I just ordered this a few hours ago. Going to resurrect an old old build. It's actually a perfect fit.
I don't think sandwiching two is the best idea, the amount you lose at the interface between the two lenses can be exemplified by cracked glass.
Yeah, this is how I understand it, assuming everything else is the same,
100mm lens with low convex profile - long focal length, project smaller spot (lesser light captured)
100mm lens with higher convex profile - shorter focal length, project larger spot (more light captured)
But they both have the same light intensity in the spot.
You may use dual-lens system to ‘shorten’ the the focal length of the 100mm lens - resulting a larger projected spot with still the same intensity.
(I might not use the correct technical terms here.)
Maybe focal length is 140mm same as I got 2 from DX.
http://dx.com/p/99mm-replacement-glass-lens-for-flashlights-43043
I ordered one of their smaller lenses but don’t have it yet.
It adds a couple extra reflective surfaces but back to back, the focal point should be closer and capture more light. Bridging that thin gap with optically clear silicone could eliminate or at least drastically reduce those reflections.
Very clean. No I haven’t tried it yet. I thank you for showing us this lens. It might come in handy if I need some lens-changing in the future.
I have no doubts that that lens would make one hell of a thrower. That’s obvious because its close to frisbee sized.
LOL VFM.
Way to go Ramblings. Now lets see what we can do with these bad boys (Well, I hope they kick ass).
POK wrote:
Maybe focal length is 140mm same as I got 2 from DX.
http://dx.com/p/99mm-replacement-glass-lens-for-flashlights-43043
Interesting. Says 80mm in the link, but I'm not surprised it is wrong. Are they actually 24mm thick as advertized? If so, they it would seem the lens in the OP would have an even longer FL since it is only 19mm thick. How are the lenses working for you?
“How are the lenses working for you?”
badddddd
Sorry to hear that. Thanks for reporting. I take it it doesn't focus clearly?
I'm starting to like DX, but it seems their line of aspheric lenses is quite sub-par. Lets hope this FT lens is a good one.
Deal Alert. OP updated
Yowza! 790k from XML2, especially 400k from MTG2 is quite… insane! Especially one you can build at lower budget.
What’s the approximate focal length of this lens?
Focal length is about 5.5" (about 14 cm).
Had to get out to try it out. This lens has to be built into a zoomie because fully focused you need binoculars to see out far enough to to use the hot spot. The hot spot is too small within the range of normal eye sight. Check you my 20 minute to build light:
Here is a beam shot aiming at a 70 foot tall pine tree. Pine trees love to eat up light. Distance to the tree is about 250 feet.
LOL. Yeah, totally surprised me too. I expected junk for $9. I'm thinking the issue is that it might focus the image of the die with some artifacts. Could just be my set up though with the white PVC. Well, I have to crash for work tomorrow. Night folks.
Wow, very nice results! But wait a minute…something looks familiar…did you steal jmpaul320’s camera and technique?
Hahaha… can’t blame him, that IS a popular technique nowadays! :bigsmile:
At 14cm FL, this FT lens is pretty much the same thing as DX, only $1.10 cheaper. Nice. Quite tempted to try this as well, except that I still have 62mm project lens laying around almost a year… with the project not even starting LOL. Maybe I’ll try 100mm after actually finishing that.