OK, I've noticed that there are a lot of people asking if such and such size LCD will fit onto such and such fresnel. I think this pic should answer those questions effectivly.
I've tried to include the largest standard size in the 2 main categories: Standard and Widescreen
If there is a larger standard size that still might fit let me know, I'll put it in the drawing.

There are also 21.3 inch "4:3" LCDs, they're ever so slightly wider than the pro fresnel.

[edit]I've updated the image to include the dimensions. These are not measured but based on their resolution and the diagnal measurement of the actual pixels. They should be pretty close, but if they're wrong please let me know!

I didnt understand, i am brazilian. Sorry, but my question is: Which one should i use with my 15.4" widescreen lcd.

Thanks

I would say that it should be fine. I am using the standard lense with my 17 inch and while the corners are "slightly" dim with full (4:3) screen mode, I don't have any problems in widescreen.

The main reason you would want the Pro lense with a 15.4 inch LCD would be the longer through distance.

Edit: missed the fact that you were talking about the fresnels and not the lense

You'll need to get the pro fresnels (since the biggest the standard fresnel will fit is a 14" widescreen).

What is the ratio to LCD size to Fresnel size -- how much bigger does the fresnel have to be than the LCD, in terms of both width and height?

It really depends if you use a split or unsplit setup. But the general rule is about 1/2" on each side and top/bottom.

Thanks, going with the unsplit.

Spent at least an hour and a half trying to find the answer for that

If you use a pro fresnel lens with a LCD that is just a little too big for the standard fresnel set, can you cut the fresnel down to size?

Yes, you can cut them down. The way I did mine I just used a utility knife and scribed it real good then just snapeed it over my desk worked great. Also you want to cut the same amount of each end. In other words if you need to take an inch off the total length you would cut 1/2 inch off each end. and also the same for the top and bottm. Good luck

I noticed the other day that the front pro fresnel lens is a different focal length. So I went ahead and ordered the matching ones from another site (3dlens)