When it comes to VR headsets, one of today’s most noticeable bottlenecks is visual fidelity. When we talk about and compare the visual fidelity of VR headsets we often touch on three key elements: Screen Door Effect, Mura, and Aliasing. Often times we see people mixing these three up, so here’s a quick guide explaining each element and what they actually look like.

Screen Door Effect

In first generation VR headsets like the Rift and Vive, this is perhaps the most noticeable. Technically the result of a display with a low ‘fill factor’, the Screen Door Effect (sometimes abbreviated SDE) gets its name because it often looks as if you’re viewing an image through the fine grid of a screen door.

Photo by Road to VR

Pixels are small, individually lit elements laid out in an array to create a display. For various reasons, pixels are sometimes hard to pack tightly together, resulting in gaps between them which are unlit. A display’s ‘fill factor’ describes how much of the display’s area actually lights up vs. how much is unlit. The unlit spaces between the pixels, which are easy to see on displays with low fill factor, cause the appearance of the Screen Door Effect.


For various reasons, it’s challenging to make each pixel display exactly the same color, even if the computer output to the display is a frame consisting of one singular color value. Mura is the result of poor color and brightness consistency from one pixel to the next.

Here, all the pixels on the display are technically set to one color value, but imperfections in design and manufacturing mean the actual color output can be inconsistent | Photo by Road to VR

Some display technologies have a natural advantage when it comes to color consistency between pixels. LCD for instance tends to be quite good when it comes to minimizing Mura. Other technologies, like OLED (which is favored in VR headsets for other reasons), struggle when it comes to mura, and require careful calibration to achieve decent performance.


Because displays are made up of (generally) square pixels arranged in a grid, it’s easy to display straight horizontal and vertical lines which align with the rows of the pixel grid. But when it comes to displaying diagonal or curved lines, you’re essentially stuck trying to draw a curved line with square blocks that can only be placed along a grid. That means that anything but straight lines will naturally reveal the underlying shape of the pixels and the pixel grid.

Photo by Road to VR

Of course, increasing the pixel density of a display means that aliasing is reduced because the resolution of the display allows the pixels to more precisely fit the curved or diagonal line being rendered.

An example of anti-aliasing used for font smoothing

Anti-aliasing can reduce perceived aliasing by using different colored pixels along the edges of the line to create the appearance of a smoother line.

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These three elements are not the only factors which contribute to the overall sense of clarity when looking through a VR headset, but they are presently among the most noticeable (and thus high on the priority list for next-generation headsets).

Photo by Road to VR

We hope that this simplified explanation will equip our readers with the knowledge to constructively discuss and compare these elements between headsets.

Understanding Pixel Density & Retinal Resolution, and Why It's Important for AR/VR Headsets

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  • Jaap Olsthoorn

    This reddit post talks about OLED Mura and how the new oculus headsets use something called SPUD. I’m not sure exactly how it works, but I do know that my blacks look waaaay better after disabling SPUD and I haven’t experienced any downsides whatsoever. Worth a try for Oculus owners!


  • Thanks for this article.
    The biggest debates in VR I see are about “quality” and what defines it. Everybody has an opinion. Could you also mention:

    * sub-pixel structures (e.g. PSVR vs Vive) and why a lower res device can have less SDE
    * PPI


    • Krzysztof Kiersznicki

      well played some PC vr games on psvr and it was a blurry mess…..arizona sunshine is total crap on psvr…..

      • Peter Hansen

        Would you expect any different result? On release they had a game mode you could only unlock with the latest core i7 CPU. VR games very often are not so well optimized as standard flat-screen games.

        • Jerald Doerr

          The problem with the PSVR is 1st resolution when comparing it to a PC you have to be using a Oculus or Vive which have higher resolution. Even if you used the PSVR HMD on a PC its still going to look the same with the exception for more FPS.

          • Toby Zuijdveld

            Actually super sampling (essentially the best form of anti-aliasing) will minimise that to great effect, especially when considering most PS4 PSVR titles are rendering at a resolution lower than the PSVR can display. The significantly lesser screen door effect could reasonably be considered to heighten the PSVR display to ‘superior’ status as far as first gen headsets goes.

  • impurekind

    Cheers for the explanations.

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  • Behram Patel

    So glad there’s an article on this, here. Thanks Ben.

    The lens magnification exacerbates SDE.

    You could a part two of this article with interjections from Tom Forsythe, Carmack et al.

    That would really put things in perspective.

    • Guest

      Those guys were kids playing with games during the previous VR wave of the 90’s. One of them is still pushing anti-aliasing and that’s the worst thing for OLED’s

      • Toby Zuijdveld

        Well that just doesn’t make any sense at all. The most crisp looking PSVR games are those that supersample.

  • Nissim Hadar

    I love that the “Shop Related Products” are for screen doors :)

  • victor

    hmmm… funny for me the awful FOV is the biggest issue today inVR. Erveryone must indeed see the world differently. I guess in day-to-day lviving some people rely on details while others rely more in peripheral vision

    • benz145

      We all want more FOV : ).

      I mentioned that these factors are key contributors to visual fidelity/clarity. Field of View is important for immersion but it has little to do with clarity. That is to say, this article’s goal was to help people differentiate these three things, not suggest that they are the only important aspects of a VR headset.

  • Lucidfeuer

    It’s really odd: I’ve never been able to notice Mura as much as I’ve been able to distinguish “Led Curtain Effect” on high-resolution OLED…I don’t think the eye can spot such color discrepancies, but you can clearly see the wall of RGB leds.

    • crim3

      The mura effect is very prominent in dark scenes

  • oompah

    Most of problems can be avoided using
    Ray tracing using MLT or Energy optimised graphics
    However these r difficult to achieve as of now
    but I propose a 2 way solution using foveated tech:
    1.Let the scene be painted normally for the area other than the central image
    2. The Central small image (say 20%) be foveated ,painted using Ray tracing realistically & u avoid these above problems but also achieve :
    realistic shadows,
    Refraction etc
    And many many fans & customers who’d junk the rest
    And I believe this is to be achieved by hard baking both technologies onto chips simultaneously (for each eye) .
    I think that Qualcomm etc should seriously start designing these now
    (wish I was Jeff Bezos or something , I’d create a VR which would make ppl forget the real reality)

    • Neither foveated rendering or raytracing will have ANY effect on these three artefacts, which are display hardware issues. Multisampling does reduce aliasing, but you can multisample already without raytracing.

      Splitting the render pipe into a chip per eye (assuming some imaginary new dedicated hardware) wouldn’t help much either because you’d be using double the power and cost, but wasting most of it because seperate chips would make it far harder to share work between left and right eyes.

      • Jerald Doerr

        Yup you’re right that’s what I think Pimax is doing right with 2 HDMI ports on the high-end unit. A video card per screen would be awesome. If anyone wants a nice HMD thats going to take everyone else 3 + years to make buy the end of this year..

  • Surykaty

    Long time ago I tried to ask about Mura (had no idea it was called like that back then) because it was really distracting to me (super sensitive eyes after working with graphics for 20 years) and non of the Oculus devs actually knew what I’m talking about.. they couldn’t comprehend the idea that pixels actually vary quite alot even though they should show the same color/L value. Fun times all those years back.

  • Luke

    I wish more vertical fov other than horizontal fov.
    in echo arena sometimes I can’t see my hands because the vertical fov is not enough large.
    the same in onward, I wish to see more stuff simply looking down with my eyes….

  • Great post, simple and effective. As always, Ben, you made a great job!