Ahhh yes, thats right, I was actually going to do that (cut a notch & bend the L channel), but completly forgot about it when I actually got the bits, and ended up riveting it together in a square frame... Doh!
Might have to make a rev 2 prism frame.
I only put a bolt on the bottom because the whole thing is stable with just an M6 bolt through a 3mm sheet of aluminium rivited across the base of the frame (allows the bolt clearance between the aluminium channeland the plastic adjusters for getting the glass perfectly horizontal.
On a slight tangent, preceedings will slow for awhile due to helping my wife yesterday delivering this:
link doesn't seem to be working, but hopefully you can see the thumbnail... 🙂 not the thumb nails, they are tiny. 😀 😀 😀 😀
Brooke was born yesterday the 2nd of Jan, weighing in at a regular bundel of 3.46kg and 51cm in length, all circuits functioning perfectly, especially the amplification section
😀 😀
Might have to make a rev 2 prism frame.
I only put a bolt on the bottom because the whole thing is stable with just an M6 bolt through a 3mm sheet of aluminium rivited across the base of the frame (allows the bolt clearance between the aluminium channeland the plastic adjusters for getting the glass perfectly horizontal.
On a slight tangent, preceedings will slow for awhile due to helping my wife yesterday delivering this:
An externally hosted image should be here but it was not working when we last tested it.
link doesn't seem to be working, but hopefully you can see the thumbnail... 🙂 not the thumb nails, they are tiny. 😀 😀 😀 😀
Brooke was born yesterday the 2nd of Jan, weighing in at a regular bundel of 3.46kg and 51cm in length, all circuits functioning perfectly, especially the amplification section
😀 😀
Congrads Steve, what a way to start a new year 😀
Better not let my GF see this now as she wants one so bad...
Mark
Better not let my GF see this now as she wants one so bad...
Mark
Steve: Great news, and congratulations. Looks like you got a good 2007 model! I am thinking of upgrading myself, after my 2005 model just tried to gouge my eyes out after not letting her up on the sofa the other day. I have a scratch on my face to prove it. The 2002 and 2003 models I have don't seem to have this flaw in their programming...
Well back on topic.
I did another prisms re-alignemnt tonight. I have found that there is such a fine line between the "right amount" of stretch and too much that causes reflections...
Geometry is very good and CA is fairly even on both sides. There is a very small reflection on the hard left, none on the right. If you go that little bit too far, a nice rainbow is seen in the centre as well, so it is a balance to find the right amount...
Mark
I did another prisms re-alignemnt tonight. I have found that there is such a fine line between the "right amount" of stretch and too much that causes reflections...
Geometry is very good and CA is fairly even on both sides. There is a very small reflection on the hard left, none on the right. If you go that little bit too far, a nice rainbow is seen in the centre as well, so it is a balance to find the right amount...
Mark
Mark Techer said:
Hey Mark, did you use a grid pattern to align the image or just eye ball it? Thinking I should do this too.
Bud
BTW, Happy New Year!
Mark, when you say "re-align", are you talking about just rotating the prisms, or are you also moving the prisms to the left and right at all?
I seem to have more CA on the left side of the screen compared to the right. I think this can be made more uniform by shifting the prisms left and right relative to each other. I'm guessing that the distance the beam travels through the first prism needs to be the same in the second prism to cancel out the rainbow produced by the first prism.
Unfortunately, moving the prisms left/right is the one adjustment that I didn't include in my enclosure design.
But right now I'm hardly seeing any reflections at all, so I'm less willing to dismount the lens and realign it. Even though I can see the CA on a grid test, I honestly can't see it when watching a movie and find reflections more annoying than CA. Which is the main reason I have stayed with a 2-prism setup.
I seem to have more CA on the left side of the screen compared to the right. I think this can be made more uniform by shifting the prisms left and right relative to each other. I'm guessing that the distance the beam travels through the first prism needs to be the same in the second prism to cancel out the rainbow produced by the first prism.
Unfortunately, moving the prisms left/right is the one adjustment that I didn't include in my enclosure design.
But right now I'm hardly seeing any reflections at all, so I'm less willing to dismount the lens and realign it. Even though I can see the CA on a grid test, I honestly can't see it when watching a movie and find reflections more annoying than CA. Which is the main reason I have stayed with a 2-prism setup.
Bud Bray said:
Same back at ya 🙂
I have stopped using test patterns simply becuase you tend to be too critical with them. I generally align the prisms by having the same amount of stretch at each end. This is a bit hard for me right now as my screen is still 235, not 237, so I have a slight lightspill on the sides that I have to get as symmetrical as possible...
MikeP said:
I did have way more CA on the right hand side, but managed to correct most of that last night. The right still has the worst pincushion though, and tilting the entire lens does not seem to correct this. I do believe I need to tilt the rear prism only to correct this.
Like you, my prisms only just fit into the case, so the only option I have for lateral shift is to move the entire lens left or right...
Corner to corner focus was very good last night though 🙂
Mark
hahah yea thanks, managed to whip up a mkII frame for the socnd prism.
Utelizing the notch and bend method...
Black thing is a 4mm think high density rubber for the prisms to sit on.
Initial cut out ready for bending
Cut/bent and pop-riveted, rubber cut to size.
cut out and bent and pop-riveted, and rubber in place
just have to make the bottom & the bolt position.
easier to make as 1 piece actually, than 4 pieces 🙂
Utelizing the notch and bend method...
Black thing is a 4mm think high density rubber for the prisms to sit on.
Initial cut out ready for bending
An externally hosted image should be here but it was not working when we last tested it.
Cut/bent and pop-riveted, rubber cut to size.
An externally hosted image should be here but it was not working when we last tested it.
cut out and bent and pop-riveted, and rubber in place
An externally hosted image should be here but it was not working when we last tested it.
just have to make the bottom & the bolt position.
easier to make as 1 piece actually, than 4 pieces 🙂
Hello all,
I just finished watching another movie with my 4 prism setup (had several dark scenes with bright lights), and the reflections were quite a bit more apparent than with other movies. Don't get me wrong, I still think the DIY prisms are wonderful, but I've caught this disease that won't let me stop trying to reduce all the little left-over optical problems.
I really like the 4 prisms because I get a lot less CA than when I tried two, but I understand now how some of you prefer to use just 2 because of the reduction in reflections.
But this got me to thinking, I don't think it would be too hard to eliminate half the reflections from the 4 prism setup so that it would behave similar to 2 prisms. Here are my thoughts...
The way I have the 4 prisms currently arranged is really like a set of 2 prisms. In other words, all the prisms are about 8 degrees each, but the first two are almost touching so they "look" like a 16 degree prism, and the same goes for the second set of prisms. I think it would be great if we could find cheap prisms with large angles (say 15 to 25 degrees) because then I don't think we would need to use four of them, but beggers can't be choosers. In any case, it has been suggested before that the only way to get rid of the reflections between two adjacent prisms is to put a layer of something between the two that has the same refractive index. I think that this is doable.
One possibility would be to create a small sealed cavity between two adjacent prisms, then fill the cavity with something that has a refractive index of about 1.5 (maybe mineral oil or glycerine). Water could even be used to try out the theory since it has an index of about 1.33 so it would eliminate most of the reflections.
Another possibility (but might be riskier) is to buy an optical cement that has a refractive index of 1.5 and use this to "glue" two prisms together. Some of these cements cure with ultraviolet light (same wavelength as a cheap blacklight), so this allows you to position the two glass pieces before using the UV light to cure the cement. It might even be possible to set them out in the sun and let the UV from the sun cure the cement over a longer period of time, but I'm not sure how well that would work. One downside is that I think it might be very hard to do this without getting bubbles between the two pieces of glass, and I have also read that "stray" UV light can cause the cement to cure early, so this could be tricky.
Here's one company I found that sells optical cements:
http://optical-cement.com/summers/optical/cements/
I'm currently using two J24 (small) prisms and two J26 (large) prisms. The J26's are HUGE, and much bigger and heavier than I think is practical for a final solution. Last time I checked (this past Wendesday), the J25 prisms were still unfortunately on backorder from massillonplaque.com, but since the J26 prisms are unwieldy, I've gone ahead and ordered some J25 prisms anyway...I just hope they'll be available soon.
Ed
I just finished watching another movie with my 4 prism setup (had several dark scenes with bright lights), and the reflections were quite a bit more apparent than with other movies. Don't get me wrong, I still think the DIY prisms are wonderful, but I've caught this disease that won't let me stop trying to reduce all the little left-over optical problems.
I really like the 4 prisms because I get a lot less CA than when I tried two, but I understand now how some of you prefer to use just 2 because of the reduction in reflections.
But this got me to thinking, I don't think it would be too hard to eliminate half the reflections from the 4 prism setup so that it would behave similar to 2 prisms. Here are my thoughts...
The way I have the 4 prisms currently arranged is really like a set of 2 prisms. In other words, all the prisms are about 8 degrees each, but the first two are almost touching so they "look" like a 16 degree prism, and the same goes for the second set of prisms. I think it would be great if we could find cheap prisms with large angles (say 15 to 25 degrees) because then I don't think we would need to use four of them, but beggers can't be choosers. In any case, it has been suggested before that the only way to get rid of the reflections between two adjacent prisms is to put a layer of something between the two that has the same refractive index. I think that this is doable.
One possibility would be to create a small sealed cavity between two adjacent prisms, then fill the cavity with something that has a refractive index of about 1.5 (maybe mineral oil or glycerine). Water could even be used to try out the theory since it has an index of about 1.33 so it would eliminate most of the reflections.
Another possibility (but might be riskier) is to buy an optical cement that has a refractive index of 1.5 and use this to "glue" two prisms together. Some of these cements cure with ultraviolet light (same wavelength as a cheap blacklight), so this allows you to position the two glass pieces before using the UV light to cure the cement. It might even be possible to set them out in the sun and let the UV from the sun cure the cement over a longer period of time, but I'm not sure how well that would work. One downside is that I think it might be very hard to do this without getting bubbles between the two pieces of glass, and I have also read that "stray" UV light can cause the cement to cure early, so this could be tricky.
Here's one company I found that sells optical cements:
http://optical-cement.com/summers/optical/cements/
I'm currently using two J24 (small) prisms and two J26 (large) prisms. The J26's are HUGE, and much bigger and heavier than I think is practical for a final solution. Last time I checked (this past Wendesday), the J25 prisms were still unfortunately on backorder from massillonplaque.com, but since the J26 prisms are unwieldy, I've gone ahead and ordered some J25 prisms anyway...I just hope they'll be available soon.
Ed
stevodude said:
Steve,
First off big congrats on your new family member... yeah you'll lose some sleep, but it's worth the tradeoff.
Next is just a quick question about your prism mount. Are you using the rubber mainly to protect and cushion the prisms, or are you using it to block reflections (or both?)
Ed
ejbod said:
Yes, I too prefer the 4 prism set...I find the picture is better(to my old eyes anyway). I'm thinking that we really need to get them anti-reflective coated somehow. Probably once i'm back to work(off on seasonal layoff now) and making some $$$ again...i'll go for the coatings posted earlier in this forum. Even at$40/prism, it's still cheaper that a prismasonic/panamorph setup! Till then, i'll put up with the occasional reflection and enjoy my CIH theatre.
The prisms that we have in Australia are 14 degrees. The two prisms lens is good, but still produces some CA which can be made symmetrical with propper alignment...
We can also get the 8 degree prisms as well...
Mark
We can also get the 8 degree prisms as well...
Mark
OK I have prisms setup as a temporary test, and so far looks pretty good.
have slight color separation on the RH side now instead of the left, but thats OK, in windows the desktop is a little fuzzy, but that is to be expected.
but watching a movie it's all good! 😀 😀 😀
go the jump here to see photo's
next up is I'm going to make a sheet metal bender today & make an aluminium box ( I want aluminium because the prisms are heavy enough as it is 🙂 ), and should easily be able to bend up a sheet of 2mm or 3mm aluminium. - can post picks of the sheet bender if ya's want ( will cost about $20 worth of parts, but nothing for me, as I have the steel sitting around) - will need a thick plate steel length probably 6mm+ thickness & 2 lengths of L channel Steel, probably around 4mm+ thickness, and 2 bolts & a length of steel rod 8mm+ for the handle. only bit of weilding if you want, as it can be bolted, is the handle to one of the lengths of L channel.
have slight color separation on the RH side now instead of the left, but thats OK, in windows the desktop is a little fuzzy, but that is to be expected.
but watching a movie it's all good! 😀 😀 😀
go the jump here to see photo's
next up is I'm going to make a sheet metal bender today & make an aluminium box ( I want aluminium because the prisms are heavy enough as it is 🙂 ), and should easily be able to bend up a sheet of 2mm or 3mm aluminium. - can post picks of the sheet bender if ya's want ( will cost about $20 worth of parts, but nothing for me, as I have the steel sitting around) - will need a thick plate steel length probably 6mm+ thickness & 2 lengths of L channel Steel, probably around 4mm+ thickness, and 2 bolts & a length of steel rod 8mm+ for the handle. only bit of weilding if you want, as it can be bolted, is the handle to one of the lengths of L channel.
VERY nice job! Can't wait to see the finished product...might give Mark a run for his money! *grin*
Bud
Bud
Mark Techer said:
I'm jealous... 14 degree prisms would be nice. My 4 prism setup with 8 degree prisms produces CA, too, but it's noticeably less than just two prisms and could be close to what you get with two of your prisms. I've also noticed what you mentioned about alignment. It takes a bit of tweaking, but I can eventually get the CA symmetrical on both sides.
Ed
Mark Techer said:
Yeah, I'm jealous too. I might try to find a U.S. vendor for prisms with a larger angle. I'm pretty happy with just the 8-degree prisms and I can imagine that with 14-deg prisms I'd never even consider the 4-prism setup.
But now I see what happens when you finally get these things mounted in an enclosure. Now that my enclosure is mounted, it's hard to get excited about taking it down to mess with it or re-align it. I'd rather watch movies now 😎
My camera arrived and I've taken some pictures of my enclosure. Hope to have them posted to a website with a description of the construction details soon.
OK, I have *finally* found the time to write up my entire Anamorphic Lens construction project. You can find it at http://www.zuggsoft.com/theater/prism.htm
It includes some introduction material, similar to what Mark has in his blog. I've actually used the exact same scene from Star Wars, but my pictures are using my camera, projector and lens, not Mark's 🙂
I also describe the full construction of the enclosure and ceiling bracket. Here is a sample picture:
I also have a full Performance section where I discuss the aspect ratio uniformity, chromatic aberration, and reflections. There are some grid pictures that really show the chromatic aberration up close and personal.
Thanks again to everyone who has posted their ideas and results to this forum. I couldn't have built this without you! I hope my documentation on this will help inspire others to join the CIH club.
Feel free to post any comments or suggestions about my documentation.
It includes some introduction material, similar to what Mark has in his blog. I've actually used the exact same scene from Star Wars, but my pictures are using my camera, projector and lens, not Mark's 🙂
I also describe the full construction of the enclosure and ceiling bracket. Here is a sample picture:
I also have a full Performance section where I discuss the aspect ratio uniformity, chromatic aberration, and reflections. There are some grid pictures that really show the chromatic aberration up close and personal.
Thanks again to everyone who has posted their ideas and results to this forum. I couldn't have built this without you! I hope my documentation on this will help inspire others to join the CIH club.
Feel free to post any comments or suggestions about my documentation.
MikeP said:OK, I have *finally* found the time to write up my entire Anamorphic Lens construction project. You can find it at http://www.zuggsoft.com/theater/prism.htm
It includes some introduction material, similar to what Mark has in his blog. I've actually used the exact same scene from Star Wars, but my pictures are using my camera, projector and lens, not Mark's 🙂
I also describe the full construction of the enclosure and ceiling bracket. Here is a sample picture:
I also have a full Performance section where I discuss the aspect ratio uniformity, chromatic aberration, and reflections. There are some grid pictures that really show the chromatic aberration up close and personal.
Thanks again to everyone who has posted their ideas and results to this forum. I couldn't have built this without you! I hope my documentation on this will help inspire others to join the CIH club.
Feel free to post any comments or suggestions about my documentation.
VERY COOL
Mark
MikeP: Simply fantastic post and blog. You and Mark Techer have pretty much made the "bible" of DIY anamorphic lenses.
One thing I wanted to note--although right now it is untried (and am not sure if I am going to try it), there appears to be a fairly cheap solution for getting antireflective coatings on the prisms--reposted here:
By the way, the vikuiti films were a dud.
Anyway, I can appreciate that you might not want to include this info, especially since it is untried and unproven--but the option is there for people who might want to use it. And it still keeps the costs of DIY lenses significantly down compared to the pro lenses.
One thing I wanted to note--although right now it is untried (and am not sure if I am going to try it), there appears to be a fairly cheap solution for getting antireflective coatings on the prisms--reposted here:
By the way, the vikuiti films were a dud.
Anyway, I can appreciate that you might not want to include this info, especially since it is untried and unproven--but the option is there for people who might want to use it. And it still keeps the costs of DIY lenses significantly down compared to the pro lenses.
Sorry for the double post--but all this refining activity has gotten me to sit back down and really start hammering this thing out. I'll have some pictures to post later on, but it is a lot cruder than MikeP's, and is merely for proof of concept of some of these issues. I will most likely borrow MIkeP's way of sliding the lenses in and out, but in an interesting twist, I am trying to combine a VC lens (Panamorph P752) with the the HE DIY lens to get the proper 21:9 stretch from 4:3 source material, since I have a 4:3 projector and my goal is to utilize full panel with that projector (yes, I can achieve the full stretch with my projector)
My first thought was to increase the stretch of the DIY HE lens to its maximum to get the 21:9 stretch from 4:3, but I quickly realized that for the screen I have (DIY electric roll-up), I could not zoom the image in to make it small enough to fit on the screen anymore--everything was designed for my VC lens. But if I utilize full panel stretch, then expand it, then compress it, I should have no problem with fitting the image. THe question is--will the image be watchable with all of those prisms?
My first thought was to increase the stretch of the DIY HE lens to its maximum to get the 21:9 stretch from 4:3, but I quickly realized that for the screen I have (DIY electric roll-up), I could not zoom the image in to make it small enough to fit on the screen anymore--everything was designed for my VC lens. But if I utilize full panel stretch, then expand it, then compress it, I should have no problem with fitting the image. THe question is--will the image be watchable with all of those prisms?