Hey smart people,

I've got a 15.4" lcd and I'd like to use the "standard lens" triplet. However, I'm less sure about the "standard lens" fresnels. It says they're for use with a 15" or smaller LCD... looks like I'm .4" too big.

What should I be getting?

Many thanks...

Replying to my own post! Cool!

Anyway, I found these fresnels at http://3dlens.com/largefresnellens.htm

395mm x 395mm
Thickness: 2mm
Weight: 350 grams
Material: optical acrylic
Groove pitch: 0.5mm
Focal length: 330mm

and

395mm x 395mm
Item: #A395b
Thickness: 2mm
Weight: 350 grams
Material: optical acrylic
Groove pitch: 0.5mm
Focal length: 220mm

Would these be more appropriate than LL's for my 15.4" lcd?

Yep that's the fressies you need.

Listen to this man. He is a genius when it comes to making a great picture. I think his pj results are one of

the best of LL.

Thank you jonjandran and Kryptonian!

been lurking for a while, this is my first post.

There are two more fresnels on that site with the same focal lengthes as the ones op posted: 330/220. The only difference being the other lens have a groove pitch of 0.2mm. I am just wondering what difference if any does groove pitch make for our application. And if so should i go with the finer one instead? Thanks.

I presume that site is 3dlens and the greater the pitch the 0.5mm ones will let more light in, but the 0.2mm will produce a clearer image. Thats from what I can gather anyway. Odly enough, the 0.2mm is cheaper than the 0.5. I contacted 3dlens and asked them what would be best for a DIY projector, and they said the 0.2mm- I was wondering, because it would seem that they would try to upsell and sell the more expensive
0.5mm. I'm not entirely sure what would be best for us, or that there would be much of a difference in the picture.

I'm sure someone will respond with the correct answer though.

Are the 3dlens fresnels you mentioned better than the LL pro fresnels? If so, why?

They're different . The LLPro Fresnels are big enouh for up to a 19" Lcd but they have a Fl of 610mm/220mm. The standard lens have a focal length of 330mm/220mm but they are only bg enough for a 15" Lcd.

So you need a 330mm/220mm that ar larger to cover a larger Lcd. Hence the 3dlens Fresnels.

And the 5mm or the 2mm will work and it would be VERY hard to tell any difference in a projector. So go with the cheaper one

I really really appreciate your fast reply, but for some reason I cannot seem to understand it.... I wanna learn more about this, but for some reason the wording in your reply makes it hard for me to understand. Of course I understand your baseline - go for the cheaper LL ones, but I still want to know why. Could you please reword it in more detail? Thanks... I'm sorry for asking.

I want to say to you jonjandran - Your projector is great. It is the one I will be building and it will be great

Hmm what part don't you understand ?

There are no diferences in the quality of the 5mm (groove pitch) fresnels (330mm and 20mm)from LL or from 3dlens. They just are different sizes. The 3dlens are larger so they can be used with larger Lcds, the LL standad fresnels are smaller so they are only large enogh for 15".

The LL Pro fresnles are a different focal length. This is because the Pro triplet has a longer focal length for increased throw. So the fresnels have to match the triplet.

So it's not a matter of which is better , it's a matter of which is the right one for what you need to do.

That perfectly answered my question... I don't know which part I didn't understand. I'm not a native English speaker so that might have thrown me off. I get it now though, thanks a lot!