I wonder how does it compare with zoomies using aspherical lens.
Some measurements show that 50% of the lens is used when focussed.
That’s significantly better than 30% of course, but still only half of what it should be.
I hope to finish opening the inside of the head today so that 100% of the lens is used when focussed.
I did one very unscientific test but it proves what Jerommel is talking about.
Specs of my HT08:
Dedomed XPL led
Blf Fet+1 driver
Samsung 25R battery
I measured throw twice in a row with same battery one right after another. First test was with light assembled as intended to work, measured intensity was 45kcd.
Next i disassembled the light and took the lens in front of the light like this:
This way the lens will capture as much light as possible. This way the light gave intensity of 113kcd.
Well, there you go. :+1:
Not much response in the other thread, so i’ll post my solution here too:
So that problem is solved now.
The whole lens is used now when focussed.
But the tail cap threads are pretty bad too.
No idea how to tackle that problem yet…
Did you notice an improvement in throw ?
I was too late for the HT08 at flashsale, so i didn’t buy it, after Jerommel his explanation i’m glad i didn’t buy it!
Thinking about a triple or quad M1, anyone has tips where to buy a spacer? Kiriba doesn’t have it
What exactly did you do? All I see is you’ve zoom the led at half way point when I tested on my light.
So, i put the HT08 back together again with a resistor mod (another R200 on top of the R200) and a dedomed SST-40.
It pushes 5 Amperes through the SST-40, which should give around 1500 Lumen from the dedomed LED.
I’m not impressed.
I already swapped the AR coated glass lens for a better one, because the stock lens was a little ‘dark’ (as some cheap AR lenses are).
But compared to my modded UF-T20 with dedomed XP-E2 with ‘double lens’ set up on 6x 7135 (2.1 Amperes, around 600 LED lumens i guess) the HT08 is only slightly brighter while giving the same size LED projection.
(My B158 with dedomed XP-G2 on 2.8 Amperes is much brighter, but it has a much smaller LED projection.)
So now i’m doubting the quality of the Fresnel lens of the HT08.
I mean, it’s good at projecting the LED with detail (grid of dots on the die), but it seems the light transmittance of the Fresnel lens is not impressive…
To summarise, i now have a HT08 that gets hot pretty fast but is not significantly brighter or tighter than my modded UF-T20 which uses less than half the power…
I opened up the head, you can see the silver grey surface of where i milled away a lot of aluminum.
(first i removed the retainer ring of course)
o, great… the driver is somehow back to “hi - strobe - sos” group again… :person_facepalming:
i hate this light… :weary:
[edit]
Well, now i got it to group 2 (low - high) fairly easily.
It’s better than group 3 (low - mid - high) because the difference between mid and high is very small…
A few notes from my experience with fresnel lenses as a replacement for aspheric lenses:
- The quality of the fresnel lens matters. I got noticeably more throw from the $28 lens v. the $8 lens.
- Even the best quality fresnel lens will still have far less than throw the cheapest aspheric lens. There is significant unavoidable light loss at the top of each ridge in the fresnel lens.
- In a conventional aspheric lens, a short focal length gives you a wider die image in spot mode, while making the lens thicker. Beam angle in flood mode is narrower because the bezel needs to stick up more to protect the protruding lens.
- In an aspheric lens you can have a very short focal length without any added thickness. This gives you a wide image of the die in spot mode. Also, because the lens doesn’t protrude you can have a wider flood mode than any aspheric.
From what I’ve read of the HT08, the designers made a number of poor choices:
- They used a long focal length-fresnel lens. Using a short focal length lens would have been much better. Throw in spot mode would be the same, but the die image would be bigger and illuminate more. The bezel would also need less travel to cycle modes.
- The exposed screw threads inside the bezel will produce excessive rings around the die image in spot mode. They are muted somewhat due to the anodized black finished, but not having threads there would have been much better as it would have eliminated all rings.
- I do not have this light so can’t confirm, but one poster reported that not all the fresnel lens is being used in throw mode.
Also, I wonder why did they pick a positive focal length lens.
A negative would have the ridges on the inside, making a glass lens at the front unnecessary.
A negative lens would make the beam only wider, but that’s not what you mean.
This lens is plano convex with aspheric shape, but the front is made with rings.
There are also TIR fresnel lenses, but i think you can not zoom with it.
funny, i found this image via google, in an old BLF topic: I want to try better TIR optics
I wished mine worked so I can find out if I wasted my money. Appears to have a defective tail switch
I used the tailcap from my vg10s