Dual Focal Length Response
I was in a moto crash recently, and the insurance check was issued today, so I think that I can definitely afford the dual focal length (shorter rear focal length) fresnel design if there is enough demand for it.
The lenses will DEFINITELY be offered split. That is what most people prefer, and also it is actually a bit cheaper to order them unglued in the first place! You can easily glue them back together with just about any adhesive around the edges if you prefer a single-lens design.
If I receive enough emails or posts here today and tomorrow, I will probably start offering the new design upgrade on my website for about $50 later tonight or tomorrow (April 6th). Does that sound good to everyone? (you could still order the original $30 single FL lens if you prefer).
I was in a moto crash recently, and the insurance check was issued today, so I think that I can definitely afford the dual focal length (shorter rear focal length) fresnel design if there is enough demand for it.
The lenses will DEFINITELY be offered split. That is what most people prefer, and also it is actually a bit cheaper to order them unglued in the first place! You can easily glue them back together with just about any adhesive around the edges if you prefer a single-lens design.
If I receive enough emails or posts here today and tomorrow, I will probably start offering the new design upgrade on my website for about $50 later tonight or tomorrow (April 6th). Does that sound good to everyone? (you could still order the original $30 single FL lens if you prefer).
I disagree on that as ive tried a frensels that have the same rear focal on both except one had a longer focal on top then the rear and the other had the same as the rear, both wer the same distance from the light source, the frensel that had the 2 different focals was the brighter frensel.
About the transmisibility, i had my frensels custom made with super high grade optical acrylic, they are 96% transmisive and arent cheap at all to buy due to the higher transmisive performance, and are about the most transmisive you can get a frensel lens, an ohp frensel lens is typical of 92% transmisive and down hence their price. Im not knocking your frensels, but for thier price, i doubt they are even 92% transmisive, for a frensel of that size to buy in a single lens at a 96% transmisive, they are over $60 each in a bulk buy and just for the 1 lens direct from the manufacturer before taxes, non custom made, and from china.
Trev
Trev,
Thanks for the input. Even if ther is something to having different focal lengths, using a shorter rear focal length will have a terrific affect on improving light collection. I think we had originally calculated that a 8.9" rear FL lens would collect 250% as much light as a 13" rear FL, but I don't remeber exactly what it was.
Our manufacturer has confirmed that the new fresnel lenses are from 92% transmisity acrylic, so it's interesting that you mentioned 92% - that must be an industry standard I guess. Whether mine are 92% vs. 98% shouldn't matter too much ... 6% is definitely tolerable since 6% of 500 lumens output is only 30 lumens difference, though I agree you got some mighty special lenses. Nevertheless, I think that to most people our new setup should be a hit, especially for ~$50!!
Thanks for the input. Even if ther is something to having different focal lengths, using a shorter rear focal length will have a terrific affect on improving light collection. I think we had originally calculated that a 8.9" rear FL lens would collect 250% as much light as a 13" rear FL, but I don't remeber exactly what it was.
Our manufacturer has confirmed that the new fresnel lenses are from 92% transmisity acrylic, so it's interesting that you mentioned 92% - that must be an industry standard I guess. Whether mine are 92% vs. 98% shouldn't matter too much ... 6% is definitely tolerable since 6% of 500 lumens output is only 30 lumens difference, though I agree you got some mighty special lenses. Nevertheless, I think that to most people our new setup should be a hit, especially for ~$50!!
Considering I want to use a 400 W MH, I don't think I'll see the difference between 92% and 96 or 98.
If I were using a 150W or 250W bulb, I might be a little more concerned.
If I were using a 150W or 250W bulb, I might be a little more concerned.
In the sketch you posted you have the corners cut. I can see the surface area is still the full size you mentioned... but why have the lens designed with cut corners?
JCB
www.diybuildergroup.com
JCB
www.diybuildergroup.com
4% may not sound alot, but trust me, even with a 400w bulb you will see the difference, i see the difference by just looking at the lens in my hand, its like looking at a hazed glass compared to a clear glass, thats the difference. Even though its only 4% more transmisive, the intensity is way upthere, all of the colours are much more viabrant and the image is brighter. With the 92%, the colour of white also looks dirty where as the 96% looks a clean bright white, so it also impacts the colour.
Its also 4% of light less in your optics that we cant aford to loose with an lcd setup, thats 800lm of raw light lost from a 400w bulb just with the frensel alone, then lets not forget the lcd will pass only about 10%, then in each lens in the triplet there will be roughly a 2- 4% loss, a rough 2 - 4% in the condenser and better yet a 25%+ loss from the light with a spherical reflector, without a shperical reflector that figure would be atleast 50%, so the losses add up, and you truly do see the difference.
Ive got a frensel lens here thats 92% and after using the 96% i wouldnt go back to using a 92% transmisive frensel again.
Allan regarding the industry standard, you have hit it on the head, its price vs quality.
Trev
Its also 4% of light less in your optics that we cant aford to loose with an lcd setup, thats 800lm of raw light lost from a 400w bulb just with the frensel alone, then lets not forget the lcd will pass only about 10%, then in each lens in the triplet there will be roughly a 2- 4% loss, a rough 2 - 4% in the condenser and better yet a 25%+ loss from the light with a spherical reflector, without a shperical reflector that figure would be atleast 50%, so the losses add up, and you truly do see the difference.
Ive got a frensel lens here thats 92% and after using the 96% i wouldnt go back to using a 92% transmisive frensel again.
Allan regarding the industry standard, you have hit it on the head, its price vs quality.
Trev
jcbklyny said:
That sketch also does not add up, the border is .5" - the whole size is 15.5" and the usable area is 15" ... just think about it.
ace3000_1 said:
Another factor is heat. That 4% light isn't just disappearing it's going straight into the plastic as heat energy (mostly). Not a big factor.
Personally, I haven't seen the difference. But this is a DIY project for me, not a buy the best and get the best - if you're just gonna buy the best, go pick up a HD Projector. To me DIY is about finding price to perfomance for each person's liking. That said, the DIY community should be about testing different products so each person can decide what that optimanl price😛erformace point for themselves is without testing each and every thing.
So I have a question for ace, since you mention LCD, reflector, condensor, fresnel, and triplet as sources of light loss, given say $50, which one would you improve first (given that you started with all of them overhead crappiness)? Which would you think would give the better performance.
I'm really curious, because I know you've done so much testing with different optics etc. And like you said, 4% doesn't tell the full story.
Certainly 14.5" square makes more sense with that diagram lol.
As far as price perf ratio goes for me, I'd rather initially spend more money on a quality LCD than quality optics because, after all, you can't polish a turd. However, if I buy a high end LCD and so-so optics, my upgrade path is much easier considering the lesser initial investment. I'd rather scrap $50 optics to get more expensive ones than scrap a $200 lcd to buy a $450 one.
That's just my opinion...
As far as price perf ratio goes for me, I'd rather initially spend more money on a quality LCD than quality optics because, after all, you can't polish a turd. However, if I buy a high end LCD and so-so optics, my upgrade path is much easier considering the lesser initial investment. I'd rather scrap $50 optics to get more expensive ones than scrap a $200 lcd to buy a $450 one.
That's just my opinion...
Hmm that depends how technical you want to go, but if i had a full set up, id be making sure i had a REAL spherical reflector and not a soup laddel ( no pun intended allan at all, just a good example) for starters, i always start right back at the source, if the source is crap, why bother with the rest?
After we have a good bright source light, id be looking at a decent reflector, probally the best investment money can buy regarding projectors, is a decent reflector, without one, its like using a whole box of matches to light 1 cigarete, its ineficient and a waste. So what we want to do is get the most of that light into our condenser and through the rest of the system, ( reflectors arent exspensive btw, i sell them for $15, they are precision and made for a 250w hqi source). So with a soup laddel, id say you would be getting a max of 40-50% of your light, without a any reflector half that. With a proper shperical reflector you will utilise anywhere from 50% upto 65% of your light, now if we want to spend more money then go for an eliptical reflector, we can gain another 30% of light if not more on top of thos figures.
Now we have the condenser, normal glass condensers hardend or not will reflect a certain degree of light, this also includes optical grade glass. The condensers i use have a anti glare coating that eliminates the reflected light going back to its source, this actually helps to get more light through the condenser and into the system, once again $15. I have also seen a big difference with and without the coating on the exact same spec condenser.
Now, we have the frensel, if you realy want an optimal frensel then get one thats anti glare ( as they reflect light just like the condenser above), they are available but very pricey out of our reach, so the next best thing is to find the clearest frensel we can find, the light thats reflected back to the source we can recycle with a pyramid thats calculated at the correct angle to reflect the light back at paralelle, (this makes a big diff btw). So if we have a 96% transmisive frensel, and a light recycler, then our frensel may gain a 2% increse of light in our light engine as that light that is reflected back, is somwhat being used hence recycled.
Lcd, well they all vary i wont get into that.
Mirror, just like the frensel and condenser it will reflect light, except with a mirror we want to reflect (reflectance)as much light as possible through our projection lens, the lowest spec id ever use for a mirror is 96% as once again we are loosing a 4% loss of light. The higher the reflectance, the better for a mirror, 98% is about the highest you will find in our price range unless you own GM.
Now we have the projection lens, a triplet will always use more light then a doublet of the same spec, but one thing is the doublet is crap, the triplet is the only decent projection lens to use for a decent projection. Now depending on what kind of money you have will depend on the quality of the lens, this will include the feild of veiw, the power, the coating on the optics and the grade of glass. Ever wonderd why a pro projector has coatings on its projection lens? why thats so there is less glare off of each lens in the triplet so more light can go through the actuall lens making it more eficient, and to cause less aberations, distortion ect. The diylabs triplet doesnt have any coating, and i can garentee you that if it was coated, you would see a big diff, but then we are talking money.
So to round it up, if you have a decent reflector, a decent condenser, a decent frensel, a light recycler, and a good reflectance front surface mirror, then we can aford to run a cheap triplet with the extra light loss compared to doublet, but yet have a supurb image at or even brighter then the doublet as we have made our light engine as efficient as possible. Without taking care of the light engine and just changing a doublet with a triplet, you will just loose light. If we want to go even further and spend a wad of cash, then get a ar coated triplet to match the light engine, and i can garentee you that a 250w hqi, setup in the right way with decent optics, will come close to a 400w setup with crap optics if not surpass. If you later upgraded to a 400w bulb like crusers from the 250w for that extra oomf, and set the light engine up right, whoa be prepared to go blind.
You know Mr KH, i see so manny setups in here where people think a 250w isnt bright enough or are disapointed, it truly amazes me. Why is this? its simply because they havnt spent enough time, enough hands on experience to get the optics lined up right, (also a little research doesnt go astray), and all it takes is a center line, clear optics and abit more time. So it not only comes down to what we pay for, but also what we put into it.
I hope somone can learn from this, its a ******** long post lol
Trev
But why have a good lcd if your going to run it through crap optics in the first place? thats creating a turd lol
Trev
Why have great optics for a crappy lcd? My point is upgrading cheap optics is more cost effective than upgrading an lcd, especially since optics can be upgraded a piece at a time, whenever u can afford it. Not everyone can afford to blow all that money on the absolute best optics AND a nice LCD. I personally see ANY 7" LCD as a compromise in quality, so use all the great optics you want, that thing will never give a sharp enough picture to impress me at a very large size.
I'm sorry Trev I'm not tryin to dis you cause you know a hell of a lot about this stuff. It just seems silly to me that you argue so seriously about having the best optics available, while using a 720*480 7" screen that is certainly not the best in the lcd department. Sure it's a nice little screen and it makes for a small projector, but I bet if you'd spent all that time, money, and research working on a pj with a high res LCD like Cruser's, then your results would really be worth all these high end optics.
of course that's just my opinion
I'm sorry Trev I'm not tryin to dis you cause you know a hell of a lot about this stuff. It just seems silly to me that you argue so seriously about having the best optics available, while using a 720*480 7" screen that is certainly not the best in the lcd department. Sure it's a nice little screen and it makes for a small projector, but I bet if you'd spent all that time, money, and research working on a pj with a high res LCD like Cruser's, then your results would really be worth all these high end optics.
of course that's just my opinion
Why buy optics if you only plan to replace them? That seems like a waste of money to me.
Anyway the 800x480 7" screen gives a perfectly clear picture for me, you have to see it in person, because as always pictures don't do it justice. It also means you can make a very small pj. But, as you say, that is your opinion, not mine.
Anyway the 800x480 7" screen gives a perfectly clear picture for me, you have to see it in person, because as always pictures don't do it justice. It also means you can make a very small pj. But, as you say, that is your opinion, not mine.
OK OK hold it!
I don't want a big off topic thing going on here, there are different approaches, and that's my whole point. (we don't need to discuss them)
Ace's info is.... Awesome. (Thanks ace!)
I was asking specifically in regards to light emissivity, not quality or size which have been brought up, there's nothing wrong with that - but in a thread about a fresnel it seems kinda out of place. I guess I kinda opened the door for all of this, I just wanted Ace's opinion of how high on "the list" he thinks a fresnel lens is in comparison to other optics.
Re: How much you put in, I totally agree - a little effort and sometimes brain work(hopefully not required though) can go a long way.
I don't want a big off topic thing going on here, there are different approaches, and that's my whole point. (we don't need to discuss them)
Ace's info is.... Awesome. (Thanks ace!)
I was asking specifically in regards to light emissivity, not quality or size which have been brought up, there's nothing wrong with that - but in a thread about a fresnel it seems kinda out of place. I guess I kinda opened the door for all of this, I just wanted Ace's opinion of how high on "the list" he thinks a fresnel lens is in comparison to other optics.
Re: How much you put in, I totally agree - a little effort and sometimes brain work(hopefully not required though) can go a long way.
I'm done with this discussion here. This thread is so ALan can sell his large fresnels, and should get back to that point.
I was merely trying to defend mid range optics as a viable solution for those of us who want to use a 17" screen, but can't afford to break the bank on $200 custom fresnels as Cruser did.
I was merely trying to defend mid range optics as a viable solution for those of us who want to use a 17" screen, but can't afford to break the bank on $200 custom fresnels as Cruser did.
Sounds to me like 92% transmissive and dual focal lengths is gonna be a good option for most people for around $50. If you want to spend $200+ on a fresnel and other top end components that will give you a few % more light its prolly gonna add up to cost more than something like an Infocus X1 or other commercial projector, so you may as well buy one of those anyway and have done with it.
Mr.Kh said:
I messed up the drawing! It is supposed to be an additional 0.25" on each edge. The largest square is still 15"x15", but they had to add a 0.5" long corner cut so that they wouldn't crack during shipping, so I had them make the lens just a bit bigger so that the corners wouldn't eat up the 15x15 square that I was going for. I'll change the diagram tonight.
As for the haziness Trev was talking about, I think that is focal length issues - different lenses (usually with differing focal lengths - use different techniques for the shape of each groove - they are not all oriented the same way. For example, our current 13" FL lens half appears much more transparent than our 8.9" FL lens half, but they both still have the same transmisity. Lenses bend light, especially fresnel lenses, so you can't think of them as you can a piece of glass or sheet of plain acrylic when determining transmisity. Bottom line - you're gonna get the same naked-eye brightness with the new 15" lens as you would with any other high quality 8.9" rear FL lens - you can tar and feather me if I'm wrong 🙂 Or maybe put me on a rotissery (mmmm - barbeque)
Faith, ive got more lenses here then you can imagine, ive tried out different triplets, condensers, reflectors you name it, there is no race on who has the best image, but i will say this, the reso of a lcd has nothing at all to do with how sharp an image is, that is coverd by the optics.
If you had a 7inch lilliput i can garentee you that there is no disapointment at all, its actually clearer then a xga monitor before being blown up.
The way i see it, why buy crap optics in the first place if your only going to upgrade them?, thats spending 2x the money, i tend to do the job right the first time, and im not arguing at all in here, im just stating facts.
Trev
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