Hi,
 
Firstly apologies for this email being in English. My fresnch is unfortunately not good enough to comunicate my problem; i hope that your English is better!
 
I have built a projector with a  
 
hami 8"
 
250W HQL metal hallide light
 
Exlcusiv optic set with fresnels of 160/305
 
Everything looks good and I am happy with my image apart from on white scenes (or with no image showing) i get a ring in the middle of my image (only 1).
 
I am curretnly using the fesnels in split mode, but have previously tried unsplit and a different set of fresnels (also form exclusiv).
 
The distances between my fresnel/lcd/frenel is 25cm/15cm
 
I have ruled out the light and mirror being the problem so I was wondering if anyone else had experienced this problem? Not all the rings are a problem, only the center most one and the one surrounding it.
 
Thanks for any help and good luck in the World Cup; i though France's victory over Brazil was fantastic
 
Matt

Good evening.
 
Your problem is due to the very bad quality of EXCLUSIF's fresnels: they create an hot spot in the middle of your projection.
 
Buy new fresnels at IZZOTEK's shop and your problem will disappear by magic !!!!  

No probleme we speak english too !
My english is not very good but i'm sure we can understand a little.
 
Yes he is right. The probleme came from the fresnel.

Hello,
 
As others said, it's a know problem of the exclusiv's fresnel lens.
 
This problem is highlight when you're using a short arc light bulb. (mich33's pic)
 
 

Ahhh, thanks alot.
 
Glad i left some space in my projector for modification now!
 
How hard is it to accurately cut the fresnels? I need them 200 wide to fit my projector and it seems
the izzotek ones are 240?
 
Is the exclusiv triplet ok or should I get another one of thesefrom izzotek too?
 
Matt

Hi,
You can also try moving the first fresnel back further from the lcd (if you have split them), as that seems to have improved things in my case.
 
Otherwise the best ways to cut the fresnels is either with a metal saw (hacksaw), or you can use a cutter and a straight edge to score the plastic a few times then it should break cleanly.
 
Its also a good idea to drill holes in the corners while they are still joined so you can line them up easily after you have cut them (the threaded rod technique)
 
Afaik it's only the fresnels that have a problem

To cut and spil your fresnel you can do like that :
 
You follow the instruction of mich33 and you won't have any problème.
 

 
Puis découpage au cutter : on passe d'abord beaucoup de fois au cutter pour faire un trait profond, puis on casse la Fresnel à cet endroit sur un bord de table. C'est assez net et c'est pas très compliqué. (la scie sauteuse, c'était finalement un peu trop bourrin... )

 
Photo take on the trippel project of Ppsoft Here

Thanks alot for all the help.
 
I already have my rear fresnel 25mm from the LCD and it is only really noticable on light scenes. I have ordered some Fresnels from Izzotek and hopefully will be ok cutting them
 
Thanks,
 
Matt

Let me give you some more pictures about how to split and cut Fresnel lenses :
 

 

 

 

 

 

 

 

 
Hope those pictures can help...
 
see u