330mm FL field fresnel with 290mm FL Triplet. Would that work together if I was to use it in a split fresnel configuration. How can you tell how much difference in FL between these 2 you can have at the most and least? Any responses most appreciated.
hi, you would need to place the bulb farther fron the rear fresnell.
A friend of mine has got a very good results with 330 field fresnell when 550 is recomended, just placing the bulb closer so it focuses light farther on the triplet like if he had larger fresnell.
your case is the oposite case. you need to place something farther. Good luck
A friend of mine has got a very good results with 330 field fresnell when 550 is recomended, just placing the bulb closer so it focuses light farther on the triplet like if he had larger fresnell.
your case is the oposite case. you need to place something farther. Good luck
You're right Rox. I'm building a PS1 projector with an unsplit 330mm FL fresnel and a 170mm FL copy lens. I don't want to spend more money for the 220mm FL so I made some tests and I found that with a distance of 620mm between the light source and the unsplited fresnels I manage to have the correct distance for my projection lens. In this test I replace de copy lens with a sheet of paper with a circle of the same diameter of my lens drawing in it, when I manage to have all the cone of light inside the circle then I place again my lens at the distance where the sheet of paper indicated.
Geetings
Rox said:
You wont get rings by changing the distances between the 2 frensels, but moving the light closer and farther from the rear frensels focal you will, you will also lose light. If your lucky you may just get flared corner edges.
Trev🙂
i mean to find the bulb position where most of light enters the projection lens.
Sorry but you mean you have only 1 x 330 fresnell? (don´t have 220 one and 330 one?)
Teorically any fresnell lens would do a good work, but do not go very far from its native focal if you want good results.
Generic 1/f=1/d1 + 1/d2
f=fresnell focal d1=bulb-fresnell dist d2=light condensed point (where projection lens should be placed)
Sorry but you mean you have only 1 x 330 fresnell? (don´t have 220 one and 330 one?)
Teorically any fresnell lens would do a good work, but do not go very far from its native focal if you want good results.
Generic 1/f=1/d1 + 1/d2
f=fresnell focal d1=bulb-fresnell dist d2=light condensed point (where projection lens should be placed)
sorry ace, i was asking to mengalva. I don´t understand him when he says he doesn´t want to spend mych more on 220 one.
I guess he has 220/330 unsplit
because he says he has good results placing the bulb at 620.
1/132 =1/620 + 1/d2 d2=167mm think would work with his lens.
(132mm is the conbined focal of 220/330)
I guess he has 220/330 unsplit
because he says he has good results placing the bulb at 620.
1/132 =1/620 + 1/d2 d2=167mm think would work with his lens.
(132mm is the conbined focal of 220/330)
Rox said:
Hi Rox,
I have two 330mm FL fresnels. In the begining of my project I took my fresnels from an 3M 2150 OHP and after cutting the fresnels I measure the FL of each one of the fresnels with the sunlight and found that both had the same FL. I also took the 330mm FL triplet from the ohp but in my initial test I found that with my thow distance (2.4 mts) the image was just 32" diagonal so I buy for US$6 a 170mm FL copy lens that gave me a 65" projected image. I know that the right fresnels for this lens must have between 180 FL and 220 FL but the total amount of the fresnel's price and shipping cost make me think about do some tests with what I had in my hands. I'm not a guru in optics topic, but I can tell you that I don't have rings in my projected image and the image is bright enough.
Greetings
so you mean that you are working with 62cm light placement from rear fresnell using 330/330 fresnells and you are having good results?
Very interesting 😀. I always thought that getting the lamp farther would work better than getting the lamp closer to the fresnell. In your setup, you doubled the distance from rear fresnell and still you are having good light. That sounds great.
The only problem i see is that you will have less light from the lamp hitting the fresnells. Thats because you are getting less solid angle from the lamp (the light cone is thiner). Thanks for your info 😀
Very interesting 😀. I always thought that getting the lamp farther would work better than getting the lamp closer to the fresnell. In your setup, you doubled the distance from rear fresnell and still you are having good light. That sounds great.
The only problem i see is that you will have less light from the lamp hitting the fresnells. Thats because you are getting less solid angle from the lamp (the light cone is thiner). Thanks for your info 😀
My current light setup is a CDM-T 150W with a cutted PAR30 as a reflector with 30 grades light beam, this is a mathias design
posts #1740 and #1756 of DIY Video Projector Part II
It gives me a decent picture but as you said I'm waisting a great amount of light so next weekend I'm going to buy a PAR20 with 10 grades light beam or less to capture the greater amount of possible light.
Greetings
posts #1740 and #1756 of DIY Video Projector Part II
It gives me a decent picture but as you said I'm waisting a great amount of light so next weekend I'm going to buy a PAR20 with 10 grades light beam or less to capture the greater amount of possible light.
Greetings
Heya mengalva, get a hold of a ellipsidal reflector, trust me, its 10x brighter then the par job.
Trev🙂
Trev🙂
Heya Rox, the reflector he is using is a parabolic so your theroys are going to be very different then what he is working with 😉.
Trev🙂
i don´t agree with you on this ace 😀
if a elipsoidal output is larger than 20 degrees, then the light would be wasted as well. He worked out that 20 degrees are ideal for him, then with a par20 he would idealy get 100% of light.
most of elipsoidal refelctors i have seen are larger light cone angle output. Just the setup you have would tell you what the best solution is for you.
if a elipsoidal output is larger than 20 degrees, then the light would be wasted as well. He worked out that 20 degrees are ideal for him, then with a par20 he would idealy get 100% of light.
most of elipsoidal refelctors i have seen are larger light cone angle output. Just the setup you have would tell you what the best solution is for you.
a parabolic refelctor doesn´t need to project paralell light always
par20, par30.. par60 do you know what do they mean?
par20, par30.. par60 do you know what do they mean?
Ya its the angles of the light comming from the reflector. Rox, trust me, ive had mine setup with 2 elliptical reflectors now in a test bed and by far it out paces any reflector ive ever fooled with, (that would be a total of 18 of them).
That kinda comes from the efficentcy in the design, and the coating and those reflectors that are being used as in the par reflectors dont have a decent surface on them at all. A par reflector will typically give the result of a 250w setup with a 150w mh bulb, an ellipsidal will give you the result of the 250w being 2-3x brighter on a 150w mh bulb. Big diff.
The ultimate angle to use on a rear focal frensel of 220mm from memory i worked out to be about a par 40 on a 7inch lcd, but they dont make par 40s to my knewlegde and thats why the light has to be moved back. And this is not politically correct in the optical world of projectors on these frensels and you will get rings if you have a split frensel design.
On a side note dont think the reflector has to be that big either in a par design in order for it to work properly, the angle is what needs to be correct. Typically a 60mm par reflector with a 40deg spec will work a whole lot better then a 100mm 40deg par reflector. Take a look at ohps that use halogen, have you seen the size of their par reflectors? TINY!!!! (infact i fitted a cdm-t in one). And the smaller that reflector is the more even your light will be, why? Read my thread 😉 .
Trev🙂
Hey Ace, I've seen your threads about this topic. In the beginings of my project I search a lot in my country for a place where I can buy ellipsoidal reflectors without success, thats why I decided to try the PAR 30 design.
Do you Know if OSRAM, Sylvania or Phillips make commercial lamps like the PAR30, PAR20 but with ellipsoidal body?
Hey Rox, I said a PAR20 with 10 grades or less of angle beam 🙂
About the meaning of PAR20,Par30, PAR38, ... I don't have the answer but it could be educational if some one knows this to share with us 🙂
Greetings
ace3000_1 said:
Please could you tell me what does mean "test bed" i rear it elsewhere but hano no idea what does it mean 😀 (has noting to do with proyectors but i want to learn more english 😀)
now about the reflectors;
i would say that all depends on the setup, for instance this boy i don´t remenber right now, needed to place the bulb at 62cm. This means that he needs very small solid angle from the lamp. So a par20 would do a good work to him.
i don´t know what solid angle do you take from your eliptical reflector but would say it is much larger than 20 degrees. Then this eliptical reflector would not work right when placed at 62 cm.
about reading your thread, 😀 you mean all 100 pages? 😀😀
when i get bored, i use to read some pages there, is very intersting 😀
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