1. If a manufacturer says that the minimum projection distance for a projector is 1.5meters.
Does using a mirror help to reduce the projection distance?
2. Obviously, we can use a smaller mirror if the mirror is placed closer to the projector. Is there any big distortions on the image to compensate for?
Just thinking of a solution for a smaller multi touch table. Those special projectors are still expensive at at the moment.
Most people use mirrors to overcome the manufacturers long throw distance. The smaller the reflected image, the worse the distortion or loss of image quality. Also glass faced mirrors are worse than Front surfaced ones. You can make them from glass mirrors though.
However I haven’t tried myself, it’s only based on what I have read. There shouldn’t be problems though, I have seen people using normal glass front mirrors in their setups happily.
If you are serious about reducing throw distance to minimize table size, you could always take a look at the lumenlab forums, it is actualy quiet hard to increase the throw distance so as a result, their kits have a shorter throw, or if you looked into how it actually works, you could purposely reduce the throw much more.
Most people use the two mirror approach. The mirrors will eventually reduce the lumens by certain percentage. Not forgetting about the diffuser that will eventually reduce the lumens further.
Think I will do with the one mirror way. Guess the table will look more rectangular.
Does anyone know where to get “surface mirrors” with the best efficiency > 95% at an affordable price? How long can this “surface mirrors” last by the way?
I read somewhere where someone used some chemicals to remove the protective layer behind glass mirrors....don’t think the mirrors are gonna last. Its also quite dangerous to do so ya…
We talk about DIY first surface mirrors here: http://nuigroup.com/forums/viewthread/383/. People at the lumenlabs forum have had success with this. Buying a first surface mirror is very expensive, but making one from a normal mirror is not.
Keep in mind that a lot of people here sometimes have a problem with there projector being too bright since the projector is shinning in the direction of the user. So lumen output shouldn’t really be much of a worry.
Point noted. Methylene Chloride sounds like something derived from Methanol. It is actually very bad for the nerve, certain countries ban them in consumer products. People use these stuff in biodiesel.
If it is available try using something based on Ethanol. Though I sense that, it might be slightly expensive.
That aside, how do you guys find the contrast on stuff like Rosco or McMaster?
3M had this propaganda going that says anything rubber blurs the image.
On the brightness, sometimes projectors we see in shops project an image which looks a bit whitish. Think it has something to do with some projector correct?
Could be the projection surface, the contrast, the ambient light… List goes on..
With the stripper in FS mirrors, why not just wear gloves of some kind? Else,if you are worried too much about your health, spend some more money on a FS mirror. Or if you don’t have that money, maybe look at a really thin mirror, maybe made from acrylic.
Hmm, that’s interesting Armage. Although to an extent I’m not surprised a shop would say that since they rather you buy from them then DIY. There’s a number of people on the lumenlab forum, like i said, and also on google that reported that the DIY has worked well. No mention of turning black after a while. It’s probably worth trying on a small mirror since it’s cheap enough. But who knows, maybe they do turn black after a while. Once I get a projector I think i’ll be trying the DIY method first.
cerupcat, don’t get me wrong. THere is some miscomm/ misintepretation here. DIY method = “Using paint remover to remove that layer protecting the metal layer”.
In fact, I asked him if he could remove that layer for me. He was just advising me.
Could be something to do chemical reaction with air (oxidatian)
well, what is expensive whitenoise bought a 50x50 cm first surface mirror for 100 USD i believe
but there is nothing wrong with making ur own first surface mirror, since the projects here are DIY
and to answer the first question, yes a mirror reduces the throw distance
and indeed short throw projectors are pretty expensive, the 3m 700 DMS is about 1750 EUR ex VAT and the Toshiba is a bit cheaper, about 1000 EUR or so, but it has a crappy resolution, and I believe they don’t even produce those anymore
I often did wonder myself about the oxidation once the protective layer was removed myself… and like cerupcat and gravano say, noone who does the DIY method complains about that being a problem.
But I think I could shed some light on that for you. the reflective component of mirrors used to be silver.. which may tarnish black. Now they use aluminum or an alloy. So an aluminum surface wont ever turn black.. unless you submerge it in mercury.. Also if you live close to the ocean, you might want to think about adding a coat of something to it.
I’m calculating the projection distance or actually the angles now.
I have one question: Does the angle of the mirror affect image quality when projecting picture by it? I mean that it is much less than 45°. I’m trying to put the projector to as small box as possible.
Epson EMP-TW2000 can do 30” image from 870mm - i’m not sure if this is the projector to use, but other Epson projectors have similiar throw distances.
EDIT: I attached a PDF which shows the distances and estimated angles. Would it work this way?
i think it depends on the placement of the projector to get a good picture (nonskewed image), my projector only does horizontal keystone alignment, and not even that well. I imagine a software program could help with keystone, but however you are placing the projector, I think that is something to keep in mind-- for any angle other than manufacturing specs will result in a need for slight keystone adjustment. unless i’m wrong here
When a manufacturer lists a minimum image size, does that mean that anything smaller will be out of focus? For example, the Optoma HD70 lists 47.6 inches as the low end of the image size, so what if I want it to be 40 inches? Will it still be in focus?
When a manufacturer lists a minimum image size, does that mean that anything smaller will be out of focus? For example, the Optoma HD70 lists 47.6 inches as the low end of the image size, so what if I want it to be 40 inches? Will it still be in focus?
I did a bit of research with the crappy old projector at my office and it does get blurry as you move closer to the screen. However, by the time it starts losing focus the picture is probably less than 30 diagonal inches (76 centimeters), so unless you are making a very small touchscreen it shouldn’t be a problem.
How long can this “surface mirrors” last by the way?
whitenoise bought a 50x50 cm first surface mirror for 100 USD i believe
