There is nothing wrong with the 2 prisms lenses we have been able to make from the knowledge found here...
Mark 🙂
Mark 🙂
Mark Techer said:
Didn't mean to imply there was, I think 2 look fantastic... hense why I feel I will have 2 of my 4 soon for sale 🙂 I'm certainly not letting them all go!
So does any one want to volunteer their expertise on refractive indecies for different types of glass?
If we go back to the original liquid filled DIY lenses from 2002, you might remember that they were filled with Water (in 1 prism @ 30 degrees) and Turpentine Oil (in the second prism @ 24 degrees).
Their refractive indexes are as follows-
Water (20° C) 1.33283
Turpentine 1.472 [there is no listing for Turpentine oil, but common household terps is oil based anyway]
I've dismissed the theory for the need for varying prisms angles as by default, the angles for the HE lens are positioned relative to each other to perform the required optical stretch so can be the same angle from what I have seen so far. The problem at hand is trying to find what glass materials will equate to the liquids they are substituting.
Glass, Arsenic Trisulfide 2.04
Glass, Crown (common) 1.52
Glass, Flint, 29% lead 1.569
Glass, Flint, 55% lead 1.669
Glass, Flint, 71% lead 1.805
Glass, Fused Silica 1.459
Glass, Pyrex 1.474 [this is interesting]
Lucite 1.495
Nylon 1.53
Obsidian 1.50
Plastic 1.460 - 1.55
Plexiglas 1.488
Nothing at 1.3 though...
BK7 seems to have an Ri around 1.5, but I did find values higher than that listed...
Mark
If we go back to the original liquid filled DIY lenses from 2002, you might remember that they were filled with Water (in 1 prism @ 30 degrees) and Turpentine Oil (in the second prism @ 24 degrees).
Their refractive indexes are as follows-
Water (20° C) 1.33283
Turpentine 1.472 [there is no listing for Turpentine oil, but common household terps is oil based anyway]
I've dismissed the theory for the need for varying prisms angles as by default, the angles for the HE lens are positioned relative to each other to perform the required optical stretch so can be the same angle from what I have seen so far. The problem at hand is trying to find what glass materials will equate to the liquids they are substituting.
Glass, Arsenic Trisulfide 2.04
Glass, Crown (common) 1.52
Glass, Flint, 29% lead 1.569
Glass, Flint, 55% lead 1.669
Glass, Flint, 71% lead 1.805
Glass, Fused Silica 1.459
Glass, Pyrex 1.474 [this is interesting]
Lucite 1.495
Nylon 1.53
Obsidian 1.50
Plastic 1.460 - 1.55
Plexiglas 1.488
Nothing at 1.3 though...
BK7 seems to have an Ri around 1.5, but I did find values higher than that listed...
Mark
It was over 160 pages this morning. This alarms me a bit - not knowing what useful stuff they have removed...
Mark
Mark
Price Increase?
I ordered J25 5X7 wedges/prisms this morning and they were $49 (not $39) as mentioned before. It was the same lady Ms Suzanne. Has anyone else recd the older price?
I ordered J25 5X7 wedges/prisms this morning and they were $49 (not $39) as mentioned before. It was the same lady Ms Suzanne. Has anyone else recd the older price?
Yea, I still have some refelction in the image ( if there is a darker scene with some light patches in it, that gets reflected on the Left quarter of the image.
I haven't actually cleaned the lenses nor moved them since I put them up for testing :-/ (over 8 months ago now) hahaha, they are filthy with fingerprints & sawdust... I should get them down and do some adjustments, but I'm happy atm with the 2 prisms, and I'm sure I can adjust them better for less reflection (maybe a splitter/mask in between the 2 prisms?... )
ie like this, you can see the rectangular masking in front of the prism.
<-- projected image
<-- Projector
or:
<-- projected image
<-- Projector
I haven't actually cleaned the lenses nor moved them since I put them up for testing :-/ (over 8 months ago now) hahaha, they are filthy with fingerprints & sawdust... I should get them down and do some adjustments, but I'm happy atm with the 2 prisms, and I'm sure I can adjust them better for less reflection (maybe a splitter/mask in between the 2 prisms?... )
ie like this, you can see the rectangular masking in front of the prism.
<-- projected image
<-- Projectoror:
<-- projected image
<-- Projector
Steve,
I think the mask needs to go on the rear face of the prisms closest to the projector...
Mark
I think the mask needs to go on the rear face of the prisms closest to the projector...
Mark
yes, but you will still get a reflection from the image going through the first prism, (entering prism face & exiting prism face) - mainly stopping the 'entering 1st prism face reflection?)...
dunno, I might try one anyway, when I get the time.
dunno, I might try one anyway, when I get the time.
I had many successful runs with those Evright prisms and no reflections, but IMHO, you can not beat a set of AR coated prisms. The card is best at the source of the light - the projector...
Mark
Mark
Roar, thanks for the hospitality the other night. it was great to see your set up and take that extra set of prisms off your hands. can't wait to apply them in my setting soon. you gave me a lot of info to crunch.
Question??? I was looking at purchasing the Epson Powerlite Home 1080p projector. right now it is the frontrunner. Pricing and performance fits my bill. HOWEVER, upon further review it does not do Vertical Stretch? or am I missing something on its specs? and if it does not offer VS do I have any other options with this PJ or am I just going back on the market looking for another PJ that offers VS through the HDMI? (and offers the throw etc... that I need)...
Any and all help appreciated. would like to stay with the Epson if i could.
PS. not interested in adding a scaler into the mix... (again, more $$$)
Rotten...
Question??? I was looking at purchasing the Epson Powerlite Home 1080p projector. right now it is the frontrunner. Pricing and performance fits my bill. HOWEVER, upon further review it does not do Vertical Stretch? or am I missing something on its specs? and if it does not offer VS do I have any other options with this PJ or am I just going back on the market looking for another PJ that offers VS through the HDMI? (and offers the throw etc... that I need)...
Any and all help appreciated. would like to stay with the Epson if i could.
PS. not interested in adding a scaler into the mix... (again, more $$$)
Rotten...
ROTTEN ROD said:
This projector will work with SD sources, but locks up for HD or upscaled SD.
A external VP or HTPC is the only option with this unit over HDMI apart from the Samsung HD 950 (960) which has EZVIEW that provides both Vertical Stretch and Horizontal Squeeze...
Mark
stevodude said:
<-- projected image
or:
<-- projected image
Hey Steve, the prisms alignment that you have will form a Horizontal Compression lens, not expanding one as you need the front prisms thick end towards the screen and the apex of the rear prism towards the projector...
Mark
ah yea, back to front :-/ ment to be the other way round, just did a quick mock up one busy mornin...
projector is bein borrowed atm, so can't really do any tests with masks, and also too busy with new baby & building some single driver speakers for the 'wife's tv area'.
projector is bein borrowed atm, so can't really do any tests with masks, and also too busy with new baby & building some single driver speakers for the 'wife's tv area'.
Just thought I would share some pictures of my housing for the prisms. It has been a long while since I have been able to sit down and do this, but I think I got things together correctly. Haven't actually sat down in front of a projector yet, but that will happen soon. Hopefully, my calculations are correct...
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Well, it is certainly crude, and the pictures actually look a lot more sloppy than it looks in real life (not sure why--perhaps because it is so up close, and the image really shows the difference in browns between the tape and the housing itself.
But the idea was more "proof of concept" than anything else, especially in light of the fact that the basket that I used cost a mere $7.50 at the local Hobby Lobby store. With other materials, I would say the total cost of the housing is $15, and the prisms cost about $60 total. Unfortunately, these aren't AR-coated, but perhaps that is next. We'll see how these go.
The only thing I am really concerned about is the adhesive failing where the elevator bolts are adhered to the prisms. So at least in the front prism, I also adhered a strip of wood cut in the shape of the prism over the elevator bolt. It has no load right now, unless the elevator bolt fails, in which case I would hope that it holds the prism in place for me to remove the housing from the ceiling before the prism falls on someone!
But the idea was more "proof of concept" than anything else, especially in light of the fact that the basket that I used cost a mere $7.50 at the local Hobby Lobby store. With other materials, I would say the total cost of the housing is $15, and the prisms cost about $60 total. Unfortunately, these aren't AR-coated, but perhaps that is next. We'll see how these go.
The only thing I am really concerned about is the adhesive failing where the elevator bolts are adhered to the prisms. So at least in the front prism, I also adhered a strip of wood cut in the shape of the prism over the elevator bolt. It has no load right now, unless the elevator bolt fails, in which case I would hope that it holds the prism in place for me to remove the housing from the ceiling before the prism falls on someone!