[Mik James]

I am attempting to improve contrast on an Acer K330. The most accessible place to put an iris is between the dmd and the first lens of the lens barrel.

The easiest material to work with would probably be black fabric but I am not sure if this iris placement requires any sort of heat resistance?

I am open to other suggestions as well.

 

[Verge2]

That doesn't really improve your contrast. It's the dynamic part, just buy an ND filter.

 

[Ftoast]

A fixed iris can improve contrast (unlike an NDfilter which can slightly lower contrast..usually about 25%+).
However, the improvement would in the best case be only 1.5X-2X, and will likely be MUCH lower if anything in this case.
Anything inside the projector case will get hot and anything getting hit by light (the iris's job would be collecting stray light) will get hotter..I'd still have no idea how much heat resistance you'll need though.

This sounds like a big task. Even if you ultimately try and fail, I'm looking forward to hearing where this goes if you do decide to continue.
On the other hand, please don't do this if you can't risk the 330..There's a decent chance that something is going to get either melted to something else or that fumes may damage lenses..so don't risk breaking something if you can't spare it.

 

[Mik James]

I already slightly damaged a heatsink. At best I'll get back 200$ on the used market. I suppose that's better than nothing though. I guess i'll just sell it and wait for the celluon picopro. I hate waiting

 

[Ftoast]

I already slightly damaged a heatsink. At best I'll get back 200$ on the used market. I suppose that's better than nothing though. I guess i'll just sell it and wait for the celluon picopro. I hate waiting

I don't see a lumen spec on that celluon, but several years ago Aaxa had a similar (pocket-sized, infinite focus, pure laser, battery-powered) projector and there are a few universal things to look out for.
It will be much dimmer than your 330 was.
It will have laser speckle like those you can see with a laser pointer.
It will have inaccurate colors and white-balance with little/no available adjustment.

Also, until you see it sold online through a standard/major retailer, I'd be wary of the company and how it deals with warranty and support.

 

[Verge2]

A fixed iris can improve contrast (unlike an NDfilter which can slightly lower contrast..usually about 25%+).
However, the improvement would in the best case be only 1.5X-2X, and will likely be MUCH lower if anything in this case.
Anything inside the projector case will get hot and anything getting hit by light (the iris's job would be collecting stray light) will get hotter..I'd still have no idea how much heat resistance you'll need though.

This sounds like a big task. Even if you ultimately try and fail, I'm looking forward to hearing where this goes if you do decide to continue.
On the other hand, please don't do this if you can't risk the 330..There's a decent chance that something is going to get either melted to something else or that fumes may damage lenses..so don't risk breaking something if you can't spare it.

His isn't a fixd iris it's a piece of damn cloth.

I'd be interested in what equipment you used to obtain theses numbers though?

 

[jarrod1937]

A fixed iris is actually better than an ND filter as an ND filter is just lowering light output universally (which can give better blacks though), while an iris is attempting to catch scattered light before it gets focused together with the actual intended image. With that said, all of the parts in a projector are very sensitive and delicate. Slight alterations in position of some components can worsen quality and the slightest knock can hurt a component, so it's definitely not for the faint of heart to attempt this. Likewise, cloth is not a good choice. I accomplished this in an old LCD projector I had which was for parts anyways. I used an iris from an old security camera, it was made of metal, painted black, and from what I could tell was pretty heat resistant. I ended up killing the projector... though only because I was attempting to make a dynamic iris by tapping into the signal output, not the easiest thing to do as a lot of the components are surface mount and the signals going to the panels aren't the easiest to tap into without disrupting the original. You can judge brightness of a scene in LCD's by the power draw used to twist the crystals at the aggregate level.

 

[Verge2]

A fixed iris is actually better than an ND filter as an ND filter is just lowering light output universally (which can give better blacks though), while an iris is attempting to catch scattered light before it gets focused together with the actual intended image. With that said, all of the parts in a projector are very sensitive and delicate. Slight alterations in position of some components can worsen quality and the slightest knock can hurt a component, so it's definitely not for the faint of heart to attempt this. Likewise, cloth is not a good choice. I accomplished this in an old LCD projector I had which was for parts anyways. I used an iris from an old security camera, it was made of metal, painted black, and from what I could tell was pretty heat resistant. I ended up killing the projector... though only because I was attempting to make a dynamic iris by tapping into the signal output, not the easiest thing to do as a lot of the components are surface mount and the signals going to the panels aren't the easiest to tap into without disrupting the original. You can judge brightness of a scene in LCD's by the power draw used to twist the crystals at the aggregate level.

I understand, he's not using an iris man, he's using a piece of damn cloth.

 

[Mik James]

I understand, he's not using an iris man, he's using a piece of damn cloth.

A piece of "damn cloth" which would be in the shape of a cat's eye.
Did you think I was just going to drape some cloth over the lens and call it a day? That would make it a bit tricky to see an image from the projector don't you think?

I'm not going to bother with it. Attaching any sort of iris in their would be quite a bit more difficult than expected due to heat resistance requirements and keeping the light path sealed. It also appears the most effective manual iris implementation is multiple iris' in specific locations, which clearly isn't feasible on this projector.

 

[Mik James]

I don't see a lumen spec on that celluon, but several years ago Aaxa had a similar (pocket-sized, infinite focus, pure laser, battery-powered) projector and there are a few universal things to look out for.
It will be much dimmer than your 330 was.
It will have laser speckle like those you can see with a laser pointer.
It will have inaccurate colors and white-balance with little/no available adjustment.

Also, until you see it sold online through a standard/major retailer, I'd be wary of the company and how it deals with warranty and support.

I'm counting on the dimness, bright enough for me and contrast/mll is king.
I'd guess my current projector is capable of ~300 maximum lumens, closer to 100-150 at my desired settings for ~90" screen, I'm perfectly willing to move the screen size down to a minimum of 50".
From what I have read, lumens scale logarithmicly, so 300 lumens would only double 30.
I've heard they have improved the speckle over the microvision showx, well see how it looks.
My source is a pc allowing for calibration, the 330 isn't exactly reference either.

I'll bide my time though, waiting on reviews.
At the price I would end up paying for this thing it would probably be better to look for a Panasonic Plasma on the used market and wait a few generations until laser is brighter and less speckly or Oled is mainstream.
I might even consider dragging in another Crt Rear Projection set

 

[5h4d0w]

Ha! Somebody else waiting for the PicoPro.

I have to say that their latest promotional video ( https://youtu.be/Al2HApEO43U ) has made me skeptical. Over 200 inch? Yeah right. It has an output of 30 lumen (I've also read 33 somewhere but most places seem to say 30) by the way.

Above, a device by Axaa was mentioned. Which does exist (the "L1") and outputs 20 lumen. It had a much more modest official maximum size at 50". Here's what one Amazon user has to say about that:
http://www.amazon.com/review/R3KFEJ...detail-glance&nodeID=172282&store=electronics

Considering my CRT projector (700 lumen) is just bright enough for 100" in a fully darkened room, I'm afraid that this may be the first display device where even I go "Sorry, not bright enough". -_-

 

[Mik James]

Ha! Somebody else waiting for the PicoPro.

I have to say that their latest promotional video ( https://youtu.be/Al2HApEO43U ) has made me skeptical. Over 200 inch? Yeah right. It has an output of 30 lumen (I've also read 33 somewhere but most places seem to say 30) by the way.

Above, a device by Axaa was mentioned. Which does exist (the "L1") and outputs 20 lumen. It had a much more modest official maximum size at 50". Here's what one Amazon user has to say about that:
http://www.amazon.com/review/R3KFEJ...detail-glance&nodeID=172282&store=electronics

Considering my CRT projector (700 lumen) is just bright enough for 100" in a fully darkened room, I'm afraid that this may be the first display device where even I go "Sorry, not bright enough". -_-

I don't believe the L1 is direct laser, a better comparison would be the microvision show wx and show wx+. Yeah i'd say 60 inches at best in a fully darkened room with a high gain screen.
It's not even about the size of the image for me, if I could find a em focus crt projector or a recent panasonic plasma on the used market here I wouldn't even be considering this projector. The only thing available here with a decent black level at the moment for the price range is bulky crt rear projection sets, and I live on the third floor of an apartment complex

 

[Mik James]

Also, this review of the L1 doesn't really give me much confidence about the lumen spec: http://www.pcmag.com/article2/0,2817,2364150,00.asp

If the picopro can hit an actual perceived 30 lumens it'll be good enough for me.

 

[5h4d0w]

I just realized that you already posted in my PicoAir thread. I think there was no activity for a couple of days, so I stopped watching it. Funny that such a lengthy discussion still developed. Have yet to read it.

I don't believe the L1 is direct laser, a better comparison would be the microvision show wx and show wx+.

Check out the end of this video - looks like black is really black there too:

It's not even about the size of the image for me, if I could find a em focus crt projector or a recent panasonic plasma on the used market here I wouldn't even be considering this projector.

Huh... and here I thought there were still plenty of decent CRT projectors available all across Northern America.

The only thing available here with a decent black level at the moment for the price range is bulky crt rear projection sets, and I live on the third floor of an apartment complex

So? Pay two guys $40 to haul it up there for you if you don't want to do it yourself.

Also, this review of the L1 doesn't really give me much confidence about the lumen spec: http://www.pcmag.com/article2/0,2817,2364150,00.asp

Yes, that doesn't sound good.


By the way, I just measured my current CRT projector and while it may have max. 700 lumen theoretically, I came up with a lot less. I wonder whether made a mistake in my calculations.

I took this here as a guide: http://www.dnp-screens.com/DNP08/Technology/Basic-Visual/What-is-light/Luminance.aspx

To get the following formula (in case somebody will search for this in the future - unless I'm mistaken, this is the formula for converting cd/m² to lumen, assuming a perfect white surface (which distorts my measurement a bit but probably not by more than 5% or so):

cd/m² * 3.14 = lux
lux * area in m² = lumen

So: cd/m² * 3.14 * area m² = lumen

Which resulted in the following for me (screen size 2.11m²):
Projection size 100%: 23 cd/m² => 23 * 3.14 * 2.11 = 152 lumen
Projection size 50%: 36 cd/m² => 36 * 3.14 * 1.05 = 118 lumen
Projection size 10%: 34 cd/m² => 34 * 3.14 * 0.2 = 21 lumen

Hm... I thought that something doesn't seem right about this but now I wonder... is it maybe that the CRT reaches it's max. output per m² at something like 50% (didn't test 60%, 70%, etc.) already, so if the projection window gets even smaller, the output simply doesn't go up any more?

 

[Ftoast]

I'm pretty sure the L1 was also a direct laser..it has infinite focus, speckled, and had no additional imager (LCoS, DLP, LCD) listed.
That's a good point about brightness though. At 50" you'd hit 4ftL with 30lumens which should look solid in a dark room with good blacks and a PC source means you'll have color and gamma controls.
I love my 140-150lm p300 on the 110"-115" screen in a dedicated room which hits about the same 4ftL or maybe a little less, so imagining that with even deeper blacks doesn't sound bad at all.


About my comments for contrast improvements via fixed iris..of the few contrast measurements I've seen that included both wide-open and closed iris measurement, I've not seen a result that beat 2X. I understand there's a lot of differences, I just wanted to make sure OP was aware that while a FI does in fact make an improvement, it shouldn't be expected as anything huge even in the best case and that this particular scenario would likely result in little to no visible improvement. ..and might end in smoke and tears.

Now I kinda want a pocket CRT too.