMichi

    NekoMichi Retro Collector

    Jun 4, 2015
    Minus World
    Not necessarily. Even though it has 800 x 240 pixels, the OS isn't using them all individually. Adjacent pixels are still being grouped as one single dot, so the final image is still 400 x 240 dots.
    Last edited by NekoMichi, Sep 4, 2017
  4. HopefulToad

    HopefulToad Newbie

    Aug 25, 2019
    United States
    I don't like this at all. It was obviously a cost-saving measure, to simply reuse the screens from the New 3DS XL sans parallax barrier, but the end result is a very noticeable gap between horizontal rows of pixels, but not vertical columns. And what's more, the gap is even more noticeable when the color being displayed is pure red, green, or blue, because only 1/3 of the pixel is lit. This can be seen pretty well on the green bushes in Super Mario World.

    I don't like the way that looks. In comparison, the bottom screen looks much better to me. I like the New 2DS XL otherwise, but this kind of makes me wish I could transfer back to a regular 2DS. Except the regular 2DS has a mushy D-pad...

    My perfect 3DS system would be a clamshell design with screens the size of the regular 2DS and none of the 800 by 240 nonsense, with the D-pad, buttons, and internals of the New 2DS XL.

    Sorry for bumping an old thread. It's just, I had noticed the horizontal line effect on the New 2DS XL's screen and it bugged me, but I had never found an explanation for it until now.
    NekoMichi likes this.
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