This will be interesting to test. Point is it is 700PPI display. So that means SDE should be near to Pimax 4K which is 800PPI and for comparison Deepoon E2 is around 550PPI. So SDE should be more close to Pimax 4K.
I’ve been thinking about this and I think that PPI doesn’t say much. For example Kopin are producing extremely small panels, so the PPI of those panels will be very high: 2940 PPI !! But since these panels are so small, the FoV is very small too. Kopin says they’re solving this with special lenses to get to 100 degrees FoV. But this then means that the amount of pixels in the virtual image that your eyes see is WAY lower.
So it’s not about the PPI of the display, it’s about the PPI of the virtual image that the lenses create. So I don’t think PPI of the display means much when it comes to VR. And a lower PPI panel could be much more suitable for VR than an extremely high PPI panel, because it might be very difficult to get a reasonable FoV on those panels.
It is proven, PPI is only real measure for predict SDE. On SDE resolution not have effect at all. PPI is phisical resolution on reai inch. ON PPI inch is an inch.
This is explain with printing but on screens is similar situation.
More PPI more sharp picture with smaller grills. for SDE similar like this pixelate print in this video.
So PPI is only relevant for SDE.
If you compare this video …
Vive/CV1 have around 460 PPI
E2 around 550 Pimax B have similar PPI but it is OLED
Pimax4k around 800 PPI
visual diference is exact as diference in PPI.
3 Likes
They use about the same lenses I guess. My point is, the display PPI is totally irrelevant without considering the lenses: What really matters is the PPI of the image that the lenses create. See Kopin: they create 2k*2k panels with almost 3000 PPI. According to your theory these should have amazing good SDE, actually not visible at all since it’s 4x higher than Pimax 4k PPI, right ? Now imagine you put lenses in it that can create 200 FoV. The resulting ‘virtual image’ will have lower PPI than the Pimax 4k, so more SDE ! This because the same amount of pixels are spread out over a much larger virtual image.
3 Likes
Only if you comparing SDE. Other display have better refresh rate and better color so all this is individual experience do you prefere SDE over gosting and vivid picture. This last video prove every tehnical aspects of this VR’s. It is effecting on motion seeknes as well whot is strictly individual aspect which is based on contradiction of visual wizh sens in middle ear and ir is fading with time when your brain got more experience (data) to compare and level it with balance sense from middle ear.
1 Like
Actually thinking of it, it’s really easy: what matters is the resolution spread over the FoV ! If you have a screen that has 1.5x higher resolution but has 2.0x higher FoV, then the SDE will be worse.
The PPI doesn’t matter here. Kopin has 22k2k panels, so effectively exactly 4k, at 3000 PPI and 100 FoV. Pimax 4k has a 4k panel at 800 PPI, but has 110 (?) FoV. So the Kopin SDE will only be slightly better, even though it has 4x higher PPI.
If the Pimax (800 PPI) and the Kopin (3000 PPI) had the same FoV, the SDE would be exactly the same !
FOV don’t have nothing with PPI. I believe you got something wrong or someone pass it to the press with mixed or wrong references. It will not be a first time. All today’s VR even cardboard have same magnification lenses. Only different is in size what effecting on FOV.
Point with smaller screen you need higher magnification approximate to size of the screen so twice smaller display need twice higher PPI.
About 3000PPI it must be some SF revolutionary technology out of this planet. This 3000PPI is not possible with todays LCD technology.
There you go
More technical.
It is actually same shit as PPI only sound fancy and like Apple invent hot water again.
OK. And how do you know that have real 2940PPI and high SDE in use?
So if it is true because of the display size need to be magnified 3x higher than “regular” VR display but still it is higher than 800PPI but not much more than 1000PPI if we translate masure after magnification. But this rase question of optic quality. This could have possible more distortion picture on periferal something like fisheye or if we use Fresnel lenses more problem with God rays.
We can’t know nothing before first proper reviews.
It’s actually really simple. Imagine you have the pimax display panel right ? Now shrink it half in size. You have now 1600 ppi right ? It’s still 4k resolution though ! So to display it you now need to magnify twice. The result will be the exact same image, yet the DPI of the panel is two times higher.
DPI says nothing because it’s a function of panel size and panel size is irrelevant to the user (as long as the lenses can “translate” (magnify) it correctly). You shrink a panel in half so you get two time higher PPI ? Well that’s great but now you need to magnify twice 
So the net result is 0.
DPI is irrelevant. It’s all about panel resolution (and FoV).
Oh and what matters somewhat too is the amount of used pixels. For example, the Pimax uses soft IPD, so they move two circles around the display, according to the IPD: the higher the IPD, the more space between the two circles (one circle for each eye being displayed). Only those 2 circles get picked up by the lenses though ! So there are relatively a lot of pixels that are NOT used for the final resulting image. So effectively this lowers the resolution.
Now imagine you have a square 2k*2k panel like Kopin made. Put two of them in a HMD, one for each eye and use hardware IPD to move them: this doesnt cause any lost pixels. So this will also be better for the SDE and picture fidelity.
Of course there are still lost pixels though, since the screen is square and the lenses are round, so you still effectively have lower real resolution than the panel resolution.
But the loss is smaller when you have hardware IPD.
Or in a picture:
Only the yellow pixels will be used and the blue pixes are wasted ! So hardware IPD is a lot better for the SDE and image fidelity than soft IPD, but only of course if square display’s are being used !
Actually this raises the question: which form factor will the Pimax 8k panels have ? Because if they’re regular panel size, the ‘waste’ is enormous. In fact, you’ll get this:
So the resulting SDE will be a LOT higher on the Pimax 8k than on the Pimax 4k if the panels are not square, due to huge unused panel parts. UNLESS somehow special lenses can be used. Maybe the fresnel lenses overcome this problem and make more oval than circle projected parts ? Hmmm thinking of this, it almost must be that with special lenses they create oval images. Because if not, it would be useless to use 2 panels (because the size of the circles doesnt increase). So I’m guessing the Pimax 8k lenses work like this:
Would love to hear more about this @PimaxVR ! Or maybe @crony has some input ? But yeah I think it works like this and that this is also THE reason Pimax moved onto their own renderer, because the image ‘distortion’ is a lot different (oval instead of round circle) and they need a custom renderer/distortion to create this.
2 Likes
It is up to the HMD developer to choose what to do.
I prefer a square lens because I hate pixel waste.
2 Likes
You are mixing PPI with DPI. DPI is actually native resolution of display. In Pimax case it is 2560x1440 because 4K is not supported yet.
With some basic mathematics and knowledge of Pythagorean theorem you can calculate exact size of display and how much magnification you need for reach desired FOV.
That is why for example Microsoft MR have higher SDE compared to Vive/CV1 even have higher PPI but smaller display and need higher magnification which increasing SDE canceling PPI advantage.
IPD dont have nothing with SDE. Fact that with proper IPD you notice SDE better is because better and sharper picture in general with proper IPD.
Also 8K problem will be if they use standard lenses. Even Fresnel lenses, which will be implemented in 8K, are not perfect solution.
For VR we will need some special made progressive lenses which will be made for exact task needed in VR. Standard lenses which now use all VR are made for some general purpose not have im minde to fix some specific needs VR have. But that will increase significantly cost of the HMD.
I did mistype DPI when I meant PPI indeed. We’re talking about displays so we’re talking pixels, not dots 
Yes, that’s indeed exactly my point. PPI says nothing in itself. If you make an extremely small 1k display panel, you have extremely high PPI but still only 1k in pixels available to create the HMD image, so horrible SDE. It’s all about resolution and the FoV; we should not consider PPI for VR as a valid parameter.
Please take a look again at the pictures above. In the very first picture there’s a lot of blue area between the 2 lenses, which are “wasted” pixels, They’re just being used a ‘IPD adjustment zone’ and not for display: if the user selects lower IPD, the displayed area’s (the yellow circles) move to the center and vice versa. So the actual pixels that are left to create the HMD image (the pixels inside the yellow lenses) are actually way lower. So that’s why soft IPD causes more SDE than hardware IPD (IF of course the panel size conforms to the lense size). Just compare the blue area in the first 2 picture’s, that’s my whole point.
I think you’re using an online translator right ? I think a part of my explanation got lost in translation. A last picture then to explain:
this is what happens when you adjust the IPD parameter, it just moves the circles around the display. But a lot of display pixels are unused for the HMD picture = worse SDE.
2 Likes
I don’t have time to debate about it with you but your assumptions are completely wrong and are not based on facts but wrong interpretation of some aspect. of VR. This debate is pointless when you don’t want to see what I’m talking about.
You are valuable member here on this forum and I respect that, in fact one of the most active with lot of good thing you done for community. Don’t get me wrong but with all my respect to you this time you are wrong.
Just answer one question, if you are right hows that that SDE is increasing with decreasing of PPI?
From what i understand he’s referring to 3 factors.
- size of panel
- ppi of panel
- amount of magnification to give equal fov
Example 5" panel with 800ppi vs dual 1.5" with say 800ppi per panel for combined 1600dpi.
So lets say 5" panel has focus 1 to get 100°Fov.
The dual 1.5" panels would require 2x focus/magnification to get 100°Fov.
If i understand correctly the sde effect would be equal in both setups.
Now with having a single 5" panel with soft ipd there is more wasted/unused area the panel vs dual 1.5" panel.
The dual panel will have less sde due to less screen waste in binocular vr.
1 Like
Someone needs to declare a new metric, Pixels Per Degree, or PPD. Might need a vertical and horizontal measurement.
1 Like
Ok let’s do it with an example then. My science teacher always said that a lot of times it’s easier to understand something when you take extreme value’s. So let’s do that:
Imagine an old school cellphone, one with tons of visible pixels, let’s say a display of 300x300 resolution, so extremely low resolution. Now imagine that with some new procedure someone can print such a display on an extremely small panel, say 0.01*0.01 inch. What PPI would such a panel have ? You’d need to calculate the diagonal panel length first with pythagoras: v(0.01 ^2 + 0.01 ^2) = 0.014 inch. Now enter the info in a PPI calculator like this: https://www.sven.de/dpi/ and you end up with a whopping 30304 PPI !! Now imagine that with some specific lens you can zoom this image enough so that you can show it in a VR headset. How do you imagine that this will look ? Remember that on the panel are still only 300x300 pixels available to make the image so you seen tons of pixels !
I’m really not sure how to explain this better. But PPI is a function of panel size and resolution. The smaller the panel, the higher the PPI (given the same resolution). But a smaller panel for VR just means you need to zoom more ! So PPI is irrelevant. What counts to the user is that he only has 300x300 pixels available to make up the image ! So it’s all about resolution.
Remember that we’re talking VR here, looking through a lens. If you look without a lens, sure, the higher the PPI the less pixels you see. But in VR, through a lens, you have to zoom to show a complete image to the user. So the smaller the panel, the more you have to zoom. And zooming means pixels become better visible.
2 Likes
PPI is pixel per inch. That inch is same size on 5" or 50" screen. That is the point
I explain it already but repeat now again and will use E3 and HP/ACER VR. Deepoon E3 have 2560x1440 resolution with around 550PPI on 5.5" size. HP/ACER VR got dual 1440x1440, 550PPI on 2.8" diagonal. Combined this two display give you 2880x1440, 550PPI 4.7", This 4.7 you can calculate using basic Pythagorean theorem. So PPI id same but even with better resolution HP/ACER to reachsame level of FOV and visible picture need higher magnified lenses. So if it is 20% higher magnification that increasing SDE as well for that 20%.
That is confirmed on testing where guy who was testing it and compare with CV1 say’s that why CV1 give less SDE.
