Question about aspherics

I'm in the process of building a light for a friend. I'm using a Romison RC-G2 for the body and this lens. Unfortunately, it doesn't do what I need it to do, which is to go from a tight focus to a flood within the amount of travel allowed by turning the head. Should I be looking at a much rounder aspheric? Any suggestions in particular? The one I used is 21mm but a mm or two larger would still physically fit.

Oh, and it seems Romison is using a much improved driver on the RC-G2. The older ones have a really lousy driver which pulls 2 amps and only drives the LED at maybe 175 mA. The new ones pull about the same, but drive it at better than 500 mA. In other words, no need to change out the driver like before.

Do you have a tight focus? If not, the parameter you are looking for is focal length, which is the distance from the lens to the focal point. The LED is positioned in the focal point for maximum focus.

I would also guess that the fattest lenses will have the shortest focal lengths, and that these will give the biggest de-focusing effect when moving the LED slightly away from the focal point. But I'm not really that much into optics.

jtr1962 said:

I'm in the process of building a light for a friend. I'm using a Romison RC-G2 for the body and this lens. Unfortunately, it doesn't do what I need it to do, which is to go from a tight focus to a flood within the amount of travel allowed by turning the head. Should I be looking at a much rounder aspheric? Any suggestions in particular? The one I used is 21mm but a mm or two larger would still physically fit.

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In playing with my different built apherics and small loose lenses but I can't really get any of them to produce a flood beam. Theoretically, you'd screw the head down tighter moving the LED closer to the lens but this normally still produces a rather tight beam with a big donut hole. Instead, the adjustments on my lights only focuses or de-focuses the projection of the LED die.

jankj said:

Do you have a tight focus? If not, the parameter you are looking for is focal length, which is the distance from the lens to the focal point. The LED is positioned in the focal point for maximum focus.

Click to expand...

Tight focus works fine (or it will once I put a spacer under the LED). Problem is that I'm interested in going from that to a defocused beam in maybe about 3/16" head travel. All I end up with is a slightly less focused projection of the LED die like Patriot mentioned. But I get the effect I want if the lens is moved much further away (or closer). Problem is I can't go from flood to focused in the amount of travel allowed by the head, and realistically there's no way to increase the amount of head travel (it's obviously a function of the thread pitch and number of threads).

I would also guess that the fattest lenses will have the shortest focal lengths, and that these will give the biggest de-focusing effect when moving the LED slightly away from the focal point. But I'm not really that much into optics.

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That's what I was thinking here but I need to find out who sells them. Nothing else DX has really seems much different from what I'm using.

Running an Aspheric at 1/4 the focal length has produced nice beams in my experience, they will lack a hotspot but instead will be a perfectly circle of even light. The aspheric will still blue shift the color a bit though, so keep that in mind.

I own several aspherical lights and i didn't think you could have a flood beam with aspherical lenses just throw.

If you move the lens so the LED no longer is in the focal point you get a wide, even circle of light. Not really an all flood light. It looks more like if you removed the "hot spot" part and just kept the spill section of a conventional reflector light. If you have a Maglite modified with aspheric (such as the aspheric kit from KD) you can do this by unscrewing the head partially. Other lights may have to few threads to do this, but you can get an idea by holding the aspheric part in your hand.

I think this thread might do better in the H&M section, so I'll move it there.

Hi Jtr,
the X2000 and C30 focusing torches I have have a travel of approximately 8mm from full focus to full flood. Ignoring the flat surround on the plastic lense it measures approx 21mmx8mm deep. In full flood mode the back of the lense is approx 3mm from the top of the xr-e dome.
The X2000 was the first torch I've ever actually bought and I find the even flood very easy on the eyes compared to the burning hotspot of the Ultrafire A10 I have on 14500's, although I still have the option of good throw.
Why not just cheat and risk 10 dollars on the C78 they have just got in?

Hope this helps

Paul.

Thanks for moving the thread, DM51! I agree it'll probably do better here.

I assume this is the light you're referring to, Paul. Heck, for $10 I'm going to order a few. It seems like it might be perfect! Saves me a lot of work, and maybe gives me some ideas as well. Thanks for the find!

It looks like the C78 is indeed using a deeper lens. I would still be interesting in obtaining a few lenses like that if anyone knows where they're sold (nothing on DX last I checked).

No problem I'm waiting on a couple of user reviews to make sure it's not too cheap and nasty before I buy a couple for presents.
Maybe challenge yourself to make an AAA version? I want a 3 mode focusing EDC Cree XP-G if you want to make a couple :thumbsup: lol. I reckon they would sell by the bucketload!

Paul.

Edit: Maybe try googling RC-29 if you think Romisen may be superior? Theres a Q5 version out for a bit more.

option a:
rc-29
http://www.kaidomain.com/ProductDetails.aspx?ProductId=9864
$15.69

option b:

x2000 lens






16000 lux @ 1m at 2.2 amp and 18000 lux @ 1m at 2.75 amp with this circuit http://www.dealextreme.com/details.dx/sku.7882 and cree XR-E package ez900 chip q5 bin powered with 14500 battery

for flood change put a diffuser in front of the aspherical
the shorter the focal length (within the ability to BE in focus) the shorter the length of de-focus. so with a more pregnant lens , you can get a shorter focal length and a shorter de-focus to wide length.
de-focus isnt going to be a flood, but its the most beautifull round wide circle.
with something as simple as transparency tape over the front lens, you can disperce the light to more floody quick.

with difussion below next to the led itself, you can blend out the light (at high losses) of the emitter to get rid of emitter projection, like the grid lines, or quad die seperations, but it doesnt ruin the long throw projecting as much, and it wont make it wide.

on my moveable head aspherics, the small one only goes from super spot square to spot blended square, head only moves about 1/3rd of an inch. The mag one the head can move huge distances, with many turns, and can go from super square spot, to wide purdy circle beam

Hi JTR, did you purchace any lights in the end? I bought a C78 for a friend, recieved it a couple of weeks ago, he's very happy with it and it seemed like excellent quality for the price! I've also just received a couple of the RC-29's. Even better quality if anything and a better design for heat dissipation I should think. I might try and swap the Ultrafire A10 driver into one and vise versa so I can run it on 14500's. I cant find a cheap 14mm boost driver that accepts the voltage range of the A10

Paul.

Paul Baldwin said:

Hi JTR, did you purchace any lights in the end? I bought a C78 for a friend, recieved it a couple of weeks ago, he's very happy with it and it seemed like excellent quality for the price! I've also just received a couple of the RC-29's. Even better quality if anything and a better design for heat dissipation I should think. I might try and swap the Ultrafire A10 driver into one and vise versa so I can run it on 14500's. I cant find a cheap 14mm boost driver that accepts the voltage range of the A10

Paul.

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I have too the rc-29 its nice with only 1xaa it give 6800 lux@1m and bypassing the switch and spring 10800 lux @1m

current draw bypassing spring its around 4 amp!!!!! maybe around 1 amp to the led it have the best circuit for 1xaa i never saw ... the spring of this flashlight like the spring of rc-g2 its too bad

but i will upgrade too for more power with 14500 and sku 7882 (max 3 amp) but I recommend set it at around 2.2 amp max at battery ........1.3-1.8 amp its maybe better if you don't really need the max power possible

edit loool I have too the c78 like you (cheap copy of ledlenser p5) it gives 5800 lux@ 1 m i prefer the slide system of this flashlight but the board of the c78 its too small, no way to upgrade

Hi moviles,
I see what you mean! Shorting across from battery base to torch body with a piece of wire makes quite a difference. So is it the spring or the switch or both? I've got nothing to measure it with at the mo, will it help if I solder a wire from the base of the spring to the top?

:rock:RC-29 CR2

I really like the X2000 flood-to-zoom:



Of course, that's the poor thing disassembled. My 3 were bright, easy to adjust (and they stay adjusted), and didn't fall apart on me.

I had several X-2000 before the romisen came out with their version of the
Flood to Zoom (Including the RC-29). The Romisens have a better build quality, smaller & brighter die image than the X-2000 I had. More attractive looking & also is more slim than the X-2000, plus it comes with Q5 instead of P4 for a very similar low price.

My CR2 version (Cut down from AA version RC-29) pictured above retains the flood to zoom function as well.