im using a 10" lcd panel and have a projection lens with focal length of 285-310mm. Im pretty sure that i need a fresnel to go after the lcd panel with a focal length of about about 300mm.
My question is what focal length should i use for the fresnel which goes between the light and lcd panel?
I have seen people using two fresnels both of about 300mm and then other people using a rear fresnel of 220mm and the front one of 300mm.
Getting cunfused now lol
can anyone help?
pretty please? 😀
My question is what focal length should i use for the fresnel which goes between the light and lcd panel?
I have seen people using two fresnels both of about 300mm and then other people using a rear fresnel of 220mm and the front one of 300mm.
Getting cunfused now lol
can anyone help?
pretty please? 😀
Hi Phillip,
My understanding of it was that you'd use the longer focal length rear fresnel in conjunction with larger screens (17"> etc). Unless I'm completely mistaken, if you were to use a very large screen and a small FL fresnel the light wouldn't cover the whole lens at the desired distance.
I can you tell you definitly from personal experience that a 220mm FL rear fresnel will be fine for a 10" display 🙂 (I use one on a 15" pannel).
My understanding of it was that you'd use the longer focal length rear fresnel in conjunction with larger screens (17"> etc). Unless I'm completely mistaken, if you were to use a very large screen and a small FL fresnel the light wouldn't cover the whole lens at the desired distance.
I can you tell you definitly from personal experience that a 220mm FL rear fresnel will be fine for a 10" display 🙂 (I use one on a 15" pannel).
fresnels
The focal length of the condensor fresnel doesn't matter too much. If you use a 220 mm fl, then put it 220 mm from the lamp arc. If you use a 300 mm fl, then put it 300 mm from the lamp arc.
The field fresnel should be a bit longer than the projection lens focal length, since you are not putting your screen at an infinite distance. (So the the distance from the LCD to the lens will be more than the projection lens focal length.)
I think a standard 220 mm & 330 mm fl fresnel pair would work fine for you.
The focal length of the condensor fresnel doesn't matter too much. If you use a 220 mm fl, then put it 220 mm from the lamp arc. If you use a 300 mm fl, then put it 300 mm from the lamp arc.
The field fresnel should be a bit longer than the projection lens focal length, since you are not putting your screen at an infinite distance. (So the the distance from the LCD to the lens will be more than the projection lens focal length.)
I think a standard 220 mm & 330 mm fl fresnel pair would work fine for you.
Thats great, thanks for the help! just what i needed to know 🙂
Right only need, just need to wait for one cold mirror one Front surface mirror and to get building now!
oh... and i need to try n get a UV filter.... mission if you in the uk..... to get cheap that is.
Right only need, just need to wait for one cold mirror one Front surface mirror and to get building now!
oh... and i need to try n get a UV filter.... mission if you in the uk..... to get cheap that is.
UV filter
polycarbonate (like Lexan XL) or acrylic (like Plexiglas) are both very good UV filters. Lexan is often used for increasing the strength of windows, since you can beat it with a hammer without breaking it. Highly transparent to visible light (high-end glasses are made with it). You might be able to find it in a home improvement shop. The Lexan XL has a special UV blocking coating on one side to prevent yellowing over time. This should be much cheaper than special glass.
polycarbonate (like Lexan XL) or acrylic (like Plexiglas) are both very good UV filters. Lexan is often used for increasing the strength of windows, since you can beat it with a hammer without breaking it. Highly transparent to visible light (high-end glasses are made with it). You might be able to find it in a home improvement shop. The Lexan XL has a special UV blocking coating on one side to prevent yellowing over time. This should be much cheaper than special glass.
Fniding that stuff over here is still easier said than done, but take a look at:
http://www.gcip.co.uk/EP/lexan.htm
If not get in touch with a glazier or picture frame/glass shop.
Have you already bought your bulb Phillip? If you haven't and you're using the common 250w HQI-TS jobs look out for Osram and Sylvania models with built in UV Stop 😎
http://www.gcip.co.uk/EP/lexan.htm
If not get in touch with a glazier or picture frame/glass shop.
Have you already bought your bulb Phillip? If you haven't and you're using the common 250w HQI-TS jobs look out for Osram and Sylvania models with built in UV Stop 😎
I have already got the bulb and ballast, managed to get the whole lot for £65 brand new and that includes shipping.
The bulb is an Osram HQI-T 400w\N\SI
not sure what all that means though
The bulb is an Osram HQI-T 400w\N\SI
not sure what all that means though
Lexan in the UK
http://www.gcip.co.uk/EP/lexan.htm
The Lexan EXELL D would be perfect. It has UV blocking on both sides, so you don't have to worry about getting it facing the wrong way. This coated Lexan blocks more that 99.9% of the UV. The glass on UV-stop lamps only blocks around 90%. That 10% will bleach out your LCD color filters and damage your acrylic fresnels.
http://www.gcip.co.uk/EP/lexan.htm
The Lexan EXELL D would be perfect. It has UV blocking on both sides, so you don't have to worry about getting it facing the wrong way. This coated Lexan blocks more that 99.9% of the UV. The glass on UV-stop lamps only blocks around 90%. That 10% will bleach out your LCD color filters and damage your acrylic fresnels.
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