Reflector confusion.

Hey guys,
I'm in need of something clearing up.
I've been looking at OP reflectors and have seen a few conflicting bits of info.
I was under the impression they increase the amount of spill and provide a more diffuse hot spot reducing throw but some bits of info I have seen that have been 'backed up' with numbers suggest an OP reflector increases the cd of the hotspot and increases throw whilst also providing a brighter spill.
Now to add some context to the situation my current setup was an XM-L2 with a SMO reflector, I'm now changing over to a dedomed XM-L2 and have an OP reflector sat here to possibly pair with it. I was thinking that as more light exits forwards from a dedomed led that the OP reflector would help keep a relatively 'bright' spill but having read a few contrasting things can someone help me understand what I'm likely to get as a result.
My available options are
1. Domed SMO
2. Domed OP
3. Dedomed SMO
4. Dedomed OP
If someone can give me a brief rundown of what sort of beam profile each combination will provide that would be greatly appreciated and will save me a lot of faffing about testing out each combo.
Also to give a bit more info as to what one after I'm looking to build a good compromise light.
I gave a friend a C8 with SMO and XPL hi, the hot spot was too tight and spill to dim for my liking. Mine with the xml2 with SMO had a nice large slightly diffuse hot spot but the spill was a bit brighter than it needed to be, great for walking down narrow lanes but terrible for in tighter pack spaces like dense woodland as the back scatter from the spill made it quite hard to focus at farther distances.
Sorry for the rather wordy post.
Thanks in advance for any advice.

You where right at the beginning op reflctor make a brighter spill and less cd (les throw) but it make a smother beam
So

Dome on op- floodiest of all shortest range and brightest spill

Dome on smo- more throw then with op so spill is not as bright

Dedomed op - i think it has more throw than dome on smo but i am not sure but it will have smother beam

Dedomed smo - most throw dimest spill

Brilliant, thankyou for that info.

Right then I will add onto this rather than start new. Reading back though some of my threads I noticed someone mention focusing a flashlight. What exactly does this mean, how do you go about focusing a flashlight and what does an out of focus flashlight beam look like.
I have PM'd the guy who mentioned it to get his thoughts/advice but I thought I'd ask the rest of you aswell to see what your views/experiences are.
Thanks
Thom.

Some lights have a lens setup instead of a reflector. When the lens is totally unfocused it provides a nice wide beam with no hot spot. As one brings the LED into focus the beam narrows and becomes brighter. When it is completely focused the beam is rectangular since it is focusing the image of the emitter. One can see the dark areas in the image between the individual parts of the emitter. At that point, there is no spill whatsoever.

Some people like the ability to switch between a smooth flood without much throw and a tightly focused beam with no spill. I have a couple of cheap Meco lights that focus, and frankly, I am not impressed. To each his own I guess.

Ok I should clarify I'm not on about zoomies, the post I'm referring to mentioned a lot of trial and error filing something down to focus the beam and I have seen mentioned on the other forum people saying they removed then centering ring on the reflector so it sat lower which changed their beam profile.

Thom2022 said:

Ok I should clarify I'm not on about zoomies, the post I'm referring to mentioned a lot of trial and error filing something down to focus the beam and I have seen mentioned on the other forum people saying they removed then centering ring on the reflector so it sat lower which changed their beam profile.

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Reflectors are parabolic, that is in a perfect world with a point light source located at the focus all of the light would exit the reflector collimated into a beam with no spill. Since LEDs, while close, aren't a point light source, there are some rays that do not exit collimated, but slightly off axis. This is where spill comes from. The larger the emitter, the more spill in relation to the center of the beam, commonly called the hot spot.

I haven't taken time to do the math on an emitter located out past the focus, but it can't do anything but create more spill, thus lessening the amount of light going into the hot spot and reducing the throw while enlarging the spill.

Definition: Collimated - all rays traveling in the same direction, ie parallel. A laser beam is an example of essentially perfect collimation, while a lit match exhibits no collimation whatsoever.

So then by that explanation, moving the reflector in relation to the led will have an effect on beam and it could be possible to 'catch' more light on the reflector and improving hot spot intensity but chances are (quite high) I will balls it up and it best be left alone.
Forgive the proper idiot speak, it's 12:36 am and I've had a few more than a few to many.

Yes, adjusting reflector 'up' and 'down' in relation to the LED can improve the beam if the reflector wasn't initially set optimally.
Some have removed ringy beams and tightened up the hotspot by adjusting the reflector.
Btw, these adjustments are usually a fraction of millimeter adjustments.

An xpl hi is just a dedomed xpl. . Should be superior to any dedomed xml2, based on spec sheet. . I am pretty sure my xpl hi is as bright, as my xml2 u2 bin, at 2 watts. Maybe a few lumens brighter.. Maybe you had one laying around.

Superior is a very relative term. For throw I don't doubt. For a balance of throw and spill not so much. The tight hot spot and dim spill are the reason I gave away my XPL hi fitted C8 as a gift. The domed xml had too bright a spill so hopefully a dedomed Xml will provide the middle ground I require.

Using petrol, acetone? My preference would be acetone. Probably faster. I bonked too many dedomings before mastering. Always too many lumen drop. I must be damaging something. But lumen drop is to be expected. The lumen Flux of an xpl hi is on our with a u2, or can be if you pay enough. Maybe start with a u4 bin.

My xpl hi in a 30mm smooth has good spill, about 12500 candela at 700 ma. Better spill than my xml2 in a 42mm which has only 8000 candela. My second xpl in a 30mm at max of 320ma, is rather tight, but I forget the candela. Anyway, it is hard for an amateur, with a fussy beam pattern taste, to choose a good reflector for any given emitter. Too many variables. However, it is even harder to choose a ready made light, and get the beam you like. Even harder, when you don't have a brick and mortar with an unconditional return policy.

If you are moving from a domed emitter to one without, then lowering the reflector by half the height of the dome should put the spill and beam back to close to what they were before, except that there will be a little less spill and a little more light in the hot spot.

Visualize a domed emitter. The focus I mentioned will be in the center of the dome and halfway between the top of the dome and the surface of the emitter. This means that some of the light is coming from in front of the focus, and some is coming off axis from the side of the dome. That means a relatively wider spill and dimmer hot spot than from a correctly positioned planar emitter. Lowering the reflector by half the height of the dome will place the focus back onto the surface of the emitter where it should be. Since without the dome the emitter is closer to a point light source, the spill should decrease slightly, and there should be more lux in the hot spot. If you are de-doming an emitter, or swapping an undomed emitter for a domed one, you will have to readjust the reflector to really obtain the results you are looking for.

Timothybil said:

If you are moving from a domed emitter to one without, then lowering the reflector by half the height of the dome should put the spill and beam back to close to what they were before, except that there will be a little less spill and a little more light in the hot spot.

Visualize a domed emitter. The focus I mentioned will be in the center of the dome and halfway between the top of the dome and the surface of the emitter. This means that some of the light is coming from in front of the focus, and some is coming off axis from the side of the dome. That means a relatively wider spill and dimmer hot spot than from a correctly positioned planar emitter. Lowering the reflector by half the height of the dome will place the focus back onto the surface of the emitter where it should be. Since without the dome the emitter is closer to a point light source, the spill should decrease slightly, and there should be more lux in the hot spot. If you are de-doming an emitter, or swapping an undomed emitter for a domed one, you will have to readjust the reflector to really obtain the results you are looking for.

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Every now and then a great post comes out, where I wish, beside the reply, we had a scrapbook button. Years later, we could reread the post, lest one day, we forget a gem that our busy life interposed it's cares upon the neural pathways that could have made smart use of the information.

That's a brilliant bit of info. Thankyou. I guess I'm in luck as I can just shave down the back of my led centering ring so the reflector sits a tad deeper and if I screw it up/change emitters I can just replace the ring with an intact one. I wil just be careful that lowering the reflector doesn't cause a short.

Thom2022 said:

That's a brilliant bit of info. Thankyou. I guess I'm in luck as I can just shave down the back of my led centering ring so the reflector sits a tad deeper and if I screw it up/change emitters I can just replace the ring with an intact one. I wil just be careful that lowering the reflector doesn't cause a short.

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I put a thin layer of 5min epoxy resin on electric solder points. Doesn't hurt if ingress of water into this area.. Very important.

So just an update. I sanded the led centering ring down so the flared base is practically paper thin, used a drift and hammer to gently tap the solder joints flat and wrapped the bottom section of the reflector in electrical tape just incase. Overall the reflector sits about 3/4-1mm lower and the hotspot has tightened up and intensified a noticeable amount, it also appears sharper. Very happy now with this light, the spill is noticeably dimmer than with the domed led but is now ideal for its purpose. Thanks for all the advice guys.

degarb said:

Every now and then a great post comes out, where I wish, beside the reply, we had a scrapbook button. Years later, we could reread the post, lest one day, we forget a gem that our busy life interposed it's cares upon the neural pathways that could have made smart use of the information.

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Thank you. I try to not be too technical but it is sometimes hard to explain things without being so. I spent six months writing and debugging a program for creating parabolas and other quadratic figures, so I don't think I will every forget what makes them tick.