All three of these Triplets have clear through Aperatures of of 1.5". However, their lengths vary (this affects field angle?) and their outer lenses also vary in size.

Outer lens diameter: 1.5", 3" and 2" in respect to the two photos.


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Which gathers more light (higher speed) or are they all the same?

Where did you buy them?

The two on the right are on loan, the left was an ebay item. I think the standard LL Triplet has bigger aperatufes and a person probably should just use that. Anyways, can anyone answer the question?

Depending on how the lenses are arranged, ones with a larger inlet and outlet lens may gather more light, but if all are the same FL, and have the same through aperature, most likely they will all be equivalent in terms of light gathering ability.

In order to gather more light, it needs to be able to let more through.

Think if it this way. Using a lens and sunlight to fry ants, the larger the lens, the hotter the "hot spot", because it can gather the most area of sunlight to concentrate to a point. The only usable lens area is the area that goes through.

If we had a point source light (We don't,) zero diffusion of light through the LCD (We don't have that either) then the area of the triplet would be irrelevant. We could literally use a pinhole camera as a projection lens. Focus at any distance from zero to infinity. As is, we need a lens large enough to capture the light once the light engine and LCD are through with it. The 80mm triplet (Somewhat smaller in effective lens diameter) is almost large enough. A 100mm lens would be better, but more difficult to source, and more expensive.

Thanks for the very good answer, but in the end you don't know either. I did manage to find myself some good quality 100mm lenses, I just don't know when they will arrive.