VIVITEK QUMI LED 1280x800 - Page 55

have you seen all the used ones for sale around 440$ on amazon-must be the returns.

Hi all, This is my first post I think and well I've been reading a lot about the qumi and decided to buy it, today it arrived and I've been using it with a 70" da-lite screen, I was intrigued with the fact that a lot of you guy have the focus issue, since this is my first projector, I'm not familiar with this type of devices, anyway, I havent seen my beamer out of focus after 5,10 or so minutes, actually after that time I move the focus ring to make sure that it's focused and i think it is, but what I'm noticing is that even though it's just a 70" screen it's not as sharp as i though it would be, maybe I'm used to my sony bravia 1080p led tv and am kind of spoiled by that, could it be?

I will repeat the question...
I want to buy QUMI. It will be my first projector.
Somebody used (tried, did) instead of the projective screen the screen of a paper background for the photographer? For example: 129 Super White and 172 Dark Gray - bdcompany.com (Excuse, the first messages don't allow to place the link completely)
What reflective properties of such screen from a white or gray background? Whether such background for a projection will approach?
Thanks!
(Excuse for computer translation from Russian on English)

viardo-
Size = 9 x 36 feet roll sheet (2.7 x 10.8 meter)
http://shashinki.com/shop/company-se...et-p-4243.html
super white will make a nice screen-I would stick with white and not grey
blackout cloth works well(thick white curtain liner/Drapery Lining) also

eat meat
Write that on the gray screen above contrast.
At me while only a gray background with the motorized drive. I am going to buy still white and black. Can at someone there was already an experience with a projection on background?

Does anyone turn on/off by pulling the plug? I have mine mounted and would rather do this to avoid pulling out a chair every time to hit the switch. Just wondered if that would be ok or potentially cause problems down the road.

Chad,

It is perfectly fine to do that with this projector as it has no cool down period once turned off unlike all bulb based projectors. I have mine on a power strip and just flip the switch to turn on/off which is bascially the same as pulling the plug.

Mike

Thanks. Figured as much since I've never heard the fans running after turning off.

Does anyone else's opening in the lens look like this?

Hi, mine looks exactly the same. i also see mild light leakage out the left side of the picture. It doesn't bother me since I use it only for TV but might do the ghetto mod trick if I was watching movies.

Thanks zombie, I wonder if the design of that inner part of the lens leads to the light leaking.

Disclaimer: The information in this post reveals certain internal workings and structures related to the Qumi projector. I will under no circumstances take any kind of responsibility wether legally or financially for presenting this information in a public forum or how this information is used by the public. I only present this because it represents the facts and aids in discussion about the projector. I have never been associated with Vivitek or any company related to them.

With the short legal rambings out of the way, here goes. I had 2 Qumi projectors bought directly from retail and then performed a teardown to learn about the internal workings.

The inverted D you mentioned forms the aperture as seen into the exit pupil of the projection lens. The exit pupil is the side that faces the outside so it can be seen directly by everyone. Most people associate apertures as being a perfectly round circle, but this condition does not need to be strictly enforced because most optical systems have focal points at the electronic that are usually some kind of rectangular surface (ie. 35mm film, ccd sensor, microdisplay, you name it)

The aperture shape of the Qumi lens can be seen below:

Within the lens


The actual part


An additional picture for those interested is viewing the lens from the entrance aperture. This is only possible via disassembly, and I estimate the F number is between 2.1 ~ 2.3 (the F number as far as I know has not been publically disclosed by Vivitek)


Anyhow, all the stuff I presented above can only prevent stray light from affecting the picture, and is not the root cause of the light leakage. The inverted D is only one of the attempts to fix the stray light problem.

The real culprit is the right angle prism in the picture below


Those familiar with DLP projection systems will probably know about TIR prisms and RTIR prisms. The right angle prism used in the Qumi looks nothing like the prisms used by more traditional DLP projector architectures. From my perspective, the selection of the prism type works and the prism type chosen is much cheaper than traditional TIR and RTIR types. But as a trade off, it creates a mess with massive amounts of stray light that cripples the ANSI contrast performance if it is not treated properly. This is due to LED light sources being less well collimated than ideal (LEDs are even worse than bulbs) and there is substantial reflection of stray light in the on-state.

The physical mechanism why this is so can be explained by the use of total internal reflection in DLP systems. In addition to the TIR effects, there are also frustrated total internal reflection (FTIR) issues as the 45 degree surface on the prism is undoubedtly AR coated (this causes additional light leakage). Those curious can do the research as to why



I won't speculate wether it was a conscious design decision by Vivitek, but I guess they probably didn't fully anticipate the particularities of a LED light sources when designing the system.

At the end of the day, consumers can only fix this issue using the ghetto mod as shown by others above. To really fix the root cause of the problem requires a huge engineering investment, and thus it is best left to the original manufacturer to figure it out

PS. An engineering solution to the problem is possible

Wow anomaly123, great post! Thanks for the explanation.

Hi guys, you know, at first I liked the beamer, but now I love it, I did a 108" 16:9 DIY screen and and it looks really good, I thought that it didn't have the focus issue at first but now I noticed the problem, but after 5 minutes i just refocused and it works like a charm for the rest of the day, I'm so happy with this projector.

Does anyone knows what is the best cealing mount for this projector? any help will be apreciated, thanks

Hello everybody ,Can you guy confirm? , it 's normal for this projector that we cannot focust to get sharp picture all of image area right ? I already warm up this projector about 10-60 minutes
but picture still blur in some area ,Make me felt up happy.

My PJ scree is 70 inch 16:9

I know this question Already ask ,Please you guy test with Personal Computer or Notebook ,

You will notice the ICON and FONT Got very blury if other part sharp.

Can you focus all of the same time.

I know if you open via media box or cable ,Maybe cannot notice.

This problem is make my eyes pain . And I decide to sell it .

and I hv no chance for claiming due to now I stay in Thailand. (Bought from USA)

Thank you.

I have it plug into one of these 'remote desk lamp' plug that has a wireless remote which basically just cuts off the power to it. Seems to work fine and haven't had any problem with this at all.

I would think any of those security camera mount would do. I bought mine at Amazon. The only down side is that it does have like a 270 degree of freedom so getting it squared off to the screen takes a bit of work but it does work.

This thread was instrumental in my decision to return the new QUMI i purchased for a new one and so I'm returning the favor. I bought and had to return the QUMI not once, but TWICE, receiving a "good" focus unit (with no noticeable chromatic aberration or problems getting uniform focus) on my third try! They have SERIOUS production issues with this!

If you buy a unit and you can't get the whole screen in to perfect focus, return it! It's not some "natural" thing, it's a defect, plain and simple. I almost kept my second one (and i use it as a PC monitor, so the focus flaw was even more noticeable) thinking that if both did this it was just a side effect of DLP technology, perhaps, and I was ready to settle. Well, little tip, it is NOT!

The QUMI is an AWESOME projector, that looks great and promises to be damned useful. BUT if you can't get the entire screen to have the same focus all at once you have a defective unit. Period. Return it immediately! It's okay (to me) that the focus changes slightly as it warms, that's fine. But the focus/chromatic aberration issue is inexcusable (as someone here said, projectors really only have to do a few things and focus is one of them!) and my experience was 2/3rd of them are bad. So be careful about keeping a unit that exhibits any focus problems, and lets all hope vivitek gets their act together because they lost coin on me, that's for sure! Otherwise i'd say this projector is one of the most awesomely cool electronics i've ever purchased -- wow is all i can say. But don't be fooled like I (almost) was!

I hope this helps someone.

ok man, thanks for the tip, I'm going to check them out.

what size screen are you running? I'm at about 106 and do have a slight focus issue on the very top and bottom. It's pretty damn minor though and really is most noticeable during sports when there is a ticker or scorebug in the area that's slightly out of focus. Much, much harder to spot during plain video. I'm not sure it's worth going through the hassle of returning....if I had purchased at a local b&m that would be a different story.

The problem of defocussed/chromatic aberration (LED's being misaligned, perhaps?) I saw at any screen size, and it was noticeable in every screen condition and size. The defect is clearly visible under a magnifying glass to be the red, green, and blue components of each diamond pixel off by a varying amount (1-3 px?) that produces a "floating" plane of perfect focus (i.e. rest unfocussed) that will shift from up to down or left to right as you change the manual focus dial. When your QUMI's screen is in focus, all pixels should look alike when of the same color, as a simple, common sense rule of thumb. Two QUMI's I had failed that test by margins that were obvious when using a PC.

If you have this issue (and a surprising number of people here do) you will know it. It is defective, should be returned (i did).

gotcha, thanks. did you deal directly with vivitek on the returns, or the retailer you purchased from? Maybe I'll get in touch with best buy to see if they would do swaps locally, even though I purchased online. I definitely have the focus issue, but with how it is only minor on the top and bottom.. to me I'm not sure if it's worth a several week or month+ hassle (especially during football season) going through several qumi's looking for a perfect one. Maybe I will just wait till after football is done and contact vivitek. Maybe they will have sorted it out in production by then.

I dealt with the retailer microcenter which was great with the returns. I don't know about waiting though. I did a simple exchange. I doubt they'll do that after the first 7-30 days after purchase, depending on the policy of the store you bought it from. You can always RMA to vivitek (which could be complex), but i wouldn't wait if I got it from a store I could return it to! This advice is to any qumi owner: Do you want an unfocussed projector? Even though no projector worth anything (esp. at $500!) will do? Well, that's all.. enjoy your awesome pico projectors folks! This thread is very helpful!

Thank a lot circlecycle ,You help me very much.

I have noticed it is possible to activate 3d mode also using hdmi input.
All I have done is to connect the vga adapter to the universal port and connect a vga cable to it leaving the other side disconnected, at this point you should be able to activate 3d mode over hdmi using 1024x768 or 1280x720 resolution.
I don't know if the vga cable is needed in order to make it work, maybe it should be working also connecting the vga adapter only.
Obviously the video quality is way better with the hdmi connection

Speaking of 3D does anyone have any video showing the projector in 3d Mode? I know the brightness drops with the glasses on but is it possible to capture that on video or by picture? Sorry don't know the technical aspects around photographing it and obviously it won't show the 3d aspect but wondering if u can capture it for the sake of seeing the brightness drop off.

What hardware are you able to make work via the HDMI connection and in what formats?

Hey guys,

I was looking last night and noticed that I have a very tiny gap at the top of my front lens... is this present on any one else's? I love this thing, but have discovered I do have the floating focus issue. I really don't want to have to return through amazon, I'm probably a few days past now anyway. Ugh.

How difficult is it to take apart and would it be worth it to try and fix the lens?

Thanks guys.

You aren't going to be able to make any determination of brightness from a picture

guys-

please help me.

I need to get into the sevice menu to turn down the saturation and pull out the slight green tint from black /white movies.