Can someone give a brief explanation in the difference in these two emitters? I am a novice and have searched both this site and Google and can't really find a simple answer. I'm considering two similar lights with these two emitters and wondered the difference in throw / flood, etc. Thanks.
Cree XM-L vs. Luminus SST-90?
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MikeAusC
Enlightened
The XM-L can be run up to 3 amps and is a smaller chip
The SST-90 can be run at up to 11 amps, so it will put out more total light, but it's a larger chip and older generation so it will be dimmer for a sharply focussed image, even when drawing a lot more power.
Go to the Cree and Phlatlight sites to download the datasheets.
The SST-90 can be run at up to 11 amps, so it will put out more total light, but it's a larger chip and older generation so it will be dimmer for a sharply focussed image, even when drawing a lot more power.
Go to the Cree and Phlatlight sites to download the datasheets.
XML is good to about 1000 lumens if sinked well. SST-90 is good to about 3000 lumens. But compared to each other, the SST90 is huge next to a XML. Maybe 7-8X bigger, maybe more. The SST90 needs to be in a big flashlight to make it throw due to its size. In smaller lights it makes a great flood though.
Jekyll & Hyde
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Bronco
Enlightened
The SST-90 has an emitter surface area of 9 square millimeters. The XM-L's emitter is 4 square millimeters. Thus if you're looking for a light that can project a tight beam a long distance, the SST will require a much larger reflector. The SST also requires much more amperage to reach its maximum output. That means more and/or bigger batteries unless you're willing to settle for significantly decreased runtimes. This increased amperage also creates lots of heat rather quickly. Figure on seeing 1800 to 2200 actual "out the front" lumens from the SST-90 in most lights. Conversely, the XM-L is more efficient but only capable of around 750 to 1000 lumens in most lights. Still it will provide very good throw with a relatively smaller reflector.
peterharvey73
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The Luminus SST-90 is a 3mm x 3mm square for a total of 9 mm square die size.
The Cree XM-L is 2mm x 2mm for a total of 4mm square die size.
The Cree is newer in design, so it is more efficient.
The Cree XM-L can be driven up to 3 amps within recommended specifications to produce 1000 emitter lumens.
However old, the SST-90 is still much larger in size, so it can withstand more heat build-up, thus it can be driven to 9 amps in recommended specifications to produce some 2200 emitter lumens.
Because the SST-90 is larger in size, and produces more lumen output, it will tend to have a larger hot spot, and have a brighter spill, and more overall flood.
I am not exactly sure of the surface brightness of the SST-90 versus the XM-L, however from my memory, the SST-90 is no slouch in surface brightness at all - in fact it's surface brightness is better than the old XPG-R5, and only slightly inferior to the very old XR-E R2.
Thus, throw will be mostly dictated by the diameter of the reflector, not the surface brightness of the emitter.
Btw, just because the surface area of an emitter is large, it doesn't necessarily mean that it's surface brightness will automatically be low.
Also, just because the emitter is larger, it doesn't mean that it must have a proportionately larger reflector to throw as well as the smaller emitter.
These are common mistakes I use to make myself in the understanding of throw etc.
Don't focus too much on paper specifications, and generalisations about emitters.
At the end of the day, the best way to compare the two flashlights is to switch them on, and test them side by side.
If not possible, look for youtube videos of their beam performance to help.
Or if worse gets to worse, start a new thread on cpf like this one, for help...
The Cree XM-L is 2mm x 2mm for a total of 4mm square die size.
The Cree is newer in design, so it is more efficient.
The Cree XM-L can be driven up to 3 amps within recommended specifications to produce 1000 emitter lumens.
However old, the SST-90 is still much larger in size, so it can withstand more heat build-up, thus it can be driven to 9 amps in recommended specifications to produce some 2200 emitter lumens.
Because the SST-90 is larger in size, and produces more lumen output, it will tend to have a larger hot spot, and have a brighter spill, and more overall flood.
I am not exactly sure of the surface brightness of the SST-90 versus the XM-L, however from my memory, the SST-90 is no slouch in surface brightness at all - in fact it's surface brightness is better than the old XPG-R5, and only slightly inferior to the very old XR-E R2.
Thus, throw will be mostly dictated by the diameter of the reflector, not the surface brightness of the emitter.
Btw, just because the surface area of an emitter is large, it doesn't necessarily mean that it's surface brightness will automatically be low.
Also, just because the emitter is larger, it doesn't mean that it must have a proportionately larger reflector to throw as well as the smaller emitter.
These are common mistakes I use to make myself in the understanding of throw etc.
Don't focus too much on paper specifications, and generalisations about emitters.
At the end of the day, the best way to compare the two flashlights is to switch them on, and test them side by side.
If not possible, look for youtube videos of their beam performance to help.
Or if worse gets to worse, start a new thread on cpf like this one, for help...
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Bronco
Enlightened
I appreciate your attention to detail, but two such seemingly contradictory statements might be confusing to someone like the OP who's relatively new to the high performance flashlight game. If we control for the most important variables (i.e. limit ourselves to discussing reflectored lights, assume that the manufacturers have selected reflector shapes that are reasonably well suited to the respective emitter sizes and allow for similar surface brightnesses) then it's generally the case that the larger emitter will require a larger reflector to match the throw of a smaller emitter.
to make it short:
the XM-L is the newer one and can give really MUCH light.
the SST is older, can give double than that really MUCH light but needs 4 times the power for it.
when both are inside a housing that can move the heat away from the led - that is necessary!!! -
the one with the XM-L will get really hot,
the one with the SST will get burning hot, coocing the led to death.
the XM-L (which is floody in itself) will give a "tighter" beam, while the SST will be some kind of a flood beam.
Like double (?) the diameter.
PS: I con not think of any battery source that might be able to power up the SST, when it really can be driven with 11 Amps.
Even the 2.8 A for the XM-L is hard for most setups (at least for some useable time)
the XM-L is the newer one and can give really MUCH light.
the SST is older, can give double than that really MUCH light but needs 4 times the power for it.
when both are inside a housing that can move the heat away from the led - that is necessary!!! -
the one with the XM-L will get really hot,
the one with the SST will get burning hot, coocing the led to death.
the XM-L (which is floody in itself) will give a "tighter" beam, while the SST will be some kind of a flood beam.
Like double (?) the diameter.
PS: I con not think of any battery source that might be able to power up the SST, when it really can be driven with 11 Amps.
Even the 2.8 A for the XM-L is hard for most setups (at least for some useable time)
MikeAusC
Enlightened
Both the XM-L and SST90 have Lambertian angular distribution - i.e. beamwidth of about 120 deg at 50% brightness.
The surface brightness + the size of the reflector is the key to throw. Take two leds and put them in a reflector, the one with the highest surface brightness will have the best throw in any reflector. The reflector shapes the beam, but it focuses on a "point source". If that point on the led is brighter, the hotspot will be brighter. All lights have better throw in hi mode than lo mode because surface brightness is better in hi mode.
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The die of SST-90 is 8mm diameter and the base is 10x11mm, this should be 50mm square die size?;
http://www.luminus.com/products/SST-90_2_3543760270.pdf
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MikeAusC
Enlightened
When talking about the image size etc all that matters is the silicon die size, which is 3 x3 mm for the SST-90 - the yellow square you can see through the lens. See page 9 of the Rev 7 Datasheet.
No, it doesn't look 3x3mm, but that's because it gets magnified by the lens.
No, it doesn't look 3x3mm, but that's because it gets magnified by the lens.
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MikeAusC
Enlightened
According to the SST-90 datasheet, the N3 bin delivers 950 to 1000 lumen at 3.15 amp.
the SST-90 has a much bigger die than the XML, so it will require a bigger reflector to get it to throw. The SST-90 can be driven at much higher currents, and can achieve higher output than the XML.
There aren't many flashlights using the SST-90, you are only gonna find SST-90 "searchlights" that are much bigger and bulkier. On the other hand XML are available on much smaller form factors such as 2xCR123.
I'm guessing that are considering the Olight SR90 vs SR92 or RRT-3 or TK70, since they are more or less in the same size category. Not that the XML models use 3 XML chips and will give you more output than a single SST-90.
There aren't many flashlights using the SST-90, you are only gonna find SST-90 "searchlights" that are much bigger and bulkier. On the other hand XML are available on much smaller form factors such as 2xCR123.
I'm guessing that are considering the Olight SR90 vs SR92 or RRT-3 or TK70, since they are more or less in the same size category. Not that the XML models use 3 XML chips and will give you more output than a single SST-90.
MikeAusC
Enlightened
The XM-L is 2x2mm, the SST-90 is 3x3mm - so does the reflector need to be 1.4mm wider ????
Please explain why, and by how much, the reflector needs to be bigger.
I don't really know how to calculate it but perhaps some expert could say, but it's not 1,4mm bigger it's more likely 30mm bigger (my guess is based on YouTube video looking at beampattern and size of the reflector). U'll need to take footprint size, die size, beamangle and surface brightness into consideration....
MikeAusC
Enlightened
If you take an XM-L out of a Reflector/Aspheric that shows a focussed image of the die, and replace it with an SST-90 with the same surface brightness, you will end up with -
- A hotspot that's 50% wider (3/2)
- A hotspot that has 2.2 times the area (9/4)
- A hotspot that's the same brightness.
It's simple geometry and physics.
- A hotspot that's 50% wider (3/2)
- A hotspot that has 2.2 times the area (9/4)
- A hotspot that's the same brightness.
It's simple geometry and physics.
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I think you'll need a much more wider reflector to compensate for the bigger die size.
jimmy1970
Flashlight Enthusiast
A closer comparison would be the Cree XML and the SST-50.
MikeAusC
Enlightened
Please explain why a 1.4mm increase in Die diagonal requires a "much more wider " reflector.
