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A very in depth comparison of the Vive and Rift optics (Reddit crosspost)

Zoomie
Level 11
Source - Written by a user named OculusN
As always, it's an opinion piece so YMMV.
I enjoyed reading it.  Hope you guys do too!

"I've had my Vive and Rift now and have been able to compare them directly side by side. This revealed many details to me that no one else to my knowledge has covered. Here they are, but be warned, if you have a Vive or Rift, and you're not bothered by some of the visual defects, then take the language I'm about to put forth with a grain of salt. What I mean by this is that when I say something is "much" better, it is relative. If you're not bothered by the visuals as they are on your headset then you probably won't care much about the differences, and in which case you may or may not care about this post.

FOV:

Let's get this one out of the way real fast, because it's just not that big of a deal really. Honestly, I can't tell much of a difference. The shapes are different, but otherwise I couldn't tell which is bigger. Until we get something like a 40 degree increase, I can't see it mattering much, and this reflects what other people have said, though the Rift does make up for the smaller horizontal and vertical FOV with diagonal since it uses more of the pixels of the display. Still, not really news...

Focus:

So this will be new. The Vive focuses light at somewhere probably 1.3 meters away. The Rift focal length is a bit further away. I have tested this by using negative diopter lenses. What this means is that if you are nearsighted, you MAY be fine using the Vive without glasses, but may have problems if you're so nearsighted that you have to wear glasses all the time in real life. With the Rift, you will want to correct your vision if you are nearsighted, unless you can deal with the slightly out of focus image. Perhaps that could even be preferred, as pixels could be somewhat diffused, but that's a trade-off.

The focus is variable across the lens. On CV1, the center is in most focus, and as you get nearer to the edges of the lens, the amount of focus follows a curve. The center of the lens is in most focus, and in fact it is the only part of the lens focused at infinity. As you get further out, the image gets out of focus a bit, and then dips BACK so that the "focal length" gets closer, probably close to 1.3 meters. I'm unable to scientifically test this, but it may have to do with the layered ridges. If you look REALLY closely at the lens structure, you may be able to see that it is not just a consistent plane of small ridges, but there are "layers" which they reside on. Ridge-ception.

On the other hand, the Vive has more consistent ridges, and the focus curve across the lens is more consistent in one direction. The center is most in focus, and the focus drops off more and more as you get towards the edges.

What this means, at least for what I'm seeing, is that the CV1 produces an overall more "clear" image across the whole lens. The part of the lens that's between the center and the edges where the out of focus section is, is very subtly out of focus. It's not such a big dip. But at the edges, it's indeed very clear, up till you see diffraction blur from the physical edge of the lens holders themselves. The Vive on the other hand does get a lot more blurry at the edges, relative to Rift. In both cases, they are still a lot better than a regular non-fresnel/hybrid lens.

Chromatic aberration:

Both have it, and both are much better in this regard than traditional lenses. However, the Vive has very slightly a bit more, and it is limited to only blue and red. On the Rift, there is actually chromatic aberration in other colors as well, although blue and red are the highest. Overall the chromatic aberration is less noticeable on the Rift. The fact that I can notice, if I really really look for it, chromatic aberration from other colors than just blue and red, on the Rift, means that they're doing something really special with the lens material, or at least the lens material of one of the layers (since we know the Rift lens is composed of two components). They might have designed it so that one component has more chromatic aberration for one set of colors, while the other has less for those colors, but more for others, such that combined, the chromatic aberration for a smaller set of colors is lessened, therefore making chromatic aberration less noticeable overall.

Glare/internal reflections:

This is not the "god ray" artifact I'm talking about. The DK2 and other headsets with traditional non-hybrid/fresnel lenses have this, but to a much lesser degree. This is more of a problem now. It's basically the inversion of the image smeared across the lens, which you may or may not have noticed on the DK2 and other traditional lens headsets. The Rift seems to have slightly more than the Vive, however it is also dependent on eye relief. The more far away you make the lenses, the less glare you get. However, there is more glare "pupil swim" on the Rift than the Vive, meaning that the glare itself will look more different as you move your eyes around than on the Vive, which is potentially distracting if you're particularly sensitive for whatever reason (I'm not). Glare is also less prominent in low contrast scenes.

Eye relief:

This is actually a big topic and a lot of the other factors depend on this. FOV is at the maximum for both the Rift and the Vive at a distance away from the lenses, it is not like traditional optics where you get more and more FOV the closer your eyes are. On the Rift however, that distance is farther, as Doc_ok has revealed, meaning that if you have eyes that jut out of your face more than others (Asian facial structures?) then you might actually want to purchase a VR cover or add some additional padding. On the Vive, it seems to me like the eye relief is adjusted too far out at the default/minimum to get the maximum FOV. The Vive seems like it was certainly better made for glasses users, but now at the cost of FOV due to eye relief, but only for certain people with eyes that are more set into their skulls, like me (I am Asian though). This may depend on facial structure and it may not apply for everyone. Also keep in mind that the Vive lets you adjust the eye relief farther out, if your eyes do jut out more than you'd like or your glasses jut out too much.

God rays:

There may be some relation between this and the glare/internal reflections, but they are definitely separate things. God rays are where the light of the image stretches or is smeared towards or away from the center of the lenses. They should not cross the center. Meaning that if you see an object in the center of the lenses, the light from the object should be scattered across the lens towards the edges, while an object seen at the edge of the lens should have its light spiking towards the center of the lens, but not crossing it. In the latter case, the light you see on the opposite side of the lens is not god rays, but glare, or other internal reflections. I've just taken on "glare" to mean the inverted blurred image, and I'm not sure if there's a better word for it.

The Vive's god rays AND glare follow a pattern where you see the shapes of the ridges come into play, while on the Rift, they're blurred together. In effect, it looks more like you have smudges on the Rift's lenses while on the Vive it feels more solid. I wouldn't actually compare them to film lens flares. They are much worse.

Geometric distortion:

Both have near none, but the Vive has a bit more stretching towards the very close edges.

Pupil swim:

Both perform quite well in this regard for the geometric aspect of pupil swim. Neither does worse. Except for internal reflections, where pupil swim on the Rift seems slightly worse.

Worst case distortions and aberrations:

This is for when you have the lenses in a non-sweetspot. The Rift seems to do worse in geometric distortion. In fact when I first put on the headset without adjusting it much, everything looked weirdly distorted and I felt a bit queasy moving my head around. After I adjusted the headset to get the sweetspot, everything became perfect like it should. The Vive on the other hand doesn't have as much geometric distortion outside of the sweetspot. However, the Vive does blur and focus worse outside of the sweetspot. The sweetspot feels larger on the Rift for blur and focus purposes, but smaller for geometric purposes. Also do note that the Vive does not have a tilt adjustment for the headset, it is just loosely attached to the strap. On the Rift, the tilt between the headset and the straps is held in place, or semi-rigid. This means that you have a bit more options to get a better sweetspot, but ONLY if you adjust it and know what to look for when adjusting. Otherwise the Vive may perform better for those who don't adjust things.

Displays:

They are more similar than people think, even in the mura/tint/brightness aspect. It is more how the displays are tuned. More on that in a second after the small things...

Mura: The Rift has less mura, at least on mine. It is almost impossible to make out neighboring pixel inconsistency on the Rift, while it is very noticeable on the Vive in certain scenes.

Red tint: The Rift has red tinting in certain parts of the displays which are different for each eye since they are separate, and they are more noticeable than on the Vive. The Vive has more consistent red tinting, but it is still present, and it is different on each eye, meaning that it's still very noticeable. Red tinting on either headset is only noticeable when you're in a scene that has near blacks. Because of the brightness boost of near blacks on the Vive, red tinting is less of a problem. But that's a trade-off which will be understood better as I get to the other problems.

SDE: Both headsets have almost none, but on the Vive it is more noticeable and in more types of scenes. On the Rift, it's pretty much not noticeable until you look at near pure black scenes. What SDE means is the linen texture effect. It does not look like a screen door anymore. It is taken to now mean more the feeling of an image on a slightly textured surface. On the Vive, in near pure black scenes, the SDE is much more noticeable. This is a trade-off.

Pixels: Both headsets have visible pixels in scenes where you see a consistent color. However, on the Vive, I'm more able to make out the sub-pixels, while it is more challenging on the Rift. Pixels are more noticeable on the Vive overall. Pixel fill may be higher on the Rift, but this isn't a statement I can confidently make because the magnification itself is different and plays into this. That info would necessarily require some measurement equipment. It just feels like the pixels are less noticeable on the Rift.

Black smear: None in both headsets, but this is because neither turn pixels off in the first place as far as I have seen in any app (although I have been confused before because the Rift came so close a few times to looking like it was doing true blacks, more on that in the next section).

Black levels: Much lower on the Rift. In a scene with pure dark elements and elements of light objectsyou will feel MUCH more like you're looking into a dark abyss, than on the Vive, where the SDE and pixels become prominent. However, this has the negative that you will be able to see the red tint more, and depending on your specific Rift, this can be a huge negative, and in favor of the Vive, depending on if you like noticeable red tinting or noticeable SDE/pixels more. I put the bold thing in bold because once you have something in your vision that is light, your eyes adjust to the light object, and make the red tinted black on the Rift unnoticeable, and look like it was pure darkness, while on the Vive, the lit pixels or SDE never go away in such scenes. This might be hard to visually imagine, but I can assure you that in some scenes, it really stands out and feels like you're truly looking into a dark scene with infinite depths of the unknown, on the Rift, and not on the Vive, but you may not know of what it looks like on the Rift yet or what difference it makes if you haven't seen such a scene and can't compare it to your Vive. It may be perfectly fine on your Vive right now, but when you compare, it stands out clearly. But then again, glare and god rays are present in such scenes, however personally I've been able to ignore those problems just fine so give me dem pure blacks please (but only in the presence of light).

EDIT: To clarify even more, you need more than just a small source of brightness in a dark scene to make the blacks look truly black on the Rift, I would say at least 30% of your vision needs to be filled with something light for that to happen. Also, some people are reporting intense red tinting such that it can be a lot more noticeable, but I have red tinting on my Rift too, and it's not so bad that it detracts from the blacks in such scenes IMO.

Brightness: This isn't so much an end perceived effect that is more preferable, but what causes certain things. The Vive's displays were tuned to be brighter. I will speculate here that it was a decision more than an inherent property of the displays. It is actually noticeably brighter on the Vive, though your eyes might adjust after a while. But back to before, the brightness has nothing to do with dynamic range, meaning that bright things won't look brighter, but the whole image will be brighter. This then means that blacks will look less black, and that plays into the black levels that I talked about. It may have been chosen to do this on the Vive to go partway to solve the red tinting, because the red tinting is certainly there on the Vive, just less visible in the same scenes, where on the other hand the Rift displays truer blacks and less SDE but more red tint.


Whew, that was a handful! Let me reiterate again in case you forgot, but when I said "much better" or something like that, it is only relative, and you may not think so as much. This is from my perspective as someone who likes to get into the nitty gritty.

BUT

What this analysis doesn't reveal is what really matters: the whole experience. IMO, the experience on both headsets is so good that most of these differences are tiny. You won't care much about them, except for maybe one or two depending on you, the individual. For me, I can see past them, no pun intended, and ignore them. However I will say that personally, I do prefer the designs and tradeoffs of the Rift's optics and displays, as well as the visual quality itself. The pure blacks you get to see in SOME scenes just feels like such a luxury sometimes on the Rift, especially in Edge of Nowhere where you do have many of those deep dark abysses (I've tried it before). However, until more content and headsets are released, you might not be able to visually imagine what I'm talking about here in a few circumstances. Certainly IMO many things can be mitigated by well designed content. You won't be noticing god rays much in low contrast. You won't notice red tinting or SDE in brightness.

When I first got into this hobby at the DK2 level 2 years ago, I didn't care much about SDE or pixels or whatever. I just got into the experience. This post probably won't be registered by any of the new users here to mean much, and I admit that when I first started out, a lot of the "nuance" posts and other kinds of posts here didn't mean as much as they do to me now. Hopefully this still provides some insights for a good amount of people."

Any sufficiently advanced technology is indistinguishable from magic. - Arthur C Clarke
16 REPLIES 16

LZoltowski
Volunteer Moderator
Volunteer Moderator
@Zoomie thanks ... I do not read Reddit ... so that is helpful.
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Be kind to one another 🙂

Synthetic
Level 8
try looking 200m  away in VR video.... pixels make it so you cant see that far.... im guessing 100-200m is like the longest you can see.... viewdistance is my main reason against the new headsets

LZoltowski
Volunteer Moderator
Volunteer Moderator
@Synthetic Interesting point ... so beyond 200m distance representative to reality ... you can no longer discern detail?
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Be kind to one another 🙂

Synthetic
Level 8
yer ofc its different distance as its relative.... but you can only see so far until its chunky pixels
old games used to use the viewdistance "fog" 

Zoomie
Level 11
I think he's saying that pixel density limits how far into the distance you can see - as opposed to real life where the quality of your optics (eyes) and atmospheric distortion determine the limit.

I think CV1 is a step-up from DK2.  I notice the limits of pixel density most in driving and flying games where I'm always straining to see the distant corner or a tiny speck of a plane in the sky.  For some people, the pixel density is too low and spoils their experience.  Those people might just have to sit out VR until displays and optics improve.
Any sufficiently advanced technology is indistinguishable from magic. - Arthur C Clarke

Christiaan
Level 4
On the topic of "distance:"

You're ability to determine distance in an HMD with limited resolution is often contextual, or can rely upon methods other than "differential pattern recognition" which fails at nearer draw distances in an HMD than a monitor, or in real life.

If you try the Outerra renderer, even in DK1, you can determine quite well that you are looking at a mountain 1 mile in the distance vs. 2 miles....Their use of atmospheric light scattering and subtle color bias changes gives you a great idea of what's where, out to huge distances.

Some scenes, with less lighting detail, that are relying on stereoscopy, and/or the pattern detail of objects, will look "flattened" as a result. My feeling is that this can be mitigated to a large degree by skillful use of other depth cues, and often times, eliminated altogether.

xWandererx
Level 7
This is probably the Best comparison review I have read on the whole forum. Someone actually explaining how and why certain artifacs exist and whether they have any actual relevence to the wholeVR experience. Ive only ever used a DK2 and I was well impressed by that, reading various user "reviews"......dissing things like screen door effect and tints as if it was the end of VR as we know it, was becoming very offputting. Well done Zoomie for sharing.

DaftnDirect
Volunteer Moderator
Volunteer Moderator
good post Zoomie, I only visit Reddit when I have something in particular to look for, these cross-posts are useful

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Zoomie
Level 11
Thanks for the kind words guys.  Full credit goes to the OP.  If you're on reddit, make sure you upvote him.
Any sufficiently advanced technology is indistinguishable from magic. - Arthur C Clarke